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Imprinting, with special reference to anxiety Dillon, Peter John 1962

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i IMPRINTING, WITH SPECIAL REFERENCE TO ANXIETY by P. JOHN DILLON B.A., U n i v e r s i t y of London, 1 9 6 l A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS i n the Department of PSYCHOLOGY We accept t h i s t h e s i s as conforming to the standard r e q u i r e d of candidates f o r the degree of MASTER OF ARTS. THE UNIVERSITY OF BRITISH COLUMBIA August, 1 9 6 2 In presenting t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f the requirements f o r an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study. I f u r t h e r agree that permission f o r extensive copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the Head of my Department or by h i s r e p r e s e n t a t i v e s . I t i s understood t h a t copying or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be allowed without my w r i t t e n permission. Department of •/ZPfa — y The U n i v e r s i t y of B r i t i s h Columbia, Vancouver 8, Canada. Date /d ^ /ffa • i i ABSTRACT The general purpose of t h i s research was to investigate the behaviour of newly-hatched chickens during th e i r f i r s t few days of l i f e . Various degrees of s o c i a l i s o l a t i o n and of approximation to a normal environment were used, and special note was taken of t h e i r behaviour which might r e f l e c t the presence of anxiety i n the chicks. With:.these observations as a base-line, the behaviour of comparable chicks i n a t y p i c a l imprinting s i t u a t i o n was then examined, again with sp e c i a l reference to behavioural indices of anxiety. Based on both sets of observations, an analysis of the psychological processes underlying the behaviour i n the imprinting s i t u a t i o n was made. There were several reasons f o r proceeding i n t h i s manner: (1) Observation of chicks i n a non-experimental s i t u a t i o n provides knowledge of t h e i r usual behaviour, and thereby reduces the p r o b a b i l i t y that subsequent interpretations w i l l be a r t i f i c i a l , and that subsequent conclusions regarding th e i r behaviour w i l l be erroneous. (2) Unless record i s made of the usual behaviour of chicks i n a non-experimental s i t u a t i o n , i t i s not possible to assess the effect of any experimental procedure. (3) Reports i n the l i t e r a t u r e have usually indicated that behaviour i n the imprinting s i t u a t i o n i s characterized by f a i r l y stereotyped following of a moving object. Preliminary observations and discussion suggested that such reports were e n t i r e l y too narrow, and that other behaviour i n the s i t u a t i o n had been neglected. This other behaviour was f e l t to be as s i g n i f i c a n t as the following behaviour customarily reported. Both sets of observation provided abundant evidence that the behaviour of the chicks i n the imprinting s i t u a t i o n was not fundamentally d i f f e r e n t from t h e i r behaviour i n a less experimental environment, and confirmed the b e l i e f that the behaviour i n the imprinting s i t u a t i o n was not as r i g i d and narrow as usually reported. The several theories of imprinting were examined from t h i s wider point of view, es p e c i a l l y that of Howard Moltz (I960). Certain inconsistencies i n Moltz*s theory were d i s -cussed, and some alternative ideas, mainly concerning anxiety novelty and habituation, were introduced. V ACKNOWLEDGEMENT The writer is greatly indebted to his advisors, Dr. W. H. Read and Dr. L. G. Sampson for their active interest, helpful criticism, and valued comments during the course of this thesis. The generous advice and interest of Professor E. S. W. Belyea have been greatly appreciated, as has his assistance with the equipment used in the study. Mr. H. W. E l l i s , superintendent of the Poultry Farm at the University, kindly provided appropriate facilities for the observational part, and the subjects for the whole of the study. The members and graduate students of the Psychology Department have contributed many useful criticisms and comments—both positive and negative—concerning this area of research, and the writers grateful thanks are extended to them. My wife assisted greatly with the preparation of the thesis, and thanks of a special kind are due to her. i i i TABLE OF CONTENTS Chapter ^age Title page.. i Abstract i i Table of Contents i i i List of Tables iv Acknowledgement v I REVIEW OF THE RELEVANT LITERATURE, AND GENERAL STATEMENT OF THE PROBLEM 1 II METHODS AND PROCEDURES 80 (a) Outside the Imprinting Situation 80 (b) In the Imprinting Situation 90 III RECORD OF OBSERVATIONS 95 (a) Outside the Imprinting Situation..... 95 (b) In the Imprinting Situation 110 IV DISCUSSION OF THE OBSERVED BEHAVIOUR, WITH REFERENCE TO THEORIES OF IMPRINTING 1^ 6 V SUMMARY AND CONCLUSIONS 171 REFERENCES 175 i v LIST OF TABLES Table No. ' . Page L i s t of groups observed outside the i m p r i n t i n g s i t u a t i o n . 87 1 I CHAPTER I REVIEW OF THE RELEVANT LITERATURE AND GENERAL STATEMENT OF THE PROBLEM A. BACKGROUND Reports that chickens, ducks, geese, and other birds will follow a moving object other than their natural parents, within the f i r s t few hours or days after hatching, have appeared in scientific journals and quasi-scientific magazines since the latter half of the last century (Spalding, 1873; James, 1892; Craig, 1908; Heinroth, 1910). That such a thing happens is almost certain to have been known well before that. Since psychology as an experimental science had hardly begun to establish itself at the time of these f i r s t reports, i t is not surprising that l i t t l e systematic investigation of the observed phenomenon was performed, and since, for the most part, young birds were observed following their parents, and orienting much of their early behaviour towards them, interest lay more in the presumed instinctivehess of the almost universally observed parent-following than in those cases where the objects followed were other than the parents. However, i t is precisely because the birds soon after hatching can regularly be shown to follow these other objects—without receiving any of the usual rein-forcers of experimental psychology—that interest in the phenomenon now lies in its possibility as a case which requires | learning theory, the very core of psychology, to be seriously revised. 2 The basic task of learning theory is to determine the necessary and sufficient conditions for what is called learning to occur. To do this i t must establish a definition of what i t means when i t uses the term learning. These two problems are closely interwoven, i f not formally, then in the experimental procedures and the reasoning of those who are concerned with them--witness the perennial controversy over latent learning, and the tremendous divergence between S - R, S - S, and Gestalt theorists. Even i f a l l sides were to agree in labelling the process implied by the term 1perception' a response—which itself has been a major stumbling-block for many years—the contention would hardly be reduced, for, while some theorists believe that the perception of certain stimulus-complexes is a sufficient condition for learning to occur, others hold that some for in of reinforcement must accompany the response, (in this case the perception), i f learning is to occur. Stemming from this basic difference, several lines of investigation and further discussion have developed. Social reinforcers, secondary rewards, fractional-anticipatory-goal-responses, and the like, have been advanced on one side to account for what had been put forward as cases of learning-without-reinforcement, and on another side i t was suggested that some responses were self-reinforcing. Guthrie's suggestion that the function of rewards in certain escape situations was simply to remove the animal from the situation (and so to stop him making responses in that situation)—thereby preserving the 3 last response made, which was, of course, the one which made the exit possible—has always been a thorn in the flesh of reinforce-ment theorists. Again, the data on avoidance-conditioning have been arraigned against reinforcement theories of learning, and, more recently, much attention has been given to the behaviour of animals placed in a novel environment, in the absence of conven-tional reinforcers, and to their behaviour on subsequent exposures to the same environment. From the point of view of learning theory, three things have become very clear as the result of a l l this: f i r s t l y , that the earlier conceptions of reinforcement have become so extended, and applied in such a wide variety of ways', that i t is questionable whether, from an overall viewpoint, the term has much left in i t ; secondly, that the necessary and sufficient conditions for learning to occur have not been agreed upon; and thirdly, that no adequate definition has been formulated of the term learning. (As an illustration of this situation, see McConnell and Jacobson, 1962, pages k2 and k6 in particular.) Even without venturing into the neurophysiology of the matter, only some of the problems have been mentioned, and this state of affairs should be borne in mind in discussing imprinting phenomena and processes, and in investigating and theorizing about the relationship of these to learning and to instinct, as will be done later. k The position of i n s t i n c t theorists, both ancient and modern, must necessarily be considered before concentrating on what has been established concerning imprinting. The neonate organism has been the focus of attention here f o r the supposedly s u f f i c i e n t reason that i n the f i r s t observable items of behaviour, one must surely be witness to the expression of pure nature, untrammelled by the effects of experience. Two major d i f f i c u l t i e s have almost always been admitted, that the organism develops i n the f o e t a l (or equivalent) stage, and that certain items of behaviour do not appear u n t i l the organism i s r e l a t i v e l y old (e.g., courtship and reproductive behaviour), and then they appear at a given age, and i n a stereotyped form both of which are common to the species, even though some members may have been reared i n very d i f f e r e n t environments from others. Although the problem of the r e l a t i o n of prenatal and l a t e r maturational behaviour to the f i r s t behaviour of the neonate organism, and to the environment, has been admitted i n the past, i t i s only recently that i n t h i s very problem has been found the key to the f a l l a c i o u s instinct-versus-environment, or nature-versus-nurture dichotomy. Lehrman (1953) has dealt probably the most i n c i s i v e blow to the t r a d i t i o n a l dichotomized outlook, and i t i s a tribu t e to the s c i e n t i f i c i n t e g r i t y of the latter-day i n s t i n c t i v i s t s , the Eth o l o g i s t s , that they have recognized the meaningfulness of h i s c r i t i c i s m s , and have since formulated th e i r theories i n such a way that the 5 problems which were unseen, ignored, or glossed-over, have now been taken into account, (e.g., Lorenz, 1951*; Tinbergen, 195*+«) Hebb, too, has been concerned to bring out the d i f f i c u l t i e s involved here (1953, 1958). Before discussing Lehrman's po s i t i o n , however, i t i s well to consider some opponents i n the t r a d i t i o n a l nature-nurture controversy. McDougall's i n s t i n c t theory (1923, f o r example) may be set up as the prime example of the 'nature' p o s i t i o n . According to McDougall there are numerous i n s t i n c t s which are given expression i n much, i f not most, of an organism's behaviour. In other words, observable behaviour at any given stage r e s u l t s not from the past experiences of the organism, and from what i t has learnt i n and from those experiences, but rather from s p e c i f i c inborn i n s t i n c t s . I t i s not denied, of course, that a reasonably adequate environment i s necessary f o r these i n s t i n c t s to operate, just as an adequate environment i s necessary f o r the physical structures and c h a r a c t e r i s t i c s of the organism to develop, but the r S l e of the environment i s seen as e s s e n t i a l l y that of providing a medium i n which both the physical features and the behavioural features w i l l be manifested. A p a r t i a l l i s t of these i n s t i n c t s reads as follows: a) The parental or protective i n s t i n c t , b) The i n s t i n c t of combat, c) The i n s t i n c t of c u r i o s i t y , 6 d) The food-seeking i n s t i n c t , e) The i n s t i n c t of repulsion, and so f o r t h (pp. 130-165). I t w i l l be seen that these are not behavioural items i n a molecular sense, but rather are molar forms, or classes of behaviour. Training and experience can operate within these classes influencing the means adopted to achieve the pa r t i c u l a r e n d — f o r example, i t may be the custom i n some parts to duel rather than to use f i s t s or gloves, and hence the i n s t i n c t of combat would f i n d i t s expression i n the former rather than the l a t t e r f a s h i o n — b u t the i n s t i n c t s provide the urge to action, or they are, i n McDougall's words, the "springs of energy" (p. 105). The main d i f f i c u l t y with such a theory i s brought out when the i n s t i n c t s become numerous (as they did i n the case i n question), f o r then i t becomes apparent that whatever the organism does, and whatever i t does not do, are both nothing but the expression of the respective i n s t i n c t s — t o c i t e the much used example: i f he twiddles h i s thumbs i t i s the "thumb-twiddling" i n s t i n c t , while i f he does not twiddle h i s thumbs, i t i s the "thumb-not-twiddling" i n s t i n c t , and so on. Now, although McDougall's l i s t of i n s t i n c t s r e f e r s to CLASSES of behaviour, e s s e n t i a l l y the same c r i t i c i s m can j u s t l y be le v i e d against i t , on two grounds, f i r s t l y , because there i s i m p l i c i t i n the discussions of the various i n s t i n c t s , reference to, or a meaning which includes, s p e c i f i c molecular behavioural 7 items or units, e s p e c i a l l y with regard to the lower animals. This probably stems, i n the f i r s t instance, from the necessary condition that structure l i m i t s function, but whatever i t s raison d'etre, i t s presence i s f e l t continuously; secondly, because of the very f a c t that the i n s t i n c t s l i s t e d r e f e r to classes of behaviour, the determination of the molecular units which are subsumed within the classes becomes so subjective and personalized that i f each item i s taken separately, i t would be d i f f i c u l t to assign i t to a unique c l a s s , hence one has to look fo r a c r i t e r i o n of assignment beyond the behaviour of the organism. To some theorists of philosophical bent t h i s has been p e r f e c t l y acceptable, but McDougall i n s i s t s that the d e f i n i t i o n of each i n s t i n c t ( i . e . , of each class) l i e s i n i t s motor expressions (p. 118), which accordingly j u s t i f i e s the second c r i t i c i s m above. At the extreme opposite viewpoint was Kuo, who e n t i t l e d one of h i s papers (192*0, MA Psychology without Here-d i t y , " and who provided much experimental evidence i n support of h i s p o s i t i o n (e.g., 1930; 1932). His argument i s well summarized i n t h i s quotation (1930,: p 33): In other words, the kinds and range of potent i a l responses of an organism are deter-mined by i t s bodily s i z e , and e s p e c i a l l y i t s bodily make-up or organismic pattern, (he stresses that he does not mean neural pattern, P. J. D.), while i t s actual responses are determined by i t s l i f e h i s t o r y . Given an organ-ismic pattern, i t s behavior can be modified at w i l l by manipulating i t s l i f e conditions. 8 An important point to note i s that by l i f e h i s t o r y Kuo means from f e r t i l i z a t i o n to death, not from b i r t h to death. In a passage immediately preceding the one just quoted he says, ( r e f e r r i n g to cats whose behaviour with respect to rats he had been investigating,, ; p. 33): Its behavior i s being modified from the moment of f e r t i l i z a t i o n to the point of death, and i s modified according to the resultant forces of environmental stimulation, i n t r a -organic as well as extra-organic. In the same paper he asks.(p. 33)• Have the cat and t i g e r any i n s t i n c t s ? Does the chimpanzee possess any insight? Is the cat's behaviour towards the r a t hereditary or learned through t r i a l and error, or by imitation? To me a l l such questions are use-les s as well as meaningless. This i s Behaviourism i n the Watsonian t r a d i t i o n which, with varying degrees of re - i n t e r p r e t a t i o n and/or damping, i s i m p l i c i t i n much of present-day psychology. His disturbance at the s u p e r f i c i a l i t y of the arguments and i n v e s t i -gations of those who were concerned to enumerate and demonstrate the i n s t i n c t s of man or other animals can be f e l t i n th i s l a s t quotation from the same source;(pp. 3^ -35)* The point I am here making i s that the mere proof or disproof of an i n s t i n c t , i . e . , action which can be performed without learning, the mere experiments on t r i a l and error learning and the mere test to show the presence or absence of ins i g h t or i n t e l l i -gence and im i t a t i o n w i l l not lead us anywhere. 9 We need to know the p o t e n t i a l range or repertory of a c t i v i t i e s of a given species. We need to know the physiological and genetic or developmental aspects of each behaviour. The behaviour of an organ-ism i s a PASSIVE a f f a i r , (Kuo's emphasis). How an animal or man w i l l behave i n a given moment depends on how i t has been brought up and how i t i s stimulated. Without s u f f i c i e n t knowledge of the physiology of behaviour and of the behaviour h i s t o r y of the organism, prediction would be imposs-i b l e . Our study shows that kittens can be made to k i l l a r a t , to love i t , to hate i t , - t o fear i t , or to play with i t : i t depends on the l i f e h i s t o r y of the k i t t e n . In the future with more refined methods, with more thorough in v e s t i g a t i o n i n t h i s d i r e c t i o n , and with more knowledge of the physiology of the cat's behaviour, we should be able to predict i n mathematical terms how a given cat w i l l react to a given r a t at a given moment. Our behaviour researches i n the past have been i n the wrong d i r e c t i o n , because INSTEAD OP FINDING HOW WE GOULD BUILD NATURE INTO THE ANIMAL, WE HAVE TRIED TO FIND NATURE IN THE ANIMAL, (Kuo*S emphasis). The comparison between the ideas of McDougall and Kuo throws one aspect of the controversy i n t o sharp r e l i e f . To compare the ideas of Lorenz (1937) and Moltz (i960) on im-p r i n t i n g w i l l i l l u s t r a t e how, even up to the present day, the conceptual dichotomy between i n s t i n c t and learning p e r s i s t s despite the arguments, investigations, and pleas of many who see the fallaciousness and emptiness of such a d i v i s i o n . Lorenz has more recently modified h i s e a r l i e r p o sition on a number of counts, l a r g e l y due, as mentioned e a r l i e r , to the c r i t i c i s m s of Lehrman, which w i l l be discussed i n a moment, and to some 10 recent experimental evidence which indicates that some of the ch a r a c t e r i s t i c s of imprinting suggested by Lorenz are not as clear-cut as was thought. These too w i l l be referred to l a t e r . Since, however, t h i s contrast i s intended mainly to provide the background to which investigations of imprinting belong ( i n -cluding the one reported here), as well as opening the discussion of imprinting i t s e l f , and further, since Lorenz 1s e a r l i e r writings express the s p i r i t of the Ethologists* approach to such matters, these early writings w i l l be quoted here i n contrast to Moltz*s apparently d i f f e r e n t viewpoint. Lorenz (1937)- claims that imprinting d i f f e r s from learning i n four respects;.(pp. 2^ 9-251): 1. The process i s confined to a very d e f i n i t e period of i n d i v i d u a l l i f e , a period which i n many cases i s of extremely short duration;.... 2. The process, once accomplished, i s t o t a l l y i r r e v e r s i b l e , so that from then on, the reaction behaves exactly l i k e an 'unconditioned' or purely i n s t i n c t i v e response. This absolute r i g i d i t y i s something we never f i n d i n behaviour acquired by associative learning, which can be unlearned or changed, at l e a s t to a c e r t a i n extent. 3. The process of acquiring the object of a reaction i s i n very many cases completed long before the reaction i t s e l f has become established, h. In the process of imprinting, the i n d i v i d u a l from whom the stimuli which influence the con-di t i o n i n g of the reaction are issu i n g , does not necessarily function as an object of t h i s reaction. 11 Moltz ( i 9 6 0 ) , on the other hand, contends that imprinting consists of two learning processes, operating on d i f f e r e n t expo-sures to the experimental s i t u a t i o n (p. 3 0 5 ) s I t i s assumed that during the c r i t i c a l p e r i o d . . . ( c l a s s i c a l ) * conditioning of...low-anxiety reactions occurs simply by virt u e of t h e i r association with the object, and does not i n any way depend upon reinforcement. However, as a r e s u l t of this conditioning the object acquires the capacity to function as a r e i n f o r c e r , henceforth mediating new learning. S p e c i f i c a l l y , i t i s assumed that when anxiety i s subsequently aroused, any response i n s t r u -mental i n bringing the animal i n t o contact with the f a m i l i a r object w i l l be c l o s e l y followed i n time by anxiety reduction due to the previously acquired capacity of the object to e l i c i t responses incompatible with anxiety. I t should be noted that the two analyses are not as f a r apart as they at f i r s t seem. I t i s more the case that each emphasizes a d i f f e r e n t aspect from the other. Lorenz i s concerned to show that on the f i r s t exposure the animal i s at a maturational stage at which certain "innate perceptory patterns" are f u n c t i o n a l l y capable of e l i c i t i n g behaviour with respect to c e r t a i n stimulus objects i n the environment, much as "inductive determination" designates the process by which, at a very s p e c i f i c (early) stage i n embryonic development, "transplanted c e l l s owing to influences emanating from their new environment, are induced to develop i n a way f i t t i n g to i t , and not i n the way they would have developed i n their o r i g i n a l p o s i t i o n . " (Lorenz, op. c i t . ) * Moltz*s brackets. 12 The stimulus object i n the environment, which e l i c i t s the behaviour, i s thought of as having cer t a i n properties which match those of the innate perceptory patterns, but also the external stimulus has other properties not "given" i n the innate percep-tory pattern, and the behaviour which i s e l i c i t e d upon exposure to the external stimulus i s the r e s u l t of two processes: i n the f i r s t place the behaviour i s "triggered-off" by the corres-pondence between certa i n properties of the stimulus object and those of the innate perceptory pattern; and secondly, the behaviour i s conditioned to whatever other c h a r a c t e r i s t i c s the external stimulus object may have but which are not "given" i n the innate perceptory pattern. This l a t t e r process of conditioning has not featured i n discussions by psychologists of Lorenz's.views on imprinting to anything l i k e the extent to which the innate per-ceptory patterns have. The reason for t h i s i s not hard to f i n d . The conditioning process may be said to be akin to,processes of the same name postulated by behavioural psychologists, whereas to many psychologists the postulate of an innate perceptory pattern as an explanation of the mechanism of a causal r e l a t i o n s h i p i s anathema. I t smacks of mysticism and appears both gratuitous and useless to a behaviourist. I t seems to mean that, i n some way, the animal i s born into the world having within i t some kind of preview of what i t w i l l meet i n the world, as well as an automatic connection between this innate preview and i t s motor organs, whereby i t automatically produces a f u l l y - i n t e g r a t e d , 13 adaptive response pattern on f i r s t coming int o contact with the p a r t i c u l a r object. While such postulates may, i n a l i t e r a r y sense, account for the observed behaviour, i t i s f e l t that they do not do so i n a functional sense. The sort of approach which i s taken to be more r e a l i s t i c depends upon a developmental analysis of the changing structure, constant structure, changing physiology, constant physiology, changing environment and constant environment of the animal, as well as upon observations on the i n t e r r e l a t i o n s and i n t e r a c t i o n within these several aspects of the organism, and between these and observed behaviour ( i . e . , the constant and the changing functions of the organism i n a given past and present s e t t i n g ) . This sort of approach has been mentioned i n discussing Kuo*s p o s i t i o n , and i t w i l l be referred to again with regard to Lehrman's c r i t i c i s m s of i n s t i n c t theories. Moltz, however, despite h i s main argument that imprinting can be adequately accounted for i n terms of two d i f f e r e n t types of learning process, does have to introduce apparently inborn, species-specific properties of the maturational processes which he i n f e r s from h i s observations of the a n i m a l ^ behaviour. The difference between these and. Lorenz *s postulate of innate perceptory patterns does not r e s t e n t i r e l y upon the d i f f e r e n t implications of the two sets of postulates, but also upon the terms i n which they are couched. Moltz suggests that -anxiety towards strange objects i s not present i n the a n i m a l — Ik to the extent that i t s overt expressions can be observed, at l e a s t — d u r i n g i t s f i r s t exposure to the imprinting apparatus at a few hours of age, whereas, he says, i t Is present, and i t s overt manifestations are observable, during the second exposure a day l a t e r . In other words, the referrent of the term •anxiety* develops at a f a i r l y s p e c i f i c period i n ontogeny, that i t i s not present before t h i s period, and that i t diminishes afterwards. Not only that, but the stage at which i t appears varies with d i f f e r e n t species, (see p. 296, Moltz agreeing with t h i s i n t e r p r e t a t i o n made by Hinde, Thorpe, and Vince, 1956)* I t i s a matter of concern here whether the l a b e l 'anxiety* has become such an every-day part of psychology— whereas such terms as *innate perceptory pattern*, 'innate releasing mechanism*, or more recently, 'releasing mechanism', and ' s p e c i f i c action p o t e n t i a l ' , which have become common-place i n Ethology, but have not i n Psychology—that the former term i s accepted while the l a t t e r ones are rejected l a r g e l y because the former i s not subjected to continuous c r i t i c a l appraisal, while the l a t t e r are. I t i s f e l t that the former, as a l i n g u i s t i c l a b e l designating an inference, or a hypothetical construct, from observed behaviour, have many of the same implications as the l a t t e r terms, which are likewise inferences, or hypothetical constructs from observed behaviour. But whereas the l a t t e r terms are generally unacceptable because of these implications, the former terms are accepted, and these same implications ignored,, 15 With t h i s i n mind the two theories may be pictured somewhat as follows: both include an ethereal postulate together with a learning process (that t h i s too i s poorly defined was mentioned e a r l i e r ) . In Moltz 1s case there are two learning processes. For Lorenz the learning process appears to operate independently of, although simultaneously with, the postulated 'innate perceptory p a t t e r n 1 , and i s not necessary to account f o r the following per se f (since t h i s i s triggered-off by the correspondence between c e r t a i n c h a r a c t e r i s t i c s of the external stimulus and those of the innate perceptory pattern). For Moltz the postulated 'anxiety 8 features as part of both learning processes. On the f i r s t exposure the low anxiety i s conditioned to the target-object,* and on the second exposure, since the target-object i s now associated with low-anxiety, -whereas the re s t of the imprinting environment evokes high anxiety,.following the moving target-object serves to reduce the animal's anxiety. One further point with regard to the actual s i m i l a r i t y between the two positions, despite t h e i r l i n g u i s t i c divergence: Lorenz (1955) flow considers that h i s e a r l i e r d i s t i n c t i o n between imprinting and conditioning should not be stressed; he suggests that the two should be thought of as continuous rather than as discrete processes. The term 'target-object* i s used simply as a convenient shorthand means of describing the object followed, or to be followed. 1 6 I t i s appropriate to turn now to Lehrman's ( 1 9 5 3 ) c r i t i c a l discussion of i n s t i n c t theories, which focusses upon the two very similar theories of Lorenz and Tinbergen (e.g., Tinbergen, 1 9 ^ 2 ) . The most relevant problem raised and discussed i s that of the "innateness" of behaviour. Lehrman f i r s t examines the way i n which Lorenz and Tinbergen use the terms innate and i n h e r i t e d , and summarizes t h i s as follows: I t i s thus apparent that Lorenz and Tinbergen, by 'innate' behaviour, mean be-haviour which i s h e r e d i t a r i l y determined, which i s part of the o r i g i n a l c o n s t i t u t i o n of the animal, which arises quite indepen-dently of the animal*s experience and - -environment, and which i s d i s t i n c t from acquired or learned behaviour. I t i s also apparent, e x p l i c i t l y or im-p l i c i t l y , that Lorenz and Tinbergen regard as the major c r i t e r i a of innateness that: ( 1 ) the behaviour be stereotyped and con-stant i n form; (2) i t be c h a r a c t e r i s t i c of the species; ( 3 ) i t appear i n animals which have been ra i s e d i n i s o l a t i o n from others; and (*+) i t develop fully-formed i n animals which have been prevented from pr a c t i c i n g i t . He then goes on to say: Undoubtedly, there are behaviour patterns which meet these c r i t e r i a . Even so, t h i s does not necessarily imply that Lorenz's INTERPRETATION (Lehrman's emphasis, P. J.D.) of these behaviour patterns as •innate' offers genuine aid to a s c i e n t i f i c understanding of t h e i r o r i g i n and of the mechanisms underlying them. 17 After examining several behaviour patterns which do i n f a c t meet these c r i t e r i a , and which have been analyzed i n great d e t a i l at successive embryonic stages, with p a r t i c u l a r regard to the organization of body components, the d i s t r i b u t i o n of forces ( e s p e c i a l l y those emanating from the rhythmic contractions of the heart), and the resultant stimulation and passive movement of the body components (see Kuo, 1932, concerning the development of pecking movements i n chickens), Lehrman concludes: The behaviour patterns concerned are not unitary, autonomously developing things, but rather they emerge ontogenetically i n complex ways FROM THE PREVIOUSLY DEVELOPED ORGANIZATION OF THE ORGANISM IN A GIVEN SETTING. (Present writer's emphasis). One of the conditions which i s normally claimed as being e s s e n t i a l to the proof that an observed behaviour pattern i s innate i s that the animal exhibiting i t must have been reared continuously i n i s o l a t i o n from other members of h i s species. That t h i s proves nothing of the kind i s aptly brought out i n the following passage from the same source: I t must be r e a l i z e d that an animal r a i s e d i n i s o l a t i o n from fellow-members of h i s species IS NOT NECESSARILY ISOLATED FROM THE EFFECT OF PROCESSES AND EVENTS WHICH CONTRIBUTE TO THE DEVELOPMENT OF ANY PARTICULAR BEHAVIOUR PATTERN. The important question i s not 'Is the animal i s o l a t e d ? 1 but 'FROM WHAT i s the animal i s o l a t e d ? 1 (Emphasis i s Lehrman 1s). 18 To bring out the flaw by means of a more v i v i d example, suppose the question were asked of a chemist, "Is the behaviour of t h i s element innate?" How would he set about answering i t ? The f a c t that the question would not normally be phrased i n t h i s way does not deny, of course, the v a l i d i t y of i t s meaning. Suppose the chemist kept a single unit of the element locked i n a box away from a l l other units of the same element. Suppose then that he l a t e r unlocked i t , and introduced i t into a given experimental environment. The r e s u l t was that i t underwent a c e r t a i n change, and that whenever he repeated thi s procedure with other units of t h i s element, they a l l underwent the same change. Would he then conclude that the behaviour i s innate? Would he not rather begin a more inten-sive study of the atomic organization of the element, both before i t was locked i n the box and a f t e r i t was removed from i t (and while i t was i n the box, i f he could conveniently do so without changing, by h i s examination, the very thing he was examining)? Would he not likewise investigate the physical and chemical properties of the environment at each stage? I f he d i d a l l t h i s , i t i s doubtful whether h i s f i n a l conclusion would be that the behaviour i s innate, but instead, he would describe the i n t e r a c t i o n within the element of i t s various properties, and between these and the properties of the environ-ment over the temporal sequence involved (including the time when the element was placed i n the experimental environment and 1 9 underwent the observed change), and out of t h i s he would have arrived at and causally explained trie behaviour i n question. With reference to t h i s type of developmental analysis of behaviour which has been subsumed under the headings innate or i n s t i n c t i v e , Carmichael ( 1 9 2 7 ) , and Lashley ( 1 9 3 8 ) also conclude i n i t s favour, although the former find s some objection to Kuo's presentation. Beach ( 1 9 5 5 ) contends: When these methods have been applied to the various types of behaviour which today are c a l l e d " i n s t i n c t i v e " , the concept of i n s t i n c t w i l l disappear, to be replaced by s c i e n t i f i c a l l y v a l i d and useful explanations. Whatever changes i n s t i n c t t h e o r i s t s have made i n the i r theories i n the face of t h i s sort of c r i t i c i s m , they have r i g h t l y i n s i s t e d that the type of behaviour under consideration, whether or not i t should be c a l l e d innate or i n s t i n c t i v e , does pose a unique challenge to a l l those concerned with the explanation of the causation of behaviour. I t can r e g u l a r l y be shown that i t occurs within a given species, i n stereotyped form, that learning and t r a i n i n g i n the conventional sense have played no part i n i t s development, and that i t i s not dependent for i t s i n i t i a l occurrence upon conventional reinforcement. In meeting t h i s challenge i t i s clear that the most important factors to be considered are those numbered by Hebb ( 1 9 5 8 ) as factors 1 , 2 , and k i n h i s l i s t (p. 1 2 1 ) — t h e genetic f a c t o r , deriving from the physiological properties of the f e r t i l i z e d 20 ovum; the prenatal chemical fa c t o r , deriving from n u t r i t i v e or toxic influences i n the uterine environment; and the constant sensory f a c t o r , deriving from the pre-and postnatal experience normally i n e v i t a b l e f o r a l l members of the species. Factor 3, the postnatal chemical f a c t o r i s presumably of less importance i f the behaviour i n question occurs immediately at b i r t h , but since most observations are made some hours, or even some minutes, aft e r birth,the relevance of t h i s factor should not be minimized. A case i n point i s that of imprinting i t s e l f — t o the writer's knowledge, there has been no mention of a certa i n factor of t h i s class which might well be expected to contribute to the f a c i l i t a t i o n of imprinting ( i n both a l i t e r a r y , and a psychological sense) namely that of heat l o s s — h e a t production. The r e l a t i o n between heat loss and movement i s well established i n physiology, and since the chick, on the f i r s t exposure, i s only a few hours old, i s p r o b a b l y s t i l l damp to some degree, and i s removed from the heat of i t s l i v i n g quarters and placed i n a somewhat colder area without a d i r e c t external heat source, there i s every reason to expect that i t w i l l show a s i g n i f i c a n t amount of movement. This does not mean to imply, of course, that i t w i l l thereby run afte r the target object, but i t does imply that once i t does so, the extra heat produc-t i o n within the animal w i l l contribute to the continuance and strenghthening of t h i s response, i n much the same way, but i n the opposite d i r e c t i o n , that Moltz suggests anxiety reduction reinforces the response. Whereas anxiety i s a somewhat vacuous 2 1 concept, heat changes do at l e a s t lend themselves to objective measurement and manipulation, and, being something other than the behaviour i n question, (although a suggested causal f a c t o r i n that behaviour), avoid the danger of c i r c u l a r argument. This i s one thing which came out of the observations of the behaviour of the animals both within the imprinting s i t u a t i o n , and outside i t , and should not appear here, perhaps, but i t does i l l u s t r a t e the importance of factor 3 . [N.B. Although temperature i s a physical f a c t o r , rather than s t r i c t l y chemical, i t c l e a r l y belongs under t h i s heading; see Hebb's ( 1 9 5 8 ) discussion of the way i n which the factors are grouped, pp. 1 2 0 -1 2 6 . ] Although b i r t h i s commonly re f e r r e d to, i n psychoanalytic l i t e r a t u r e , as a traumatic event, or even as the most traumatic event—leading to f e e l i n g s of r e j e c t i o n and so f o r t h — i t cannot be included under Factor 6 , even though i t may normally involve the destruction of c e l l s , since i t i s c e r t a i n l y not one of an 'abnormal 1 class of events to which an animal might conceivably never be exposed (Hebb, OP. c i t . ) . The changes constituting and r e s u l t i n g from b i r t h w i l l be amongst the most relevant to the causation of immediate postnatal behaviour, an obvious point, but one which has been l a r g e l y ignored by at l e a s t the e a r l i e r i n s t i n c t t h e o r i s t s . This then i s the background to, and setting of, the present study of early development i n the chick. I t i s an important factor underlying the adoption of the present 22 procedure. This procedure demands that the behaviour of the chick, outside the experimental imprinting s i t u a t i o n , but i n various kinds of more-or-less normal s i t u a t i o n , be examined with a view to establishing a baseline against which to compare the chick's behaviour i n the more experimental imprinting s i t u a t i o n . Above a l l , i t emphasizes the close continuity between observation and experimentation, and i t reduces the pr o b a b i l i t y that interpretations and theories of imprinting behaviour w i l l be a r t i f i c i a l . B. THE LITERATURE RELEVANT TO IMPRINTING Most investigations of imprinting took place i n the 1 9 5 0 ' s , the most important exceptions being Spalding's observations i n 1 8 7 3 , Heinroth's work, reported i n 1 9 1 0 , and Lorenz's and Bruckner's studies i n the 1 9 3 0 ' s . Beach and Jaynes, i n 1 9 5 * + , discussed the effects of early experience upon the behaviour of animals, and Moltz, i n i 9 6 0 , reviewed the l i t e r a t u r e on imprinting i n connection with the theory he was proposing to account for the e f f e c t s of the experimental procedure Involved. Hinde ( 1 9 6 l ) provides an excellent discussion of parent-offspring r e l a t i o n s , which focusses upon imprinting. Due to Haldane's in t e r e s t i n Spalding's work, i t was republished i n 1 9 5 ^ and thereby was brought d i r e c t l y to the attention of contemporary behavioural s c i e n t i s t s . Spalding pointed out that newly-hatched chickens tend to press against 23 many objects, i n t e r p r e t i n g t h i s as due to th e i r need f o r warmth. This was confirmed by C o l l i a s (1952) who reported that contact with a human hand, f i f t e e n minutes afte r hatching, diminished the animal's d i s t r e s s c a l l s . C o l l i a s also found that there were fewer such c a l l s when the birds were hatched at higher, rather than lower, temperatures, and that they were s i m i l a r l y reduced i n the presence of the clucking of a hen. He noted that the introduction of a moving object at t h i s time (15 minutes a f t e r hatching) did NOT lead to reduced d i s t r e s s c a l l i n g , although i t d i d have t h i s r e s u l t an hour l a t e r . Spalding reported that chicks reared i n a f l a n n e l bag, with hoods and ear-plugs, on f i r s t having these removed and being placed a few feet from a hen, ran to the hen. This does not occur af t e r the chicks are eight hours old, i f they have not seen, the hen before then. (Wood-Gush (1955) c i t e s Bruckner, 1933 > as confirming t h i s . ) According to Spalding, chicks, blindfolded from hatching to between one and three days thereafter, i n s t i n c t i v e l y preened themselves and scratched the ground when their v i s i o n was freed, and showed fear or suspicion of stinging insects at th i s time, but would attempt to catch f l i e s . They would peck at many small objects, including t h e i r own excreta. This l a t t e r point i s confirmed i n the observations to be reported, but the present writer found that chicks, not blindfolded from 2h b i r t h , showed a s t a r t l e response, (to be described i n d e t a i l i n Chapter I I I ) , to f l i e s and suchlike which happened to f l y near them, and continued to watch their movements, but made no attempt to catch them. I t i s possible that Spalding's chicks on t h i s occasion were older than those observed by the present writer, apart from the difference i n their v i s u a l experience. Both Spalding's and the present writer's chicks did not drink water without f i r s t having pecked at bubbles i n the water v i s i b l e through the glass container, and through the water i t s e l f . With regard to fear, Spalding notes that a chick, 12 days old, gave a danger c a l l when a sparrow-hawk flew overhead, and a week-old brood took cover i n the presence of the same stimulus. (See Melzack et a l . , 1959, f o r a f i r s t -rate i n v e s t i g a t i o n of t h i s matter.) Bruckner (OP. c i t . ) found that chicks of less than seven days old show fear at a loud noise and at loss of equilibrium. C o l l i a s (OP. c i t . ) reports that the approach of a large object would e l i c i t d i s t r e s s c a l l s i n week-old birds, but that t h i s reduced such c a l l s when the animals were one hour old. Chicks show attachment to humans or other objects, which are moving, when they are just able to walk. I f b l i n d -folded from b i r t h u n t i l the encounter with humans, the chicks show no fear of them i f the i n i t i a l encounter i s when the chicks are between one and three days old; i f they are four days old, they show terror at such an encounter. (Spalding, OP. c i t . ) 2 5 Bruckner (on. c i t . ) reported that chicks brooded by a hen showed fear e a r l i e r than those a r t i f i c a l l y brooded. Both Bruckner and C o l l i a s state that chicks recognize their own hen by auditory and v i s u a l means, but hens generally do not recog-nize t h e i r own chicks i n d i v i d u a l l y . The c a l l s of the chick are more e f f e c t i v e than i t s movements i n e l i c i t i n g a i d from the hen. With regard to the much discussed question of whether the chick's pecking i s due to maturation of learning, i t i s i n t e r e s t i n g to note that Spalding's observations were so acute that he arrived at e s s e n t i a l l y the same conclusion as did Cruze ( 1 9 3 5 ) as a r e s u l t of the l a t t e r ' s systematic experimenta-t i o n : Spalding saw that chicks blindfolded from hatching, with the b l i n d f o l d removed at between one and three days of age, pecked f a i r l y accurately within f i f t e e n minutes, but that the r e s t of the feeding behaviour ( i . e . , holding the object i n the mouth while r a i s i n g the b i l l , and swallowing) was l e s s e f f i c i e n t . Cruze likewise found that accuracy i n i n i t i a l pecking increases with the age of the chick at the f i r s t t r i a l , (although practice quickly increases t h i s accuracy f u r t h e r ) . Accuracy of the t o t a l response, however, depends l a r g e l y upon the amount of practice, although older chicks require l e s s practice i n the t o t a l response to achieve a given degree of accuracy than do younger ones. Swallowing, when material i s i n the mouth, appears to be r e f l e x i v e , and Kuo ( 1 9 3 2 ) indicates 26 that i t occurs before hatching. Some of these forms of behaviour may not appear to be r e l a t e d to imprinting. One of the arguments to be presented i n Chapters IV and V, however, i s that the form of behaviour which t y p i c a l l y characterizes th i s imprinting, namely following, i s f a r from being the only, or even the t y p i c a l form of behaviour shown i n the presence of the target object. Such other behaviour always includes watching, often includes pecking, both at the object and at the ground while i n the v i c i n i t y of, or following the object, and may include running to the walls. I f t h i s Is so, then i t i s appropriate to consider what has been reported concerning the development of these items of behaviour, and concerning the range of objects to which they have been shown, as well as the conditions i n the respective experiments. Lorenz's work, ( 1 9 3 7 ) » has been mentioned already, but i t i s well to extract from h i s writings the data on which h i s theory i s based. This i s p a r t i c u l a r l y useful since the data, th e i r i n t e r p r e t a t i o n , and their discussion are often c l o s e l y interwoven i n h i s presentation. To do t h i s , the general and non-specific statements which imply but do not describe experi-ments and t h e i r resultant data w i l l be ignored, as w i l l the hypothetical or conditional sentences which suggest that c e r t a i n f a c t s have been, or could be established, but which do not provide s p e c i f i c evidence to that end. While t h i s may be an i n j u s t i c e to the way i n which Lorenz presents h i s work, i t i s 27 nevertheless e s s e n t i a l i f the evidence i s to be c r i t i c a l l y -appraised. He says;(pp. 2^7-252): Heinroth f a i l e d to breed hand-reared Great Horned Owls, Ravens, and other birds, f o r no other reason than that these tame i n d i v i d u a l s responded sexually to t h e i r keepers instead of to each other. P o r t i e l j e , of the Amsterdam Zoological Gardens, r a i s e d a male of the South American B i t t e r n (Tigrisoma) who, when mature, courted human beings. When a female was procured, he f i r s t refused to have anything to do with her but accepted her l a t e r when l e f t alone with her f o r a considerable time. The birds then successfully reared a number of broods, but even then P o r t i e l j e had to r e f r a i n from v i s i t i n g the birds too often, because the male would, on the appearance of the former fo s t e r - f a t h e r , i n -stantly rush at the female, drive her roughly away from the nest and, turning to h i s keeper, perform the ceremony of n e s t - r e l i e f , i n v i t i n g P o r t i e l j e to step into the nest and incubateJ I once had a pair of Greylag Geese hatch a Muscovy Duck's eggs. The parent-child r e l a -tions i n t h i s a r t i f i c i a l family dissolved sooner than i s normal f o r any of the two species, owing to some hitches i n mutual under-standing which occurred because...(theoretical explanation).... From the seventh week of t h e i r l i f e , however, the young Muscovies had nothing more to do with t h e i r former f o s t e r -parents, nor with any other Greylag Geese, but behaved s o c i a l l y toward one another, as well as toward other members of t h e i r species as a per f e c t l y normal Muscovy Duck should do. Ten months l a t e r the one male b i r d among these young Muscovies began to display sexual reactions and, to our surprise, pursued Greylag Geese i n -stead of Muscovy Ducks, s t r i v i n g to copulate with them, but he made no d i s t i n c t i o n between male and female geese. 28 In 1 9 3 6 , I kept a young Greylag i s o l a t e d from i t s kind f o r over a week, so that I could be sure that i t s following-reaction was se-curely attached to human beings. I then transferred t h i s young goose to the care of a Turkey hen, whom i t soon learned to use as a brooding-Kumpan f o r warmth instead of the e l e c t r i c apparatus i t had hitherto favoured. The gosling then followed the Turkey hen, pro-vided that I was not i n sight, and kept t h i s up f o r a f o r t n i g h t ; but even during that time I had only to walk near the two birds, to cause the gosling to abandon the hen and follow me. I did t h i s but three times to avoid conditioning the gosling to myself as a leader. When, af t e r two weeks, the gosling began to become more independent of the warming function provided by the Turkey hen, i t l e f t her and hung around our front door, waiting f o r a human being to emerge and trying to follow i t when i t did so. Now t h i s gosling, excepting the few necessary t r i a l runs, each of which did not l a s t more than about a minute, had never a c t u a l l y con-summated i t s following-reaction with a human fo r i t s object. On the other hand, fo r more than two weeks, i t had been i n constant contact with the Turkey hen; yet i t s following-reaction did not become conditioned to the Turkey i n pre-ference to the human. I would even suspect that i t s i n s t i n c t i v e following-reaction was never r e a l l y released by the Turkey at a l l , and that i t s following the hen was predominantly a purposive act, directed to the necessity of getting a warm-up from time to time. I t never ran d i r e c t l y a f t e r the Turkey hen i n the inten-sive way i n which i t would follow me and i n which Greylag goslings follow their normal parents, but just kept near her i n a most casual and deliberate sort of way, quite d i f f -erent from the normal reaction. I began experimenting by having Mallards hatched by a Muscovy Duck, with the r e s u l t that they ran away from her as soon as they could, while she continued incubating on the empty s h e l l s . Foster-mother and young f a i l e d com-pl e t e l y to respond to each other. Heinroth had exactly the same experience when he t r i e d to l e t young Wood Ducks hatch under a Mallard. I 29 decided to t ry experimenting on the call-note which i s happily well within the powers of the human voice to imitate. I took seven young Mallards and while they were drying under the e l e c t r i c heater I quacked to them my imitation of the mother Mallard's c a l l . As soon as they were able to walk the ducklings followed me quite as c l o s e l y and with quite the same react i o n a l i n t e n s i t y that they would have displayed toward th e i r r e a l mother. I regard i t as a confirmation of my preconceived opinion about the relevance of the c a l l note, that I could not cease from quacking f o r any consider-able period without promptly e l i c i t i n g the •lost-peeping' note i n the ducklings, the response given by a l l young anatides on having l o s t t h e i r mother. I t was only very much l a t e r , probably af t e r much conditioning to other characters inherent to my person, that they regarded me as their mother-companion even when I was s i l e n t . The l a s t piece of r e l a t i v e l y detailed reporting i n th i s a r t i c l e concerns the varying degrees of s p e c i f i c i t y of the postulated innate perceptory patterns occurring i n d i f f e r e n t species (pp. 2 5 3 - 2 5 ' + ) : Another example of a species with wide and l i t t l e s p e c i f i c innate perceptory patterns i s the S h e l l Parakeet (Melopsittacus undulatus). I raised i n i s o l a t i o n a young bird of t h i s species, which was taken out of the next of i t s parents at the age of about one week. I t was reared i n such a way as to expose i t to as l i t t l e stimulation from the keeper's side as possible. When fledged, i t was confined to a cage i n which a c e l l u l o i d b a l l was so attached that i t would swing to and f r o f o r a considerable time i f accidentally touched by the b i r d . My intention to transfer the sexual and s o c i a l reactions of t h i s b i r d to the very simple contrivance mentioned, succeeded beyond a l l expectations. Very soon the bird kept continually near the c e l l u l o i d b a l l , edged close up to i t before s e t t l i n g down to rest and began performing the actions of s o c i a l preening with the b a l l f o r an object. Notwithstanding the fa c t that the c e l l u l o i d b a l l had no feathers, the bird minutely went through a l l the movements of preening the short plumage of another bird's 30 head. One most i n t e r e s t i n g item i n the be-haviour of t h i s b i r d was that evidently he was treating the c e l l u l o i d b a l l as the head of a fellow-member of the species. A l l actions which he performed i n connection with i t were such as are normally directed toward the head of another parakeet. I f the b a l l was attached to the bars of the cage i n such a manner that the b i r d was at l i b e r t y to take any position r e l a t i v e to i t by holding onto the bars, he would always do so at such a l e v e l that h i s own head would be at exactly the same height as the c e l l u l o i d b a l l . When I attached i t c l o s e l y to a hori z o n t a l perch, so that i t was much lower than the head of the s i t t i n g b i r d , he would be at a loss what to do with hi s companion and looked 'embarrassed'. Thro-wing the b a l l loosely on the f l o o r of the cage e l i c i t e d the same response as the death of the only cage-mate does i n S h e l l Parakeets, namely, the b i r d f e l l absolutely s i l e n t and sat s t i l l i n the ' f r i g h t - a t t i t u d e ' with feathers depressed close to the elongated body. The only i n s t i n c -t i v e reaction not normally addressed to the head of a fellow-member of the species that I could observe i n t h i s i s o l a t e d b i r d , was the following: males i n courting a female excitedly run up and down a perch i n a quick sideways movement and f i n a l l y s i d l i n g up to her, they grip i n a p l a y f u l way at her lower back or at the base of her t a i l , using one foot and standing on the other. When my parakeet grew to mature age and began more seriously to court the c e l l u l o i d b a l l , he would execute exactly the same movements, but, as he was aiming them i n such a way that the b a l l repre-sented the female's head, h i s thrust-out claw would grip only vacancy below the c e l l u l o i d sphere dangling from the c e i l i n g of h i s cage. From these quotations i t w i l l r e a d i l y be seen to what extent Lorenz interprets and even suggests t h e o r e t i c a l explana-tions f o r the behaviour i n the midst of describing i t . Again, i n almost no instance i s there given s u f f i c i e n t l y precise d e t a i l of the developmental h i s t o r y of the animals i n the 3 1 observation or experiment such that i t can be adequately judged whether the evidence j u s t i f i e s the interpretations made. Such a s i t u a t i o n by no means implies that the interpretations are either incorrect or correct; t h i s i s pr e c i s e l y what cannot be decided without an examination of the missing d e t a i l s . Bear i n mind that these quotations are those which represent the most s p e c i f i c portions of the paper, and much of the r e s t of i t contains further suggestive but not demonstrative data, of an even more general nature. In defence of Lorenz's presentation i t can be said that he was at the time attempting to provide a t h e o r e t i c a l framework f o r the behaviour evidenced i n imprinting situations rather than simply to put on record the experiments and observations he had performed. However t h i s may be, the theory he presents i s very d e f i n i t e l y an ' i n s t i n c t 1 theory and since i t i s open to the c r i t i c i s m s (e.g., Lehrman's) already referre d to, more s p e c i f i c data are needed before an adequate causal explanation of the behaviour i n question can be reached. For a statement of the four most s i g n i f i c a n t character-i s t i c s of imprinting, see the e a r l i e r presentation of Lorenz's viewpoint (p. 10 above), to which matters further attention w i l l be given i n Chapter IV. Fabricius ( 1 9 5 0 ) i n reporting a number of h i s experiments confirmed much of the e a r l i e r data, and added to i t f u r t h e r : Stuffed dummies of adult female ducks of the same species as the ducklings, which remained motionless and s i l e n t produced no reaction i n the young. (He does not make clear 32 whether he means no following-reaction, or no reaction whatso-ever; since he speaks almost exclusively of the following-reaction i n h i s paper, t h i s could r e f e r to either of these two p o s s i b i l i t i e s . Later i n t h i s thesis i t w i l l be suggested that many changes i n behaviour other than following warrant i n c l u s i o n under t h i s heading) When these dummies were drawn forward along the water, they e l i c i t e d either escape behaviour or the ducklings paid no attention to them. The eleven ducklings used here were a l l of the same species, and were newly-hatched. In another part of the i n v e s t i g a t i o n , seventeen newly-hatched ducklings were presented with somewhat older ducklings of species other than th e i r own; ten of the seventeen crept to the other species and followed, i n spite of being harassed and nipped v i o l e n t l y . Some of the observations to be reported here confirm t h i s ; i t i s amazing to the observer how much punish-ment the newly-hatched birds w i l l take, and s t i l l approach the older b i r d . Fabricius reports that newly-hatched ducklings paid no attention to a human s i t t i n g motionless and quiet, but that they ran to a moving hand and arm, and followed i f the human walked away. He concludes that shape i s not important i n e l i c i t i n g following, but "the most e f f e c t i v e o p t i c a l stimulus must be any quality of movement, c h a r a c t e r i s t i c of l i v i n g vertebrates, but not occurring i n a swimming model drawn f o r -wards along the surface of the water." There i s much evidence, however, that the motion need not be as s p e c i f i c as t h i s , 33 indeed, objects on pulleys, moving hides (with the legs of the person inside hidden), and so f o r t h , have a l l been shown to e l i c i t following (see, f o r example,Hinde, Thorpe, and Vince, 1956). Ramsay and Hess (195*+) report that ducklings respond more r e a d i l y to a model of the male of the species than to a box, and ilaynes (1956) found that chicks prefer a red cylinder to a green cube. I t i s not clear whether form or colour i s the more important f a c t o r , but both these findings are i n contradiction to the above conclusion. I t i s worth noting that Hess and Gogel (195*0 found that chicks prefer l i g h t , desaturated colours ( i n a non-imprinting s i t u a t i o n , at l e a s t ) . The question requires systematic i n v e s t i g a t i o n before any conclusion can be reached. That even the d i r e c t i o n of the l i g h t i n g may influence the matter i s suggested by Hess 1(1950) work. J u l i a n Huxley sums up the present state of knowledge by h i s comment ( i n the recorded discussion of Hess 1 1956-57 paper): " . . . t h i s , I think, i s one of the strange things about i m p r i n t i n g — t h a t the s p e c i f i c i t y of the sign stimulus, so s t r i k i n g i n many animal reactions, i s l a r g e l y , although not e n t i r e l y , abolished." Although the quiet, motionless human evoked no approach behaviour from the ducklings, they did show t h i s i f the human c a l l e d "Kom, Kom, Kom," etc. Further, t h i s auditory stimulus, when the ducklings were placed i n an opaque-walled box without a s p e c i f i c v i s u a l stimulus, lead to a change i n the vocalization,of the birds from d i s t r e s s c a l l s to pleasure notes; the birds also crept i n the d i r e c t i o n of the sound-source. The "swimming" model mentioned above was approached by the ducklings i f i t was accompanied by the sounds, whereas they paid no attention to i t when the sound was absent. Fabricius notes that i t was sometimes necessary to repeat these sounds f o r some seconds before the birds would follow, "showing that the stimulus was successively accumulated u n t i l the l e v e l of reaction was reached." Although t h i s may be thought of as a plausible explanation of the delay i n these cases, one wonders whether the ducklings did not sometimes require a second or two to locate the source of the sound before they could move i n that d i r e c t i o n . Also, why should some birds need the stimulus to be "successively accumulated" while others, apparently, followed at once? F i n a l l y i t should be noted that such an int e r p r e t a t i o n would be d i f f i c u l t to t e s t — e s p e c i a l l y i n view of the f a c t that i t operates i n some birds but not i n others; what would be the nature of the prediction i n a given i n s t a n c e — t h a t i t would operate, or that i t would not? Neither r e s u l t would refute the suggested explanation. In the cases where the ducklings were following the moving human, following "was always better" when he c a l l e d as well as moved. This i s interpreted as an example of 'hetero-geneous stimulus summation', following Tinbergen ( 1 9^ 8 ) . With regard to the sensitive period during which imprinting i s possible, F a b r i c i u s found that, with birds i s o l a t e d i n the incubators f o r various periods a f t e r hatching, 9 the greatest reaction, i n the case of tufted ducks, occurred 35 when they were l e s s than 12 hours old, decreasing r a p i d l y with increased age (of f i r s t exposure). When the f i r s t exposure was at 2*+ hours or older, no following was observed. With mallards, however, following could be e l i c i t e d when the exposure was delayed u n t i l up to 72 hours, with the same inverse r e l a t i o n -ship holding between age of i n i t i a l exposure and pr o b a b i l i t y of following. Other experimenters, using a number of d i f f e r e n t species, found differences i n the c r i t i c a l period ranging from up to or about 8 hours of age [ i n the case of Peking ducks, (Moltz, i 9 6 0 , c i t i n g Moltz and Rosenblum, unpublished), and i n the case of coots, (Alley and Boyd, 1950)3, to s i x days of age [ i n chicks O J a y n e s , 1957), and i n coots (Hinde, Thorpe, and Vince, 1956)]. With these older ages, however, i t i s more the case that t h i s appears to be the outside limi t , of the period during which following can be e l i c i t e d , rather than the optimal period, which, i n most species investigated, seems to be during the f i r s t day, e s p e c i a l l y at around 16 hours of age (Ramsay and Hess, 195^; Moltz, i 9 6 0 , c i t i n g Moltz and Rosenblum, unpublished; Jaynes, 1957). I t appears to be the case that, both before and after an approximate c r i t i c a l period f o r a given species, the percentage of birds following, or the ease with which the following i s evoked, or the percen-tage of correct choices i n a subsequent test involving the fam i l i a r model and an unfamiliar female decoy (Ramsay and Hess, 195*0, declines. Fabricius (OP. c i t . ) notes that the e f f e c t of a v i s u a l stimulus decreases more r a p i d l y than that of an 3 6 auditory one, and the two together e l i c i t better following i n older ducks than a v i s u a l stimulus alone--BUT an auditory one alone released the reaction i n s t i l l older ducklings. This l a s t f i n d i n g , which appears to contradict any notions of "heterogeneous stimulus summation," i s explained as follows: a v i s u a l stimulus alone w i l l sometimes e l i c i t escape reactions, instead of following, i f the birds are at l e a s t s i x hours old, whereas the p a r t i c u l a r auditory stimulus used, ("Kom, Kom," etc.), would-never give r i s e to escape reactions. Although Fabricius does not go into t h i s further, he appears to mean that the auditory stimulus could be given an a r b i t r a r y r a t i n g f o r effectiveness as +2, and the v i s u a l stimulus would be rated ambivalently f o r older ducklings as + 1 and - 1 . Suppose then that, f o r whatever reason, the v i s u a l stimulus, on a given occasion, were acting i n i t s negative capacity, and both sti m u l i were presented together to a duckling over 6 hours of age; t h i s would r e s u l t i n a net effectiveness of + 1 ( i . e . , +2-1) . Now, although, i f the v i s u a l stimulus were functioning p o s i t i v e l y on t h i s occasion, the effectiveness would be + 3 , which i s greater than the effectiveness of the auditory stimulus alone ( = +2 ), and which i s presumably the case with "hetero-geneous stimulus summation," as the age of the duckling at the time of the exposure i s allowed to increase, the p r o b a b i l i t y that the v i s u a l stimulus w i l l e l i c i t the negative (escape) reaction quickly increases, with the r e s u l t that i n the majority of cases, the two stimuli together w i l l have an effectiveness of 3 7 +1 at best (since the v i s u a l stimulus by now i s becoming more negative than before), whereas the auditory stimulus remains with an effectiveness of + 2 . These ratings are purely hypothetical, of course, but t h i s analysis seems to be the sort of thing implied by Fa b r i c i u s . He states that, i n some cases, where the v i s u a l stimulus was presented alone, and had given r i s e to escape behaviour, i f the experimenter began c a l l i n g "Kom", the b i r d would stop, and might, i f the auditory stimulus were continued, turn back and follow. This would f i t the suggested analysis. With regard to the i r r e v e r s i b i l i t y of the response, Fabricius reports that ducklings who were imprinted to a human would not follow other ducks, but he notes that, i n some cases, "a kind of incomplete imprinting occurred." The young ducks would be following the human, "but every sudden or r a p i d movement released escape reactions, i n them." This occurred e s p e c i a l l y with those birds who had remained i s o l a t e d i n the incubator f o r a long time. As already noted, h i s c r i t e r i o n of imprinting seems to involve only following behaviour. This w i l l be seriously questioned i n a l a t e r chapter, i n discussing the observations to be reported, but i t may be noted that the phrase "a kind of incomplete imprinting" loses much of i t s meaning i f the behaviour referr e d t o — o t h e r than the following--i s part of a normally occurring but l e s s conspicuous, and therefore apparently l e s s relevant, pattern. To anticipate f o r 38 a moment, the present writer found that i n the imprinting s i t u a t i o n the chicks showed an immense variety of behaviour, most of which was NOT a constituent part of the following. Indeed, the most c h a r a c t e r i s t i c "single item" of behaviour, insofar as t h i s phrase has meaning, was watching the target object. Even the following reaction i t s e l f varied tremendously i n form—most chicks preceded the object rather than followed i t , some stayed close to i t most of the time, while others would l e t i t get several feet ahead of them and then dash ha l f the length of the pen to i t , while others spent as much time walking or running along the walls of the pen as they did i n the immediate v i c i n i t y of the target object, although they were c l e a r l y orienting t h e i r o v e r a l l behaviour towards the object. This poses a problem f o r the d e f i n i t i o n of imprinting as a phenomenon—both "incomplete" and complete. Jaynes ( 1 9 5 6 ) also stresses that there i s more to the behaviour than simply following, although he bases most of h i s discussion on a c r i t e r i o n which involves only following. This depends, of course, on the d e f i n i t i o n of imprinting, and w i l l be returned to l a t e r . In h i s t h e o r e t i c a l discussion, Fabricius c l o s e l y follows Lorenz's i n t e r p r e t a t i o n , i n terms of innate perceptory patterns and innate releasing mechanisms (I.R.M.). Before leaving the discussion of the c r i t i c a l period, i t i s well to note that such a concept i s by no means unique to imprinting as a phenomenon or as a process. For example, Scott 3 9 and Marston ( 1 9 5 0 ) , and Williams and Scott ( 195*+) discussed c r i t i c a l periods f o r the development of s o c i a l behaviour i n dogs and mice respectively, while much the same sort of concept features i n psychoanalytic theory. Scott and Marston suggest that the c r i t i c a l period hypothesis may reconcile many of the c o n f l i c t i n g r e s u l t s of experiments with i n f a n t s , f i n d i n g , as they do, that the e f f e c t s of early experiences, e s p e c i a l l y traumatic ones, are f a r more important during c r i t i c a l periods than at other times. With regard to dogs, they conclude that the period from about 3 1 / 2 weeks of age, when the puppy leaves the nest and meets other i n d i v i d u a l s , u n t i l eight to ten weeks, the time of weaning, i s the most important one i n the development of s o c i a l behaviour. The paper by A l l e y and Boyd ( 1 9 5 0 ) i s important mainly i n attempting to r e l a t e imprinting and other forms of early maturation and learning to species and i n d i v i d u a l recognition. Working with coots, they concluded that the reactions of the young were controlled by ' r e l e a s e r s 1 , i n p a r t i c u l a r releasers of following, and alarm, reactions. In the period up to about 8 hours of age, young coots w i l l follow humans, accept food from them, and respond to c a l l s made by them. By the second day, however, t h i s behaviour disappears, except i n the case of hand-reared young. At f i r s t the young w i l l follow and beg from any adult coot, but by about eight to eleven days they have learned to avoid adult coots i n an attitude of attack. This i s ho very much to the advantage of the young, since adult coots w i l l not tolerate them unless the adults happen to have young themselves which are both similar to the intruders and l e s s than two weeks old. The young appear to recognize the adults i n d i v i d u a l l y ( i . e . , over and above species recognition) by about three weeks. The basis of such recognition i s probably mainly i f not e n t i r e l y v i s u a l (including the recognition of behavioural c h a r a c t e r i s t i c s ) , since i t i s doubtful whether birds have any olfactory sensations, as olfactory s t i m u l i have not heen e f f e c t i v e as conditioned s t i m u l i i n conditioning experiments (Walter, 1 9 ^ 3 , c i t e d by Thorpe, 1 9 5 1 ) . In t h i s paper Thorpe, discussing the learning a b i l i t i e s of birds, re f e r s to Imprinting as an "innate d i s p o s i t i o n to learn". He follows Lorenz i n maintaining that patterned stimuli i n the environment serve as the key to unlock i n s t i n c t i v e behaviour, and r e l a t e s imprinting to the a c q u i s i t i o n of t e r r i t o r y and song. Ramsay ( 1 9 5 1 ) i s concerned to esta b l i s h the sensory factors that are involved i n e l i c i t i n g the following reaction and i n f a m i l i a l recognition i n domestic birds. He finds that such birds respond to vocal cues, (marked) differences i n si z e , form, and extreme differences i n colours (shades and t i n t s being i n e f f e c t i v e ) . These f a c t o r s , he suggests, vary according to the species under consideration. I t i s important to note that he discounts behavioural t r a i t s , although many such t r a i t s , being stereotyped and spe c i e s - s p e c i f i c , would be expected to function i n species recognition. This seems to be part of what Lorenz (1937) meant when he said, i n one of the passages quoted e a r l i e r , "The parent-child r e l a t i o n s i n t h i s a r t i f i c i a l family (adult Greylags and young Muscovies, P. J. D.) dissolved sooner than i s normal fo r any of the two species, owing to some hitches i n mutual understanding which occurred because the key and lock of the releasers and innate perceptory patterns of both species did not f i t . " With regard to the r e l a t i v e range between species, of objects which w i l l e l i c i t a following reaction, Ramsay found that incubator-hatched chicks and Canada Goose goslings would follow a small green box containing an alarm clock, the goslings and Muscovy-ducklings responded to a f o o t b a l l , but Mallards responded to neither of these. One wonders whether the greater s p e c i f i c i t y required i n the objects which Mallards w i l l follow i s linked with the r e l a t i v e l y long period i n which t h e i r following can be e l i c i t e d (Fabricius, 1950). Guhl and Ortman (1953), i n v e s t i -gating the reactions within groups of chickens to changes i n the appearance of one of the members of the group, found that i n d i v i d u a l birds react to a l t e r a t i o n s i n another bird's plumage, to intense colour changes i n the other b i r d , and to disguised features of the head and neck rather than of the r e s t of the body. The main c r i t e r i o n was whether the peck-order was disrupted when the altered b i r d was returned to the group. These findings are s i m i l a r to those of Ramsay ( 1 9 5 D , c i t e d e a r l i e r , but, i n contradiction to Ramsay, Guhl and Ortman found ^ 2 that deportment i s an important factor i n i n d i v i d u a l recognition. They conclude that some factors appear to be more s i g n i f i c a n t than others, but that no single factor i s the sole means of recognition, and they note that "Modification of features has to be abrupt and quite pronounced to cause a loss of recognition." Their experiments lack the control condition i n which a chicken i s removed, handled i n the same way that the chicken being altered i s handled, (except that no a l t e r a t i o n i s made to i t ) , and returned to the same group. This may or may not be important, but i t i s worthy of mention that they report that a chicken (unaltered i n plumage, etc.) shows a change of deportment when placed i n a strange group of chickens. Since these investigators found that a change of deportment does influence recognition, a report on the behaviour of the control chicken, and on i t s reception by the others i n i t s own group, might a i d i n deter-mining the relevant factors i n i n d i v i d u a l recognition. C o l l i a s ( 1 9 5 2 ) i n discussing the development of s o c i a l behaviour i n birds, maintains (p. 1 5 5 ) * S o c i a l development i s part of the development of behaviour i n general, and as such may be traced back through phy s i o l o g i c a l and chemical l e v e l s of organization to genetic f a c t o r s . What genes determine i n t h i s i n d i r e c t fashion i s the tendency to respond to more or les s s p e c i f i c s o c i a l s i t u a -tions; and the i n t e r a c t i o n between d i f f e r e n t l e v e l s leads to s o c i a l development. This means that physiological changes ( i n the secretion of hormones, f o r example) i n t e r a c t with s o c i a l situations as ^ 3 variables i n behaviour. He describes the development of behaviour by means of an embryological model ( p l a s t i c i t y , induction, e t c . ) , and s o c i a l patterning by means of a model of neural a c t i v i t y . In l i n e with t h i s p o s i t i o n , he states: "The basis f o r s o c i a l reactions i s l a r g e l y developed by the embryo before hatching takes place." Trends i n the s o c i a l i z a -tion of the young b i r d a f t e r hatching are summarized as follows: ( 1 ) Relative i n a c t i v i t y (some "spontaneous" or endo-geneous a c t i v i t y ) . (2) Generalized s o c i a l responses which become "strengthened, f i x a t e d , directed, and spec i f i e d by s o c i a l experience." ( 3 ) A period of increasing s o c i a l INDEPENDENCE, leading to the break-up of the family unit. (*f) Reintegration into new groups, f o r example, a grouping based on the establishment of a dominance hierarchy. Such groups are influenced by the balance of cooperative and competitive tendencies i n the birds, and are f a c i l i t a t e d by example and leadership. This precedes s o c i a l i z a t i o n , as parents within a new family group. A paper by Nice ( 1 9 5 3 ) records some of her experiences i n imprinting twelve ducklings of f i v e d i f f e r e n t species. She used the same technique as did Fab r i c i u s , namely moving her arm around near the ducklings, or walking away from them, c a l l i n g i n both cases, "Kom, Kom, Kom," etc. and her findings agree with those of Fabricius and Lorenz c i t e d above. One conclusion i s that the e a r l i e r the exposure and the more heterogeneous the stimulation, the more r e a d i l y i s imprinting effected. Since many references to s p e c i f i c types of c a l l are found i n the l i t e r a t u r e , a paper by C o l l i a s and Joos ( 1 9 5 3 ) warrants consideration i n t h i s context. These investigators made spectr©graphic records of the sounds made by the domestic fowl, and related these to the concurrent behaviour of the bir d . They c l a s s i f i e d the sounds as follows: A. Sounds made by chicks include d i s t r e s s c a l l s , pleasure notes, and fear t r i l l s . B. Sounds made by broody hens, that serve to a t t r a c t chicks, include clucking, food c a l l s , and the roosting c a l l . C. Warning signals include the alarm c a l l f o r a e r i a l preda-t o r s , the alarm c a l l f o r ground predators, the al e r t i n g c a l l of a broody hen, fear squawks of a hen held i n the hand, threat sounds by cocks, and the crowing of a rooster. They found that the d i s t r e s s c a l l s of chicks are composed of descending frequencies only, while pleasure notes contain ascending frequencies predominantly. Sounds that a t t r a c t chicks have the following common elements—repetitiveness or segmenta-t i o n ; brief,duration of the component notes; the presence of r e l a t i v e l y low frequencies. Warning notes, on the other hand, include such opposite features as long duration, l i t t l e segmentation or repetitiveness, and absence of low frequencies. k5 Experimental tests with a variety of sounds v e r i f i e d these conclusions; Thus when an observer speaks of d i s t r e s s c a l l s or pleasure notes, and so f o r t h , he i s probably on f a i r l y safe ground; the c l a s s i f i c a t i o n just referred to, however, was based on an analysis of spectrographic records which may be quite d i f f e r e n t from the judgements made during the course of observation, without the aid of such a machine. The spectro-graph provides a v i s u a l and permanent record, which can be analyzed at l e i s u r e afterwards, whereas i t i s often extremely d i f f i c u l t to judge whether the sounds heard include ascending frequencies, descending frequencies, segmentation and so fofcth. As w i l l be noted l a t e r , the present investigator found that, while extreme differences i n a chick's c a l l s could be d i s t i n -guished f a i r l y e a s i l y , most of them seemed to be at d i f f e r e n t points of a continuum, or of several continua of i n t e n s i t y ( e s p e c i a l l y ) , smoothness versus segmentation, and p i t c h . In t h e i r review (1951*-), Beach and J'aynes point out that the supposed i r r e v e r s i b i l i t y of imprinting may not occur f o r some time aft e r the i n i t i a l exposure to the target object. For instance, they c i t e Lorenz's report that Jackdaws, taken from their nest at fourteen days of age, were found to be imprinted to th e i r natural parents, but, a f t e r separation from adult jackdaws and continued association with humans from t h i s time on, the birds* p o s i t i v e s o c i a l responses could be s h i f t e d to humans. This s h i f t i n g i s possible apparently u n t i l about three weeks of age, after which time birds that have 1+6 been imprinted to adult birds can not be imprinted to humans, and vice-versa. I t might well be expected that, since humans have fed and cared f o r the birds, i n a number of cases, the subsequent attachment to humans might be due not so much to a reversal of imprinting.as to "ordinary" reinforcement-learning. This seems to be the case with the wild gosling captured, when between one and two weeks old, by Steven ( 1 9 5 5 ) . The gosling was placed i n a cage on meadow-land, by humans. I t was moved to fresh pasture each day, by humans. Water was provided, when required, by humans. They were humans, too, who l e t i t out to graze and who stood near i t while i t was eating. I t i s not surprising that i t soon l o s t i t s fear of the humans at the camp, and even the f a c t that i t d i d not respond well to v i s i t o r s to the camp requires no i n t e r p r e t a t i o n i n terms of "re-imprinting." This, Steven claims, occurred on the s i x t h day a f t e r capture, "as a revolution i n the bird's behaviour", although he does acknowledge that from day four the b i r d showed some positive responses towards humans, to whom i t had o r i g i n a l l y shown fear responses. He suggests that imprinting and habituation are linked—when the f l e e i n g tendency i s lowered s u f f i c i e n t l y , imprinting becomes possible. This would seem to imply that, so long as an experimenter could habituate a b i r d to fear-provoking moving objects, he could bring about transferences of imprinting i n d e f i n i t e l y . In the case reported by Steven, however, any such i n t e r p r e t a t i o n seems unwarranted, since, f i r s t l y , reinforcement-learning must have h7 played a major r&Le, and, secondly, the behaviour of the b i r d , subsequent to these experiences, towards the o r i g i n a l objects of i t s imprinting, i t s natural parents, was not observed. Since Lorenz's jackdaws would not s h i f t t h e i r p o s i t i v e responses to humans i f the birds were older than two weeks, however, reinforcement-learning cannot be the only f a c t o r operating i n these cases. The experimental procedure which would allow a more decisive answer to be reached would involve allowing the newly-hatched b i r d to follow a human for some time, and then placing i t i n the presence of some non-human moving target-object f o r several t r i a l s . The o r i g i n a l observation, on which Lorenz based h i s statement that imprinting i s i r r e v e r -s i b l e , was made under conditions such as these (see page above). During the week i n which the young Greylag was is o l a t e d from i t s kind, and i n contact with humans only, i t was probably fed and cared f o r by humans (Lorenz i s not e x p l i c i t here), therefore the same procedure, but with s t r i c t e r controls might w e l l be worth adopting. In t h i s case, suppose t h a t — apart from any imp r i n t i n g — t h e b i r d received food, water, warmth, and possibly some form of handling which might have been p o s i t i v e l y r e i n f o r c i n g , from the human(s) during the f i r s t week, and then, when placed with the Turkey hen, received warmth only from t h i s b i r d (which, i n any case, i t needed le s s than before); would i t then be surprising that the young Greylag "preferred" humans to a Turkey hen? I t follows from t h i s that imprinting has been shown to be neither r e v e r s i b l e nor kQ irreversible. In fact, l i t t l e , i f anything can be said about imprinting in a case such as this. It will be recalled that Fabricius ( 1 9 5 0 ) observed that, when ducklings were imprinted to humans, they would not follow other ducks, but, again, i t is not certain that the birds received none of the conventional reinforcers from the humans. It is interesting to note that Nice ( 1 9 5 3 ) found that the ducklings which were imprinted to her did not eat properly unless kept with other ducklings who were efficient eaters. This seems to be a case in which an attempt was made to avoid reinforcing the attachment to a human, but, unfortunately, no data on reversibility were reported. Nice goes so far as to state that, in these circumstances, unless the birds can either be kept with efficient eaters or fed by humans, they will die. This i s , regrettably, the reverse of the control condition necessary. Beach and Jaynes (OP. cj.t.) also report that in some cases not a l l subjects, in an imprinting situation, follow, and some of a group, in which most of the birds react positively, are not imprinted (see especially Jaynes, 1 9 5 6 , 1 9 5 7 ) . This is one of the main findings of the present study, and i t is surprising that scant mention of the matter has been made in the literature. These authors also refer to a number of studies of mammalian imprinting (Murie, 1 9 M + ; Scott, 1 9 ^ 5 ) » but, again, the conditions (e.g., being bottle-fed by humans) point to an interpretation in terms of reinforcement-learning rather ^ 9 than of imprinting. Gray ( 1 9 5 8 ) takes the smiling of human infants to correspond to the following of newly-hatched birds. He finds evidence for a critical period lasting from six weeks (when the smile is f i r s t given to a nodding face) until six months (the onset of fear reactions), and cites the work of Bowlby (e.g., 1 9 5 1 , 1 9 5 3 ) , in particular, in support of his argument. Even i f Bowlby's evidence were not, to a large extent, anecdotal and loosely controlled, his interpretation of the causal relationship between parental loss at a certain age and subsequent adolescent emotional and behavioural disturbance is open to serious question. In any case, i t is notoriously certain that the almost continuous positive reinforce-ment extended to the human infant in the f i r s t six months of its l i f e confounds any interpretation in terms of imprinting. Ramsay and Hess ( 1 9 5 * 0 , in addition to the findings cited earlier in connection with the c r i t i c a l period and with form preferences, contribute some further data on the relation of fear to imprinting and on the nature of the relevant stimulus properties. Fourteen ducklings were exposed to the imprinting situation at between 2 1 and 2k hours of age. Of these fourteen, eleven showed strong fear responses. They point out that It seems significant that the only ducklings that showed any appreciable imprinting in the 2 1 -2k hour group were the same individuals that showed no alarm. 5o They found that, while noise was necessary to e l i c i t approach to a stationary model, the ducklings showed no clear-cut preference between three types of noise-recorded duck quack, spoken simulated quack, and recorded human "goek". Motionless calling models were effective as target-objects, as evidenced on subsequent tests. They add a comparative finding that Cochin Bantams showed poorer imprinting than, but about the same critical period (13-16 hrs.) as the ducklings. The bantams preferred the recorded cluck of the mother hen to the human recorded "gock", which might account for their low imprinting scores, since the cluck of the mother was not used with the models presented to them as target-objects. Evidence apparently contradicting that of Fabricius, referred to earlier, on imprinting to sound alone, was that three ducklings, to whom a recorded "gock" sound was played from hatching until they were 2h hours old, showed no evidence of imprinting to that sound. Using somewhat different conditions, Fabricius found that ducklings stopped giving distress calls in response to his continued calling "Kom", (and other monosyllables), and that they crept towards the sound source. Some further evidence on this point will be presented in Chapter III. Hinde (1955) uses imprinting as a descriptive example "of the ways in which behaviour, which has developed without the intervention of 'learning1 processes, may be subsequently modified by them." In treating imprinting as "not fundamentally 51 d i f f e r e n t from other forms of learning," he suggests that i t s mode of action i s to a f f e c t the s t i m u l i which e l i c i t the behaviour observed i n a given s i t u a t i o n . The reports (e.g., Lorenz 1935, 1937), that later-maturing behaviour may be directed towards the o r i g i n a l target-object, are c i t e d , but Hinde adds the important note that, i n the case of subsequent responses directed towards man, i n p a r t i c u l a r , t h i s may well be due to the operation of other learning processes. The f a c t that following the moving object may be rewarding i n i t s e l f i s noted by Hinde—a suggestion which i s c e r t a i n l y i n accord with what i s observed, but one which requires a serious r e v i s i o n of the t r a d i t i o n a l notions of reinforcement, as discussed e a r l i e r i n t h i s chapter. Verplanck (1955) introduces a s l i g h t l y d i f f e r e n t i n t e r p r e t a t i o n of imprinting: Imprinting i s regarded as simple S-R learning occurring under somewhat special conditions. An i n i t i a l weak tendency to follow moving objects of s p e c i f i a b l e size i s strengthened by r e p e t i t i o n of the following behaviour. This following behaviour becomes r e s t r i c t e d to a p a r t i c u l a r c l a s s of object by a later-appearing s p e c i e s — s p e c i f i c tendency to fear and to escape from objects of the same general class as that which i n i t i a l l y excited following. Only the class of objects that the animal has had extensive practice i n following retains the property of exciting following; the animal remains "tame" with respect to i t . This sparing i s a case of the transfer phenomenon c a l l e d proactive i n h i b i -t i o n i n other contexts. When adult behaviour appears, proactive i n h i b i t i o n should lead to interference (by p e r s i s t i n g fear and f l i g h t components of 5 2 behaviour) with response to those objects that had NOT been followed prior to the appearance of the fear and f l i g h t behaviour i n the animal's early days. The p a r a l l e l drawn, however, i s not e n t i r e l y unambiguous. Proactive i n h i b i t i o n normally arises i n situations i n which subjects are required to learn a l i s t of items, and then to learn a second l i s t . The ease with which they learn t h i s second l i s t i s compared with that of a control group of subjects who learn only the second l i s t . I f t h e i r score i s s i g n i f i c a n t l y lower than that of the control group, t h i s i s interpreted, c e t e r i s paribus, as proactive i n h i b i t i o n — i . e . , the process of learning the f i r s t l i s t i s said to upset the process of learning the second one. I f the experimental group has a score, f o r the second l i s t , which i s s i g n i f i c a n t l y higher than the control group's score, t h i s i s c a l l e d proactive f a c i l i t a t i o n . The corresponding experimental group i n Ver-planck's discussion i s the group of birds who have been imprinted. The control group i s made up of any other birds of the same species, reared i n the same fashion, but having experienced no moving objects of the relevant c l a s s , prior to the development of the fear and escape tendencies. Each group at the adult stage would be confronted with the objects which the imprinted group (only) had followed p r i o r to the appearance of fear and f l i g h t behaviour i n t h e i r early days. Now, Verplanek maintains, "proactive i n h i b i t i o n should lead to interference (by p e r s i s t i n g fear and f l i g h t components of 53 behaviour)" towards these objects now presented, i n the case of the control group, while the experimental group should exhibit t h e i r usual (following) behaviour towards the objects. In other words the "score" of the experimental group would be "higher" than that of the control group; t h i s i s proactive f a c i l i t a t i o n not proactive i n h i b i t i o n . (A "higher score" means that they did not fear and f l e e from the objects presented.) A more serious d i f f i c u l t y l i e s i n the f a c t that i t i s the control group which appears to be affected by proactive i n h i b i t i o n i n t h i s c a s e — t he group which did NOT undergo the i n i t i a l learning; i t i s d i f f i c u l t to see how the p a r a l l e l with proactive i n h i b i t i o n holds. Fabricius notes, i n 1955, that following, avoidance, or aggression might be shown by young Mallards towards simple moving models (mostly boxes and balloons) i n a runway—a finding which agrees i n a l l respects with those to be reported i n Chapter I I I . He states that any model could e l i c i t a l l these responses. The t sensitive period was not sharply l i m i t e d , but the highest proportion of followers was found among birds f o r whom the i n i t i a l presentation was made when they were between twenty-five and f i f t y hours of age. This does not e n t i r e l y agree with h i s e a r l i e r report (195D on Mallards wherein he f i n d s that the p r o b a b i l i t y of obtaining the following was inversely r e l a t e d to the age at which the i n i t i a l exposure occurred, but i t does confirm that Mallards have a 9+ longer sensitive period than do, f o r example, tufted dueks. He notes that older ducklings tended to show i n i t i a l avoidance rather than following, and that: Ducklings f a i l i n g to follow the models also tended to avoid other ducklings on f i r s t meeting them. (See also Melzack et a l . , 1 9 5 9 , pp. 6 9 6 - 6 9 7 ) : :^v-;-The r i g i d i t y of the following, once established, was also i n v e s t i g a t e d — t h e i n i t i a l exposure was to a balloon and subsequent ones were to a box or to the balloon ( i n some cases the i n i t i a l object was a box). The r e s u l t was: "While several followed the strange model i n addition to the f a m i l i a r one, i n a l l cases the response to the former was l e s s intense." This i s confirmed by Jaynes ( 1 9 5 6 ) with respect to young chickens, and using red cylinders and green cubes. Fabri c i u s also mentions that some model-followers developed a tendency to follow men afte r several weeks; t h i s s i t u a t i o n was discussed e a r l i e r . Moltz ( i 9 6 0 ) points out that the supposed i r r e v e r s i -b i l i t y of imprinting may mean either (or both) that once a cer t a i n type of object has been followed, objects d i s s i m i l a r to i t w i l l not be followed ( i . e . , i r r e v e r s i b l e = no stimulus generalization possible), or that once an object has been followed, i t w i l l continue to be followed throughout the animal's l i f e ( i . e . , i r r e v e r s i b l e = stable). Both Fabricius and Jaynes (OP. c i t . ) were inv e s t i g a t i n g stimulus generalization; the 55 question of the s t a b i l i t y of the behaviour has been raised e a r l i e r i n connection with Lorenz's early work, and i t w i l l be returned to i n a moment. The abstract of Thorpe's paper (1955) r e i t e r a t e s the contention that imprinting i s not a d i s t i n c t form of learning, but that i t has somewhat sp e c i a l c h a r a c t e r i s t i c s , including that of being supra-individual learning. Its function seems to be to b u i l d r a p i d l y upon and so complete the adjustment of the i n -nate releasing mechanisms of c e r t a i n s o c i a l behaviour patterns which are of c r u c i a l importance i n the l i f e h i s t o r y of the organism. This i s e s s e n t i a l l y the same as Lorenz's l a t e r p o s i t i o n (195*+). With reference to the question of i r r e v e r s i b i l i t y , Thorpe c r i t i c i z e s many studies on the grounds that the objects ( e s p e c i a l l y i f human) appear to have become "contaminated" with reinforcement ( i n Moltz fs words), and that a clear-cut i n t e r p r e t a t i o n of the r e s u l t s becomes impossible. Hess (1956-57) states that imprinting i s the name given to the presumed f a c t that "early s o c i a l contacts determine adult s o c i a l behaviour." Although c h i e f l y concerned with the e f f e c t s of meprobamate on Imprinting, he adds to our knowledge of the matter i n a number of other respects. While most other experiments have been performed i n an open-field s i t u a t i o n (e.g., Lorenz, 1937)> or using a straight runway and pulleys (e.g., Jaynes, 1956)—although Hinde, Thorpe and Vinee (1956) 56 used a combination of these—Hess made use of a circular runway, five feet in diameter, twelve inches wide, and 12 1/2 feet in circumference at the centre. The target-objects were suspended from an elevated arm radiating from the centre of the apparatus, and were fitted internally with a loudspeaker and a heating element. The birds (Mallards) f e l l through a trap-door in the runway to be'returned to their boxes. It is worth noting that this apparatus, but even more so the straight runway type, is set up in such a way that the bird is more free to move in a longitudinal direction, or around the circle in the latter case, than in a transverse direction (equivalent to moving towards or away from the centre of the circular apparatus). Its move-ment would be blocked sooner by the walls of the runway, i f i t moved transversely than i f i t moved along the apparatus. On a chance basis alone, therefore, one might expect more movement to occur along the runway, and, since this is also the direction in which the target-object moves, this effect should be taken into account in discussing the strength of the bird's following. The optimal type of apparatus would seem to be a walled circular area, with no equipment or walls inside the outer boundary. This would enable the bird to move equally freely in a l l directions within the circle. Pulleys, etc. would have to be supported from above, or the target-pbject moved by means of battery-supplied power, clockwork, or remote control. 5 7 Hess used an imprinting period which was "usually less than one hour"; this is considerably longer than the usual period, which varies from ten to thirty minutes. His test for imprinting involved a choice between the familiar and a strange model under four successive conditions of movement and/or sound by one or both of the models. The findings were that the optional period for imprinting is around the sixteenth hour after hatching; distance travelled, rather than length of exposure, is a crucial factor (in this part of the experiment, exposure time was held constant within each of three groups at 2 , 1 0 , and 3 0 minutes respectively); and that the drugs used on the birds had the following effects: ( 1 ) Meprobamate "reduces the fear or emotional behaviour (and) makes imprinting almost impossible. It does not, however, interfere with the effects of imprinting." By "almost impossible", Hess means during the normal c r i t i c a l period, as he points out in his summary. ( 2 ) "Animals given a standard dose of meprobamate at 2k hours cannot be imprinted at 2 6 hours, even though they do not show the fear and avoidance behaviour ordinarily exhibited at that age." This appears to support the notion of a species-specific cr i t i c a l period for imprinting, but i t does not support an interpretation to the effect that the critical period is ended by the development of fear and escape tendencies which give rise to behaviour incompatible with following (Hinde, Thorpe, land Vince, 1 9 5 6 ; Hinde, 1 9 5 5 ; 5 8 Hess, 1 9 5 9 ; Moltz, i 9 6 0 ) . ( 3 ) "Meprobamate appears to extend the c r i t i c a l age f o r imprin-t i n g . Animals given meprobamate at twelve hours can be imprinted f a i r l y successfully at 2k to 2 6 hours, when the e f f e c t of the drug has worn o f f . " Hess interprets t h i s as being due to a slowing e f f e c t of the drug on the metabolism of the animal. These animals, at 2k to 2 6 hours, were fu n c t i o n a l l y similar to untreated animals roughly 1 6 hours old, as i t were. (*+) Chlorpromazine, given at 2k hours and followed by imprinting at 2 5 hours ( i . e . , corresponding to the conditions of ( 2 ) above, but with a d i f f e r e n t drug), allowed imprinting to be effected at 2k to 2 6 hours. In inte r p r e t i n g t h i s r e s u l t , Hess refe r s to the e a r l i e r f i n d i n g that the strength of imprinting i s a function of the e f f o r t expended or of the distance t r a v e l l e d , and states: I t may be that, since meprobamate i s a muscle relaxant, these e f f e c t s of meprobamate cut into the muscular tension or other afferent consequences and thus n u l l i f y the effectiveness of the imprinting period. Since, under the same circumstances, we a t t a i n p e r f e c t l y good imprinting i n a l l cases with chlorpromazine, t h i s notion be-comes even more tenable. Weidmann ( 1 9 5 6 ) also reports r e s u l t s that do not support the suggestion that the c r i t i c a l period i s l i m i t e d because of developing fear and escape behaviour. He confirms that the stimulus situations which Fabricius ( 1 9 5 0 ) found to 5 9 e l i c i t following, are e f f e c t i v e , and also confirms the data on the c r i t i c a l period f o r Mallards, but he says: This period was not due s o l e l y to an increasing escape tendency i n h i b i t i n g the following: kO hours old ducklings though not frightened would not react any more when c a l l e d . He adds that: The underlying process ( i . e . , the process underlying imprinting, P.J.D.) takes a b r i e f time, and does not occur at the beginning and at the end of the sensitive period. Weidmann observes that the behaviour of imprinted and non-imprinted animals, i n the absence of the releasing s t i m u l i , i s very d i f f e r e n t . An imprinted duckling stops other a c t i v i t i e s and searches; the non-imprinted one shows no such appetitive behaviour, " i t has l o s t (or never gained) t h i s urge to be near a parent." That birds who have been following a target-object run around and/or stand with head up and moving about, and give loud d i s t r e s s c a l l s i f that object suddenly ceases to move when i t i s distant from them and i f they were not looking i n i t s d i r e c t i o n at the moment when i t stopped moving, w i l l be seen i n Chapter I I I . In t h i s context a study by C o l l i a s and C o l l i a s ( 1 9 5 6 ) on the behaviour--particularly the c a l l s — o f ducks and ducklings under natural conditions i s relevant. The two kinds of duck (surface-feeding and d i v i n g ) , were observed from bides from before the ducklings were hatched and f o r some 6 0 days afterwards. They note, inter alia, that there was a period of at least 1 8 hours before the mother duck and her young left the nest together. This quite prolonged period of association in the nest provided considerable opportunity for the mother and young to become conditioned to each other. When the mother left the nest (during this 1 8 hour period) abruptly, the young made no effort to follow her. The leaving of the nest by parent and young together was a gradual and drawn-out process in the case of the ducks with their nest over the water, but i t was relatively quick with the other species. When a duckling became separated from the rest of the brood, i t gave distress calls; when i t rejoined the brood i t gave contentment calls. The parent gave attraction calls more loudly and rapidly when the brood was actually leaving the next, and, these authors note, the young do not necessarily follow the parent as soon as she leaves the nest, even when she calls them (Gf. Fabricius, 1 9 5 0 , on "successive stimulus accumulation"). This attraction note of the moving parent, compared with the other calls of the species, was relatively soft and low pitched, and consisted of brief, rapidly repeated, monosyllables of low intensity, (Cf. Collias and Joos, 1 9 5 3 ) • With regard to the following response, Collias and Collias conclude that both sound and movement are important factors in i t s elicitation, and that the best time for its 6 1 development i s on the f i r s t day (see C o l l i a s 1 9 5 2 , F a b r i c i u s 1 9 5 0 ) . Below f i v e hours of age, the ducklings' legs appear to be too weak f o r following to be accomplished, and ducks older than 2k hours show a marked fear response to any large approach-ing object, hence these authors agree with the previously mentioned suggestion that these factors l i m i t the duration of the c r i t i c a l period (see also Hess, 1 9 5 9 ) . An observation of some i n t e r e s t i s that two ducklings, which were three days old and had not been "trained to follow," followed a s i l e n t moving human i f they were placed with two other ducklings that had been trained to follow. I t i s presumed that the two "naive" ducklings had not been i n the company of other ducklings prior to t h i s occasion, since, i f t h i s had been the case, the naive ducklings might be said to have been imprinted to the others, who, i n turn, were imprinted to humans, which would account f o r the observed behaviour. C o l l i a s ( 1 9 5 7 ) describes and analyzes the process of s o c i a l i z a t i o n i n sheep and goats, which shows some s i m i l a r i t i e s to imprinting. He reports on several p a r t u r i t i o n s , and the f i r s t few hours thereafter, i n p a r t i c u l a r , i n terms of the mother-child r e l a t i o n s h i p s , bringing out the f a c t that much of the behaviour i s of a r e c i p r o c a l n a t u r e — f o r example, a parent w i l l answer the c r i e s of an infant with i t s own c r i e s , and w i l l move towards i t . He finds that a lamb or kid , removed from i t s mother at b i r t h , and kept away from her f o r two hours or more, w i l l probably be 6 2 rejected when i t is returned to her. (Cf. Alley and Boyd, 1 9 5 0 . ) (MRejection" means that the mother withdraws from the neonate's nursing attempts, and butts i t away when i t approaches.) Collias believes that ...the probable reasons for the crit i c a l importance of the fi r s t few hours post-partum in the establishment of the social bond between mother and young in sheep and goats are: ( 1 ) facilitation by attraction of the mother to the fetal membranes and birth fluid, as well as to the young one itself, ( 2 ) maternal drive is apparently highest at, or near, the time of parturition, and ( 3 ) a very rapid learning process results in early fixation of the female on her parti-cular young. Some aspects of later social development are also described, including the reduction in the frequency of nursing, the appearance of aggressive and sexual behaviour, and the persisting companionship in mature l i f e . This is generally comparable to the same author's 1 9 5 2 paper (see above) in which he discussed the development of socialization in birds. The importance of an organism's early social and perceptual experience for its subsequent social and other adaptive behaviour is emphasized in a paper by Melzack and Thompson ( 1 9 5 6 ) . It will be recalled that the work of Scott and Marston ( 1 9 5 0 ) on periods critical for the development of normal, as opposed to mal-adjustive, social behaviour in dogs, was carried out with normal, variable, and unrestricted conditions of visual and social stimulation; this study by Melzack and 6 3 Thompson involved the restriction, to a number of different degrees, of the dogs1 social and perceptual experience. Some dogs were reared freely as pets, while, at the other extreme, some were kept, in social isolation (from both other dogs and man) and with perceptual restriction, in cardboard-covered cages for between seven and ten months. At the end of this time a l l the dogs were given a series of tests of social behaviour: Tests for dominance showed that the restricted dogs were strikingly inept in a competitive situation, as compared with the high degree of dominance behaviour displayed by the normal controls. Similarly, the re-stricted dogs did not exhibit the sustained, well-oriented curiosity towards other dogs that was observed in the control dogs. The restricted dogs were unable to accept and reciprocate the friendly approaches of a •friendly man', or avoid physical contact with a 'bold man1 in the unexcited, well-organized manner typical of the normally reared dogs. The experimenters conclude: r Restriction of early social experience has a definite retarding effect on the emergence of normal, adult, social behaviour in dogs. Yery l i t t l e is known, as yet, of the internal aspect of such restrictions (e.g., the physiological differences which may be caused by such conditions, and which mediate—in part at least—the observed behaviour). These findings are, of course, meaningful in their own right without such complementary data. 6h The work of Hinde, Thorpe, and Vince ( 1 9 5 6 * , see also Hinde 1 9 5 5 ) has already been referred to in connection with the critical period and the development of incompatible escape tendencies; i t contains much important evidence on the possibil-ities of stimulus generalization. The experiments were performed using a large (2k yards by 6 1/2 yards) grassy area, with slotted fencing around i t . Objects could be moved along inside this area on a quiet or a noisy pulley. Sometimes a human served as the target-object, silent or calling as he walked about the area; on a number of occasions a man would walk with a hide over himself and material trailing from the bottom of the hide to the ground, so that no part of his body could be seen by the moorhens or coots used in the study. These authors found that several different objects elicited following, as long as they were in motion. Birds could be trained to follow different objects on successive runs. Birds trained on one model would generalize to others presented in the same circumstances through-out almost the entire period in which they would follow at a l l — this clearly repudiates the suggestion that imprinting is irreversible (e.g., Lorenz, 1 9 3 7 ) i f by this is meant 'no stimulus generalization possible' (see page 0 above). With massed trials, however, the following of a familiar model was maintained at a steady level, while that of an unfamiliar one declined irregularly. The suggestion that following may be self-reinforcing has been noted earlier in connection with this work, and i t is made use of in the hypothesized explanation of 65 t h i s f i n d i n g . They propose that following a f a m i l i a r object brings more reinforcement than following a strange one. Moor-hens were more l i k e l y to follow i f tested on the f i r s t day than i f tested subsequently, when they tended to f l e e ; these birds also showed a stronger response to the hide than did c o o t s — the authors suggest that t h i s i s due to the "shelter 1' character-i s t i c s of t h i s object. In addition to t h i s , Moorhens generalized to unfamiliar objects l e s s r e a d i l y than did coots, who were the better followers, whose day-to-day following scores remained steadier, and who were l e s s affected by changes i n the environ-ment. I t i s clear that, whatever causal explanation i s offered fo r imprinting, and whatever variables, hypothetical or other-wise, are invoked, there i s positive evidence that the c h a r a c t e r i s t i c s of the behaviour observed i n these situations does vary between species. The most systematic i n v e s t i g a t i o n of the various aspects of imprinting i s the series of experiments reported by Jaynes (1956, 1957, 1958(a), 1958(b)). The f i r s t of these papers reports studies on development and generalization. The target-object moved, on a pulley system, at a speed of one foot per second, i n a straight runway, with two 8-second pauses, and one 30-second pause,per minute, aft e r k seconds, 16 seconds, and 30 seconds, respectively; there was also a 2-minute pause a f t e r each 5-minute period. The subjects were chickens (New Hampshire Reds), taken from a hatchery at between one and two hours of age, 66 and housed c o l l e c t i v e l y . The measure employed was the time spent within one foot of the target-object. The distance followed eannot be calculated from t h i s measure plus the known speed of the object, since Jaynes notes that most of the scores accumulated during the pauses. An estimate of the chance score was obtained, which was taken into account i n the r e s u l t s . No sound was Used as part of the stimulus; the target-object was a red cylinder or a green cube, which moved two inches above the f l o o r ; each session lasted for h a l f an hour, before which the chicken remained i n the runway for one minute before the target-object began to move. The two-minute pauses were rest periods, and are additional to the t h i r t y minutes. The behaviour of the chicken i n the presence of the target-object included the following components: attention to the target-object; v o c a l i z a t i o n ( s a t i s f a c t i o n versus d i s t r e s s c a l l s ) ; approaching; and f o l l o w i n g — u s u a l l y i n that order. The general trend of the scores was upwards during each successive 5-minute period of the session (from around 60 seconds during the f i r s t 5 minutes, to IQk seconds during the l a s t 5 minutes). Very young birds showed poor locomotion, and only short periods of sustained attention. Jaynes points out that t h i s would account for t h e i r poorer scores. The tests were continued f o r four days. When the scores obtained during the l a s t 5-minute period of each day's session were compared, they were found to have r i s e n from about l * f l seconds to 2k2 seconds, f o r the green 6? cube, and from 12k to 215 seconds, f o r the red cylinder. Based on the TOTAL SCORE f o r each day, the green cube was followed to a s i g n i f i c a n t l y greater extent (p = 0.05) than was the red cylinder. By the fourth day, the following was consistent and vigorous: Whenever the object moved, the b i r d chased; when i t paused, the b i r d always stayed close, usually uttering contentment notes and pecking, as though feeding, at the f l o o r (no food present). Thus the behaviour, as measured i n t h i s way, improves on subsequent t r i a l s ; consistent following i s not observed at f i r s t , as has been implied, at l e a s t , i n most of the other reports referred to, but rather requires, as Jaynes suggests, the strengthening, through maturation and use, of the organs involved i n running. That these r e s u l t s depend upon t h i s p a r t i c u l a r measure i s c l e a r ; i t does not necessarily mean, however, that the e f f e c t of the moving stimulus was accumulating from day to day i n the sense that t h i s was the 'cause' of the improved performance. Since t h i s measure r e f l e c t s mainly the improved a b i l i t y of the b i r d to run, there i s no evidence that the i n i t i a l exposure was le s s e f f e c t i v e than were subsequent ones. In another experiment, the target-object was switched, on days three and four, during part of the 30-minute s e s s i o n s — the o r i g i n a l object was presented both before and afterwards during the same session. There was a s i g n i f i c a n t decrement 68 when the b i r d was following the 'wrong' object (p = 0.05), also, the decrement following the switch from the red cylinder to the green cube was s i g n i f i c a n t l y greater than the decrement following the switch i n the reverse d i r e c t i o n . This suggests that the red cylinder had the greater e f f e c t upon the b i r d than the green cube rwhich i s further implied by Jayne's note that two of the birds trained to the red cylinder f l e d from the green cube when thi s was presented—each time i t approached they f l e d along the walls of the a l l e y , uttering d i s t r e s s c a l l s . No f r i g h t of the new object (the red cylinder) was observed i n birds trained f i r s t to the green cube. This c o n f l i c t s s l i g h t l y with the e a r l i e r r e s u l t (that there was somewhat better following of the green cube),, unless following were conceived of as a positive function of anxiety (see Moltz, i960). Upper l i m i t s to t h i s would be necessary, however, as otherwise, the b i r d would show i t s fear of a moving object by remaining continually near i t J In a choice-discrimination t e s t , the birds always went to the object to which they had been imprinted. As the objects were motionless, and as the chickens took about h a l f a minute, a f t e r being released, to make the i r choice (even though they had been able to see the two objects f o r one minute before being released), t h i s confirms, as Jaynes notes, that motion i s of c r u c i a l importance as a c h a r a c t e r i s t i c of the target-object (see James, i960, on f l i c k e r and imprinting). Before they made their choice, and a f t e r being released, t h e i r behaviour included d i s t r e s s c a l l i n g , pecking, and "standing 69 about"—there was never an immediate rush to the object. The higher followers (group scores) took s i g n i f i c a n t l y less time than the others to make their choice. These r e s u l t s , l i k e those of Hinde, Thorpe, and Vince (1956), do not support the contention that imprinting i s i r r e v e r s i b l e i n the sense which implies that no generalization i s possible. They say nothing d i r e c t l y about the l a t e r s t a b i l i t y of the response with respect to the o r i g i n a l target-object--the other meaning of ' i r r e v e r -s i b l e '. In h i s 1957 paper, Jaynes reports on investigations of the c r i t i c a l period, which have some bearing also upon the problem of response s t a b i l i t y . The general method and procedures were the same as before. There was only one target-object (the green cube); the birds were i n i t i a l l y exposed at varying ages, at which time their response-strength was recorded; they were re-tested ten days l a t e r . The imprinting c r i t e r i o n was that the b i r d should follow f o r at l e a s t s i x t y seconds of the 5-minute period (the f i n a l period i n the 30-minute session). Below t h i s l e v e l the behaviour was attributable to chance f a c t o r s . As a control, two groups of seven birds were i n i t i a l l y exposed on the 12th and 13th day afte r hatching. Jaynes found that a higher percentage of younger birds reached the c r i t e r i o n . Fifty-four-hour old birds showed no following. As older birds were used, so the mean following 70 score improved (although le s s birds were reaching the c r i t e r i o n ) . On the "juvenile" re-exposures ( i . e . , ten days l a t e r ) , whereas 33% of the youngest group on the i n i t i a l exposure reached the c r i t e r i o n , only 33$ now did so. A similar decre-ment was found with the next group ( i . e . , birds i n i t i a l l y exposed at a s l i g h t l y older age). In a l l groups whose i n i t i a l exposure was at or a f t e r 2k hours, the re-exposure score f o r incidence was improved. For example, although h a l f the subjects, i n i t i a l l y exposed on the second day of l i f e , showed no evidence of imprinting at that time, 10 days l a t e r a l l but one of them followed vigorously. This phenomenon i s termed, by Jaynes, 'latent imprinting'; i t r e f e r s to the e f f e c t s of neonate experience that do not manifest themselves u n t i l l a t e r . In the case of the control groups (who were i n i t i a l l y exposed on days 12 or 13) the incidence of those reaching the c r i t e r i o n was zero. Although Jaynes c a l l s attention to the f a c t that behaviour i n the imprinting s i t u a t i o n includes f a r more than just following, he uses only t h i s aspect of i t i n setting up h i s c r i t e r i o n of imprinting. This i s reasonable, from one viewpoint, since t h i s aspect lends i t s e l f more e a s i l y to measurement than do the other types of behaviour observed. Since, however, the c r i t e r i o n i s l i m i t e d i n t h i s fashion, the term "latent imprinting" has meaning with reference only to the 71 following-behaviour, and i t cannot be decided whether the i n i t i a l exposure affected any of the other aspects of behaviour which might well warrant i n c l u s i o n i n the same category as the following-reaction. More of t h i s l a t e r , when the observations made during imprinting sessions have been presented. With reference to those birds that d i d follow as neonates, i t was the younger ones (at i n i t i a l exposure) which "forgot" ( i . e . , did not follow) on the second exposure, 10 days l a t e r . In f a c t , more than h a l f the birds i n i t i a l l y exposed before 12 hours of age "forgot" on the subsequent exposure, whereas none of the birds, i n i t i a l l y 2k hours or older when exposed, forgot on the second occasion. Since the i n i t i a l l y younger birds showed a higher incidence of following at that time, t h i s might appear surprising, but when i t i s r e c a l l e d that these younger birds, despite t h e i r higher incidence, showed less strong reactions, i f and when they did follow, than the older ones, the f a c t that more of them subsequently "forgot" i s to be expected. In a t y p i c a l memory experiment, the retention score i s usually p o s i t i v e l y correlated with the degree of o r i g i n a l learning, other things being equal (see Osgood, I960, page 556). Jaynes points out that these r e s u l t s indicate that there may be two c r i t i c a l periods, one i n which incidence w i l l be highest, the other i n which the e f f e c t s of the imprinting w i l l be maximal, (as seen when the birds are observed again 72 l a t e r i n l i f e ) . This i n t e r p r e t a t i o n enables the apparently divergent r e s u l t s of Fabricius (195D and of Ramsay and Hess ( 1 9 0 ) to be. reconciled. Fabricius obtained similar r e s u l t s as Jaynes f o r incidence, while Ramsay and Hess obtained a curve similar to that of Jaynes f o r retention. Not only i s there no contradiction, but also there i s both independent confirmation f o r Jaynes 1s r e s u l t s , and considerable support f o r h i s i n t e r p r e t a t i o n . The c r i t i c a l period, Jaynes comments, may depend upon not only the species and the imprinting procedures adopted, but also upon the way i n which the animals are incubated and reared, the nature of the stimulus, the duration of the imprinting session, and so f o r t h . Thus any given set of r e s u l t s must be interpreted r e l a t i v e to the p a r t i c u l a r group of animals, and to the conditions and procedures of the i n v e s t i g a -t i o n . Negative evidence f o r Hess's hypothesis (e.g., 1959)> that the end of the c r i t i c a l period i s determined by the appearance of f l i g h t reactions incompatible with following, i s provided by Jaynes. He states that some of h i s chickens f l e d on the t h i r d day, but were nevertheless imprinted, while others, who did NOT f l e e , were s t i l l not imprinted. Also, those (control) chickens, i n i t i a l l y exposed on the 12th or the 13th day, r a r e l y showed fear but neither d i d they follow. Thus, the determination of what i s involved i n the c r i t i c a l period i s by no means simple. Hess ( 1 9 5 9 ) found that chickens 1 locomotor a b i l i t y increased s t e a d i l y from hatching to about 1 6 hours thereafter; i t then l e v e l l e d o f f . The curve f o r the incidence of fear behaviour s t a r t s at about 1 0 hours and r i s e s to i t s maximum at 3 0 hours aft e r the chick hatches. By p l o t t i n g these two curves together, one find s that an area between the two curves i s arrived at which corresponds f a i r l y c l o s e l y to the area contained beneath the curve f o r the incidence of imprinting at successive ages of i n i t i a l exposure. The actual curve f o r imprinting incidence i s s l i g h t l y more narrow than that obtained by p l o t t i n g these other two together—Hess suggests that t h i s might be due to the r e l a t i v e u n s u i t a b i l i t y of the models used i n obtaining i t . These curves cannot be said to support the hypothesis i n question since they are but a more exact presentation of the data which gave r i s e to the hypothesis. I t i s true that the correspondence between these curves implies, at l e a s t , that the suggested r e l a t i o n between locomotor a b i l i t y , development of fear behaviour, and the c r i t i c a l period might well be v e r i d i c a l ; the negative evidence reported by Jaynes ( 1 9 5 7 ) , however, as well as that of Weidmann ( 1 9 5 6 ) , and of James ( 1 9 5 9 , I 9 6 0 ) , must also f i n d explanation, and i t i s d i f f i c u l t to see how t h i s can happen within the framework of Hess's explanation. 7k Jaynes ( 1 9 5 8 , a) provides further evidence that im-printing does not d i f f e r from learning. He found that increased practice, with maturation controlled, leads to the following r e s u l t s : 1 . The incidence of animals reaching the c r i t e r i o n i s higher during the l a s t f i v e minutes of a long exposure than i t i s during the same period of a short one. 2. In these periods, strength of following increases i n the long-exposure groups. 3. Tested at t h i r t y and seventy days of age, the animals which i n i t i a l l y had the longer exposures show.stronger following than the others. k. Longer i n i t i a l exposures lead to fewer fear responses on these subsequent t e s t s . 5 . Warm-up eff e c t s are observed when imprinted birds are tested af t e r an i n t e r v a l , and 6. Sex-difference i s not a s i g n i f i c a n t factor. These differences (except the l a s t ) were s t a t i s t i c a l l y s i g n i f i c a n t . Jaynes notes that chickens under barnyard conditions do not show, at these older ages, such attachment to the o r i g i n a l imprinting object ( i n th i s case, the parent). He suggests older chicks look more l i k e the parent, and " f i l i a l following becomes submerged i n general gregarious grouping" (p. 236). While v i s u a l distinctiveness may be relevant, i t should be noted that the experimental chicks did not see the green cube i n the 7 5 i n t e r v a l , whereas barnyard birds remain with the parent c o n t i n u a l l y — t h u s habituation may well account f o r the poor f i l i a l attachment of the barnyard animals, rather than lack of v i s u a l d i s t i n c t i v e n e s s . In h i s second 1 9 5 8 study, Jaynes found that, when a second target object replaces the f i r s t one, a decrement i n following occurs—except on the f i r s t day, when following scores to the f i r s t object are s t i l l low. This r e s u l t i s comparable to an e a r l i e r one (Jaynes, 1 9 5 6 ) . The magnitude of the decrement varies between i n d i v i d u a l s , but remains approximately stable f o r each i n d i v i d u a l over a period of four d a y s — i t i s NOT r e l a t e d to the strength of following the more f a m i l i a r object. The r e l a t i v e amount of generalization, based on group scores, s i m i l a r l y remains stable, between the second and fourth days (the animals being tested once per day). With regard to discrimination between the f a m i l i a r object and a l e s s f a m i l i a r one, on the f i f t h day, the s i g n i f i c a n t finding was not simply that discrimination occurs, but that i t emerges as the b i r d remains i n the runway, with both objects moving i n the same fashion. At f i r s t the animal may respond to both the f a m i l i a r and the "new" object, but a f t e r about t h i r t y minutes, i t i s responding to the f a m i l i a r one almost exclusively. This discrimination occurred more ra p i d l y with the birds which showed l e s s generalization during the e a r l i e r part of the experiment ( i . e . , during the f i r s t four days of t e s t i n g ) . The work of Moltz and Rosenblum ( 1 9 5 8 ) w i l l be referred to i n Chapter IV, i n connection with Moltz !s theory on imprinting. 7 6 James ( 1 9 5 7 , I960) found that chicks would approach a stationary object placed near a f l i c k e r i n g l i g h t at one end of a runway. When the chicks, at seven days of age, and with practice at the above behaviour on f i v e successive days, f i r s t saw the object move, they followed i t , much as chicks follow moving objects i n the usual imprinting s i t u a t i o n . An important point was that the normal c r i t i c a l period f o r chicks (roughly up to two days) was thereby extended. James was able to show, further, that the behaviour i n t h i s f l i c k e r - i m p r i n t i n g s i t u a t i o n varied i n strength as a function of age (at i n i t i a l exposure) and of rate of f l i c k e r . A high f l i c k e r rate was more e f f e c t i v e than a low one, and chicks who were 2h hours old at the time of the i n i t i a l exposure performed more strongly than 7-day-old chicks. I t i s suggested i n the e a r l i e r paper that f l i c k e r and movement, due to the c h a r a c t e r i s t i c s of the chicken's eye (see also Moltz, i 9 6 0 ) , are perceived i n e s s e n t i a l l y the same fashion, i n which case the f l i c k e r - i m p r i n t i n g s i t u a t i o n would be hardly d i f f e r e n t from the t y p i c a l imprinting one. I f t h i s i s so, then James's r e s u l t s indicate that overt following, or the expenditure of e f f o r t (Hess, 1 9 5 6 / 5 7 ) i s not e s s e n t i a l f o r imprinting to be e f f e c t i v e . A similar negative conclusion follows from the r e s u l t s obtained by Moltz, Rosenblum and Stettner (unpublished, c i t e d by Moltz, i 9 6 0 ) . These inv e s t i g a -tors kept Peking ducks i n an apparatus designed to r e s t r i c t t h e i r movement, but allowing a clear view of the moving target-object. After three, 25-minute exposures i n t h i s apparatus 7 7 (one per day), the ducks were subsequently released and "responded i n a manner indistinguishable from control Ss that had been a c t i v e l y pursuing the object for an i d e n t i c a l period of time." I t would be in t e r e s t i n g to set up an apparatus whose walls could be made to move around, while the target-object remained s t i l l . The young birds could either be confined a short distance from the target-object, and then released, or they could be allowed to move f r e e l y from the s t a r t . Would they move to the target-object or to the moving walls? I f they moved to ce r t a i n target-objects, but not to others, the most e f f e c t i v e objects could be established, at l e a s t , and t h i s might provide further evidence with regard to the hypothesis that energy-expenditure i s both necessary f o r following and p o s i t i v e l y correlated with the effectiveness of imprinting. Hinde (196l) points out that: Under natural conditions, the behaviour patterns operating between parent and o f f -spring are complex and diverse, and there are innumerable opportunities f o r associative con-di t i o n i n g to the mother during following, brooding, feeding, etc. As a r e s u l t of these a personal knowledge of the parent Is b u i l t up i n which the e l i c i t i n g s t i m u l i f o r the various discrete responses are united. In contrast with t h i s , he notes that: In c a p t i v i t y , the various juvenile r e -sponses may be attached to diverse objects, so that conditioning to a parent-companion does not occur. This suggests that the 'parent-companion 1 i s merely a consequence of the mother's presenting s t i m u l i f o r the 78 various juvenile responses, and not of any-inherent mechanism i n the young. In connection with the properties of objects to which the behaviour of young animals i n c a p t i v i t y w i l l be directed, Hinde ref e r s to Harlow's ( 1 9 5 9 ) finding that "conventional rewards are of l i t t l e importance." I t i s worthy of note, however, that c l o t h w i l l hold more heat than w i l l wire, and that a c l o t h model presents a more continuous, and therefore greater ( i n extensity) degree of warmth than does a wire model—assuming that the temperature ( i . e . , i n t e n s i t y ) of the two models i s the same. This might well be a factor i n the preference shown by Harlow's monkeys f o r the c l o t h models. The relevance of temperature changes to imprinting w i l l be discussed i n Chapter IV . It w i l l be clear from t h i s review of the l i t e r a t u r e that, while imprinting has been extensively investigated i n the l a s t decade, there are few examples of intensive analysis. As a r e s u l t of t h i s , not only has the phenomenon been made to include an extremely wide variety of forms of behaviour (e.g., Thorpe and Zangwill, 1 9 6 1 ) , and not only have at l e a s t three d i f f e r e n t theories been proposed to account f o r i t (Chapter IV), but also, and i n spite of both these s i t u a t i o n s , the nature of i t s underlying process or processes, and the i d e n t i t y of i t s components, have not been established with any great degree of assurance. Although i t i s not uncommon f o r the explanation of 79 a given form of behaviour to remain elusive, the description of i t s components i s usually beyond dispute. I t may happen that "motivated perception" leads to bias i n assigning relevance to behavioural components, while ignoring or discounting others, or, on the other hand, some components may be more obvious or more quantifiable than others. I t appears to the writer that the l a t t e r condition applies i n the case of imprinting. I t i s necessary, therefore, to e s t a b l i s h what e f f e c t an a r t i f i c i a l imprinting procedure has on the normal behaviour of the species. To do t h i s , the behaviour of animals i n the experimental s i t u a t i o n must be f u l l y described, as must that of animals i n a more natural setting. U n t i l the behaviour i n a r e l a t i v e l y free environment i s known, the e f f e c t of the experimental procedure on the animal cannot begin to be understood. The problem with which t h i s research w i l l be concerned, then, i s to describe the v a r i e t i e s of behaviour of newly-hatched chickens, under several d i f f e r e n t stimulus conditions outside the experimental s i t u a t i o n , to do the same f o r the behaviour of comparable chicks i n the imprinting s i t u a t i o n , to compare the behaviour observed i n the two si t u a t i o n s , and to consider the adequacy of the theories which have been proposed to account f o r imprinting, i n the l i g h t of these findings. 80 CHAPTER II METHODS AND PROCEDURES A. OUTSIDE THE IMPRINTING SITUATION (1) SUBJECTS AND THEIR INITIAL TREATMENT The subjects of t h i s observation were (a) 20 chicks of undetermined sex from the following species: New Hampshire, and White Leghorn, and (b) h broody hens, a cross between White Cornish and White Plymouth Rock, a d i f f e r e n t one f o r each of the respective groups. The broody hens were taken by hand from the i r outdoor houses, i n which there were laying/nesting boxes and several other hens (usually approximately s i x per house). Most of the other hens i n the house were not broody, and the hen used had been laying up to within about one week of i t s removal for use i n th i s study. None of the hens had ever hatched or reared a brood of chicks. They were approximately one year old, and were removed by an experienced poultry man. This minimized the disturbance to the hen, who, nevertheless, was c l e a r l y aroused to no mean extent by her removal. She was car r i e d indoors, to the room i n which the apparatus was set up, and placed i n the observation pen, with one or more chicks. The chicks were hatched i n a forced a i r incubator, the eggs being placed i n i n d i v i d u a l wire-mesh cages two days before they were due to hatch. The temperature i n the incubator was 9 2 to 9 ^ degrees Fahrenheit, and the humidity was between 82 81 and 8*+ per cent. There was a small glass panel i n the door of the incubator, which allowed some l i g h t to enter. The chicks were taken out of the incubator at, or soon a f t e r , hatching; the top of each wire cage was opened, and the s h e l l was removed; the chick was then car r i e d i n the wire cage to nearby scales, removed by hand from the cage, placed on the scales, and returned by hand to the cage. I t was ca r r i e d , i n the cage, about *f0 f e e t , and placed i n the observation pen, where i t was removed from the cage by hand and placed underneath the lamp. One chick, i n one of the groups, was indistinguishable from another i n the same group, so i t was marked with a piece of white tissue-paper, fastened to the middle of i t s back with adhesive tape. On i t s journey to the observation pen, the chick passed through a room i n which a large number of hens and some cockerels were i n d i v i d u a l l y caged, and who were continually engaged i n producing the vocalizations regrettably t y p i c a l of th e i r kind. I f the chick, or group of chicks, was to be observed i n the company of a broody hen, the hen was brought to the observation pen ten minutes a f t e r the a r r i v a l of the chi c k ( s ) . In the case of a group of chicks the cages were carr i e d one on top of another, with one chick inside each. The temperature i n the observation pen was 95 degrees Fahrenheit underneath the lamp (plus or minus two degrees), and about ten degrees below t h i s at the furthest point i n the pen from the lamp. Humidity was not measured, but i t was considerably 82 lower than i n the incubators. The bulb of t a 60-watt reading lamp was positioned about f i v e inches above the f l o o r of the pen and the shade was i n c l i n e d so that the l i g h t and heat from the lamp were r e f l e c t e d s l i g h t l y forwards ( i . e . , i n the d i r e c t i o n of the observer's usual position) as w e l l as downwards. The lamp remained on both by day and by night. The main l i g h t s i n the room were never switched on, but the i l l u m i n a t i o n varied with the time and type of day or night, as windows were found i n one wall of the room, near the observation pen. Food and water were always present i n the pen. (2) APPARATUS The f l o o r of the observation pen consisted of the top of a large wooden table, s i x feet by four feet i n area, and three feet above the f l o o r . Walls of chicken wire, supported by a wooden frame, were nai l e d to the sides of the table on a l l sides, and extended upwards f o r three f e e t . The roof was similar to the walls, and could be s l i d across the top of the wooden frames supporting the walls; i t was of the same area as the f l o o r of the pen. Along one end and one side of the pen, on the outside of the wire walls, black plywood sheets were nailed. The one at the end covered the entire width of the pen, and extended upwards, from the l e v e l of the f l o o r of the pen, fo r two and one-half f e e t . The plywood at the side joined t h i s end piece, and covered one w a l l , along the length of the pen, except f o r a space of eight inches; i t , too, had a height of 8 3 two and one-half feet above the pen f l o o r . The other side, the other end, and the roof of the pen, had no such plywood, just the chicken wire mentioned. These w i l l be termed "open". The open end of the pen faced the windows, standing s i x inches from them. The bottom of the windows was 2k inches above the l e v e l of the f l o o r of the pen. The open side of the pen faced a large piece of unused wooden equipment along i t s entire length; the equipment extended upwards fo r two and one-half feet above the f l o o r of the pen--above and beyond t h i s was one of the white walls of the room. The pen was s i x inches from th i s wooden equipment, which, l i k e the f l o o r of the pen, was dark brown i n colour. At one point above the closed side of the pen extended a s t i c k , on which was placed a silver-coloured microphone, with a black t r a i l i n g lead disappearing from the chickens 1 view downwards outside the black plywood on that side of the pen. A black e l e c t r i c cable, with a grey extension socket-box, lay on the roof, and a piece of brown f l e x ran.from t h i s across another part of the roof, and down, through one of the holes i n the chicken wire, to the lamp on the f l o o r of the pen. The lamp was of brown metal, with an adjustable arm, and a heavy base. The inside of i t s metal shade was silver-coloured, the outside being brown l i k e the r e s t of the lamp. The area on the f l o o r below and s l i g h t l y forward of the bulb, onto which the l i g h t and heat were focussed, was circumscribed by a continuous chalk mark which thus delineated a c i r c l e of six-inch radius, referred to as area one. Beyond t h i s c i r c l e , and concentric, with Oh i t , two further c i r c l e s were marked, three inches, and s i x inches outside the f i r s t — t h e s e are areas two and three respec-t i v e l y . The base of the lamp was i n part of area three, and the bulb was above area one, as mentioned e a r l i e r . Three inches to one side of the base of the lamp, also i n area three, was a small Petrie dish containing water ( t h i s i s c a l l e d "the small dish" i n the descriptions of behaviour), three inches to the opposite side of the lamp, again i n area three, was a larger glass dish, three inches high, also containing water (mainly f o r the hens, while the smaller one was provided f o r the use of the chicks). On the opposite side of area one, once more i n area three, were two further dishes, similar to the f i r s t two, containing food. Some grains of food were scattered a l l around the intervening (and other) areas, and whenever the water was changed ( n i g h t l y ) , some of i t was allowed to f a l l on the f l o o r near the two water dishes. As three large holes had been d r i l l e d at some e a r l i e r date, into the table, which constituted the f l o o r of the pen, three t h i n pieces of wood (approximately s i x by four by one-quarter inches) were nai l e d over them. These were well outside area three, and one of them (near the observer's usual position) w i l l be referred to i n the descriptions of behaviour, i n connec-t i o n with the r e l a t i v e ease with which the animals mounted i t . Outside the observation pen, on the closed side, was a smaller table, with a chair and a s t o o l on i t . These were used by the observer i n the course of h i s observation. The chair 85 was positioned i n such a way that the observer could speak into the microphone above the wall of the pen, without taking h i s eyes off the animals; the st o o l could be used to r e s t paper, etc. on -wrhile making written notes. As the f l o o r of the room was of concrete, the legs of t h i s smaller table were cushioned with several paper towels, to reduce the chance of them scraping along the f l o o r , thus making a sudden loud noise. The chair and stool-legs were s i m i l a r l y cushioned. To t h i s same end, the observer removed h i s shoes when i n the observation room, and the door into the room was always moved gently. The black plywood on two of the walls of the pen enabled the observer to move around the room without disturbing the chickens. The side table (with the chair etc. on i t ) was positioned three inches; from the observation pen, which allowed the observer to step onto i t without j a r r i n g the pen. The top of the observer's head appeared above the plywood when he watched the birds, or, occasionally at the side of the plywood running along the length of the pen (with the gap of eight inches). A tape recorder was placed on a t h i r d table, s i x feet from the observation pen, on the "closed" side. (3) PROCEDURE DURING OBSERVATION After the subjects had been placed i n the observation pen, as described above, (which required the observer to stand on the table outside the p e n — t h i s table to be c a l l e d the 86 observation t a b l e — w i t h both arms and one leg reaching into the pen), the observer stepped out of the pen, s l i d the roof over the top of the pen, climbed down and switched on the tape recorder. The roof made a f a i r l y loud noise when i t was moved, and the tape recorder gave a loud c l i c k as i t was switched o n — i t was almost s i l e n t while running. The observer then stepped back onto the observation table, keeping h i s head below the top of the plywood, and sat on the chair, or knelt or squatted on the table. He then slowly raised h i s head to a pos i t i o n i n which the subjects could be seen, and reported what he saw into the microphone, after f i r s t describing the group being observed and the age of i t s members. The behaviour was observed and recorded i n t h i s fashion i n periods of twenty-five minutes, with a five-minute break between each of these. Occasionally, the observer would move off the table and observe from a d i f f e r e n t point above, or to the side of the plywood. At such times, he would be standing on the f l o o r , and could just see over the top of the plywood. I f observing from the side, he allowed only the smallest possible amount of h i s person to protrude beyond the plywood, where the subjects might see i t , and, just as when observations were made from the usual position ( i . e . , on the observation table), the observer's head was moved as slowly as possible out beyond the plywood. The microphone could be moved from the s t i c k above one wall of the pen, without j a r r i n g the pen. In addition to the descriptions spoken into the microphone, the observer, from time to time, wrote comments (usually a 87 comparison with the behaviour of another group) on the behaviour observed. The food i n the pen was changed only when no chickens were p r e s e n t — i n other words, between groups. The pen was l i k e -wise cleaned between groups. The water was changed l a s t thing at night, i n the following fashion: a hose was pushed through the chicken-wire roof to each water dish i n turn; the water was allowed to run for about one minute, which ensured that a l l the old water was forced out, and that new water took i t s place. The water which overflowed from the dishes ran to the near end of the pen, and f e l l down to the f l o o r , flowing to a nearby drain. After t h i s , the water was turned o f f , and the hose removed. The water dishes were thoroughly cleaned between groups. O f ) GROUPS OBSERVED Table 1. L i s t of groups observed outside the Imprinting s i t u a -t i o n . The groups were observed i n the order shown. GROUP NO. NUMBER AND TYPE OF MEMBERS 1/0 One chick with no broody hen. One chick with one broody hen. 2/6 Two chicks with no broody hen. 2/1 Two chicks with one broody hen. 3/0 Three chicks with no broody hen. 3/1 Three chicks with one broody hen. h/0 Four chicks with no broody hen. h/1 Four chicks with one broody hen. 88 (5) OTHER RELEVANT FACTORS a. Noise During the entire course of the observations almost continuous noise was made by the many chickens including some cockerels housed i n adjacent rooms. With the door closed, t h i s was much reduced within the observation room, but when the door was opened i t became momentarily much louder, u n t i l the door was closed again. .'Oftena soft hum, from e l e c t r i c a l machinery operated at the f a r end of the building, could be heard. For much of the day, a radio played i n another part of the b u i l d i n g — t h i s could only be heard when the door was open, and then but f a i n t l y . When equipment was moved (usually by being r o l l e d ) from one part of the building to another, t h i s could be h e a r d — e s p e c i a l l y when i t came close to the observation room. There was a telephone i n an adjacent room, which sometimes rang, and, on occasion, one person might c a l l to another i n some part of the building. Several times a week, groups of school c h i l d r e n would v i s i t the poultry farm—these, too, tended to cause an increase i n the noise l e v e l f o r a while. Sometimes someone, or something, would knock against a wall i n an adjacent room. On three or four occasions, the door to the observation room was opened by someone other than the observer, and the other person spoke to the observer, from the doorway. Twice someone entered to f e t ch something from a cupboard. 8 9 The continuous noise of the nearby fowl constituted by f a r the most common source of noise. I t was by no means loud,—when the hearer was i n the observation room with the door closed, at l e a s t — b u t i t served to mask most of the other, occasional, noises. The f a c t that the observer almost immediately habituated to i t upon entering the room serves as a rough i n d i c a t i o n of i t s strength, or of i t s nuisance-vialue. This noise was much reduced at night. When the observer used the microphone, h i s voice.was heard, of course, by the subjects. b. V i s u a l Disturbances Neither the chicks nor the hens could see out of the windows at t h e i r own l e v e l — t h e y could see the sky, and probably the roof of an adjacent building as they looked upwards through the windows. Their v i s i o n was not disturbed i n any other way except by the hose, when the water was replenished n i g h t l y , and by the slow movements of the observer's head as i t moved out from behind the plywood at the walls of the pen. To the observer's knowledge, nobody came close enough to the windows to be seen by the chickens i n the pen, nor did anyone, other than the observer, look over the plywood into the pen, except when one of the s t a f f of the poultry farm brought i n the broody hens. There was scarcely any a c t i v i t y i n the area outside the windows. c. Smell The usual sort of smell associated with a poultry farm pervaded the observation room at a l l times. I t i s thought not 90 to be important to any great degree. d. Handling The subjects were not handled except at the beginning and end of the period i n which they were i n the observation pen. Their i n i t i a l handling was discussed e a r l i e r . e. Length of Observations Each group was observed i n t e n s i v e l y f o r at l e a s t two days. I f the next group was not ready by then ( i . e . , when the eggs did not hatch quite on time), observations were continued. Since the observer frequently found that, i f he attempted to watch i n d e t a i l the behaviour of the chickens f o r a continuous period of more than about two to three hours, he began to miss possibly s i g n i f i c a n t d e t a i l s , the observations were postponed aft e r t h i s length of time, and were resumed t h i r t y to si x t y minutes l a t e r . Likewise, observations were necessarily discontinued when the observer went home f o r the night. B. IN THE IMPRINTING SITUATION ( 1 ) SUBJECTS AND THEIR INITIAL TREATMENT . Twenty-six newly-hatched New Hampshire chickens, of undetermined sex, were the subjects i n the imprinting part of t h i s study. They were hatched i n the same way as the previous 9 1 chickens, being taken from the incubator at between f i f t e e n minutes and two hours a f t e r hatching. They were placed i n separate covered cardboard boxes, or i n separate compartments of a large covered cardboard box, which had holes i n the roof f o r v e n t i l a t i o n , and transported i n the back of a car f o r about one mile to the imprinting room. They remained i n these boxes, or compartments, which were numbered, throughout the whole of t h i s part of the study, except when taken to the imprinting runway. In these boxes, the chicks could hear, but could not see each other. The temperature i n their immediate v i c i n i t y was around 9 6 degrees Fahrenheit, and the humidity i n the room was low. Food and water were always present i n each bird's compartment or box, these were replenished at the end of each day. The room was generally quiet, with the occasional noise of people passing along the corridor which ran around three sides of the room (the floors were wooden) and of t h e i r speech at such times. The experimenter removed h i s shoes whenever he entered the room. (2) APPARATUS A wooden, black-walled, runway, eight and one-half f e e t long and two feet wide, with twenty-two inch high walls, was used. I t was s t r a i g h t , and i t s f l o o r was covered with wood shavings to an average depth of about one-quarter inch, although these tended to c l u s t e r , and so b u i l d up to almost an inch i n depth. Two pulley wheels were situated, one at each end of the runway, at the top of the apparatus, being supported by black wooden 92 cross-members. A black pulley b e l t ran around and between the wheels, and the drive came from a variable-speed e l e c t r i c motor, just outside one end of the runway, being relayed by a black drive b e l t onto one of the pulley shafts. The motor made a s l i g h t hum when i n operation. Suspended by a light-coloured thread from the pulley belt, was a yellow p l a s t i c i m i t a t i o n golf b a l l (for the f i r s t group), or a v e r t i c a l l i n e of such b a l l s (for the second group). In the l a t t e r case, a white b a l l was at the top, with a yellow b a l l beneath i t , a second yellow b a l l beneath that, and a red, white, and blue banded rubber b a l l , of the same size as, but heavier than the others at the bottom of the l i n e . These target-objects cleared the f l o o r by l e s s than one inch i n the middle of the runway, and by about two inches under each pulley wheel. The runway had no sp e c i a l l i g h t i n g as i t was situated d i r e c t l y beneath two flourescent tubes i n the (high) c e i l i n g of the room. These ran across the runway, and, as both these and several other nearby flourescent l i g h t s were on during the day, the runway was well and evenly l i t . A continuous tape, with a human re n d i t i o n of "Gock, gock, gock" was played on a tape recorder, at the times shown below. The tape recorder was placed i n such a way that the sound was maximal i n the centre of, and below, the runway. The volume was reasonably high. In the runway the temperature was approximately 10 degrees below that i n the chicks' l i v i n g quarters, which were near a radiator. 93 (3) IMPRINTING PROCEDURE The chicks hatched i n two groups, three days apart. Thirteen chicks hatched and were used on the f i r s t day, the other t h i r t e e n on the subsequent day. The only difference i n the conditions lay i n the target-object, mentioned above. The second group of chicks had a mean age one hour greater (four hours) than the f i r s t group (three hours). Each chick was taken by hand from i t s box, c a r r i e d to the runway, and placed i n the centre thereof. The target-object was motionless at one end of the runway, and no sound was coming from the,tape recorder. After f i v e minutes the recording of "gock" was switched on, and aft e r two more minutes, the pulley was set i n motion, with the "gock" s t i l l playing. This lasted for ten minutes, when the sound was switched o f f ; then, a f t e r a further two minutes, the pulley was stopped near one end of the runway. The chicken remained i n the runway f o r one f i n a l minute, when i t was removed by hand, and returned to i t s box. The pulley moved at a speed of approximately sixteen feet per minute, completing one c i r c u i t i n a f r a c t i o n l e s s than a minute. Thus, when the chick was i n the centre of the apparatus, the target-object passed him twice each minute, at 30-second i n t e r -v a l s ; when the animal was at one end of the runway, i t passed him once per minute; between these two extremes the object passed him twice per minute, each pair of passes being closer together, and separated by a longer i n t e r v a l , the nearer the b i r d 9h was to the end of the runway. The target-object swayed from side to side as i t moved along the runway. The age at which an individual chick was exposed to the moving object varied from one and a half to six hours after hatching. The experimenter observed the chick's behaviour by moving the top of his head and eyes above the top of the walls of the runway (which rested on a table), and at a distance of from two to four feet from them. He recorded the behaviour by means of symbols, and then wrote a f u l l report immediately after the particular chick was returned to its box. Gn the day following this i n i t i a l exposure, the chicks were again placed individually in the runway for a period of ten minutes. Wo sound was used; the target-object was the same as on the f i r s t day, and was in the process of moving around a pulley wheel at one end of the runway as the chick was placed in the centre, facing that pulley wheel. The target-object did not stop moving during the entire period in which the chick was in the runway. 95 CHAPTER III RECORD OP OBSERVATIONS A. Outside the Imprinting Situation The behaviour of the subjects was described as i t occurred. The observer spoke into a microphone, and the observations were recorded on tape. Subsequently, these re-cordings were transcribed onto paper. Each thirty minutes of observation required approximately five pages when transcribed, and each of the eight groups was observed for about fourteen hours in a l l . Thus, to present the complete verbatim descrip-tions, over one thousand pages would be needed. Because of this, the behaviour of each group is summarized. ( 1 ) Observations of the behaviour of a chick s t i l l  inside the (chipped) shell. The following written notes were made: There is a small hole in the shell; the beak is protruding slightly through this hole, with the side of the beak pressed against the edge of the shell. Only part of the head and upper body can be seen—there are rhythmic breathing movements involving the whole of this vis-ible area. The beak opens and closes fairly frequently—usually a series of 5-6 such movements is observed, lasting about 3 seconds, and followed by a pause, in which the beak is closed, of about 1 2 seconds' duration. The head moves slowly and irregularly, to both sides, up and down, forwards and backwards. The beak sometimes goes back into the shell as the head moves. The visible area of the chick often jerks two or three times. This continues at irregular intervals (approximately between 5 and 1 0 seconds), for most of the time. On many occasions a single soft chirp is heard, or a short series of such chirps. This sound is the same as the soft chirps of newly-hatched chicks. There is usually a long interval between such chirps, or between the series of chirps. 9 6 The egg was moved forwards, by hand, and loud chirping was heard—6 chirps, louder and longer than the ones mentioned above. Approximately 2 0 seconds later, when the egg was s t i l l , there was another such series of loud chirps. Thereafter, the chirping was quieter, and the same as the earlier chirping. The mouth continued to open and close more frequently at later periods; these movements were slower than similar ones of a newly-hatched chick. ( 2 ) Behaviour between0 incubator and observation pen  (all groups). When the door of the incubator was opened, the chick would usually be lying in one corner of its wire cage. Its head was almost always turned towards the now-open side of the incubator; its eyes were open; and i t was quiet. Sometimes i t would be standing in the cage when E f i r s t saw i t , or i t would stand up (or at least push up on its legs) soon afterwards. As E put his hand into the incubator to l i f t out the wire cage, S would look upwards towards the approaching hand. The cage usually scraped slightly along the wire floor of the incubator as i t was lifted forward—as i t was brought forward, S would sway and/or shift its feet, probably to keep balance. The chick would watch E's hand as he opened the top of the wire cage,.and reached inside to remove the halves of the shell. If the shell brushed against the chick, i t would flutter to one side, and give a single moderately loud ca l l , or a few such calls. As the chick was being carried to the scales, i t usually lay down, with body flat, but head up, looking around. It might, however, stand, with head moving about. In both cases, the chick would remain quiet at this time. As E reached in to pick up the chick for weighing, i t watched E's hand. It did not move from whatever position i t was in, but as E took i t in his hand, i t would shuffle about, pushing itself backwards across E's hand, and giving several loud calls. If E did not get i t success-fully on this f i r s t attempt, i t would run around the small cage as E reached towards i t again. It was not uncommon for the chick to peck lightly at E's hand at such times. As soon as i t was placed on the scales, i t settled down, body flat, head at medium height (beak horizontal). As E lifted i t off the scales and re-turned i t to its cage, i t would struggle in his hand; i t usually made no sound at this time. Back in its cage, i t would settle down immediately, body flat, head at medium height, looking a l l about, and i t remained like this while being carried to the obser-vation pen. One or two chicks would stand instead of lying in the cage, and, occasionally, one or more soft chirps would be heard. It did not show any particular response as i t was being carried through the room in which the many older noisy chickens were in-dividually housed. When E reached into the cage to l i f t the chick into the observation pen, i t would usually struggle in E's hand, 97 and might call moderately loudly once or twice. It would l i e down immediately, in most cases, or would stand where i t had been placed—in either instance, its head would be held at medium height, and i t would look around in several directions. At this time i t made no sound. As E climbed out of the pen, the chick would, normally, turn and look in his direction. As the roof was slid over the walls, a noisy operation, the chick would stand up and move quickly forward, or around, a few paces, fluttering i ts wings, and calling loudly. This calling continued as E climbed down, switched on the tape recorder, and took up his position—by this time, or soon afterwards, the chick usually was quiet and lying down, with head up and eyes open, near the lamp. (3) Group I/O; one chick, with no broody hen. Until about 3 hours old, S spent most of its time lying flat on the ground underneath the lamp. Its beak and head were stretched along the ground in front of its body, and its eyes were closed. Its back was towards the lamp. It would raise its head and open its eyes for a few seconds—infrequently—and would shift position slightly, from time to time, without standing. At these times a few soft chirps might be heard, while, for the rest of the time, the chick would make no sound. As i t grew older, the length of time i t spent lying on the ground decreased. After such a period i t would stand, stretch its whole body, flutter its wings, gape a few times, and move jerkily forward a short distance. Its legs, for the f i r s t few hours, were not straight underneath i t , but were slightly bent. This meant that the bottom of its body was slightly lower than the top of its legs. Its head would be held mostly at medium height (i.e., beak horizontal), and would jerk slightly in several directions. If i t stood s t i l l , its body would sway forwards and backwards, and to each side—on occasion, i t would almost lose balance, but would quickly regain i t , using its feet and wings in particular. Often its head would be held just above the ground, moving to the right and left as i t stood or walked forward. At f i r s t , i t rarely pecked at the ground, but within a few hours, this was done almost the whole time as i t stood or walked forwards, or as its body lay on the ground, with head up. When i t walked, the leading foot would not fully advance to the front of the trailing one, so that i t often lost balance, walked jerkily, and had slight difficulty in retrieving the foot that was partly pinned down by the other one. By about the age of Ik- hours, i t no longer did this. Most of its pecking occurred in fairly long bursts, a l -though shorter bursts, or single pecks, were observed during most of the time between its 'rest' periods. After each peck, or after 9 8 two or three peeks, its throat would move rhythmically for a few seconds, with its mouth remaining closed—this is referred to as "chobbling". After most pecks i t would give a single soft chirp. A typical sequence was peck-chirp-chobble, repeated many times. Between a burst of pecking i t would raise its head (beak above horizontal) and look around in several directions, and might walk forwards, or around, before resuming pecking, although i t moved a l i t t l e almost continually as i t pecked. As i t raised its leg to step onto the Petrie dish con-taining most of the food (a lot was also scattered on the ground),or to step onto one of the raised pieces of wood in the pen (see the description of apparatus), i t would often lose balance, and, on these occasions might actually f a l l onto the ground, although i t immediately regained balance, by using its legs and wings in parti-cular. During these f i r s t few hours, i f . i t was resting, the crowing of a cockerel in the next room, and the ringing of a telephone in another adjacent room did not disturb it—even though both these sounds were intense and sudden enough to startle the observer. If these occurred during one of its active periods, however, a startle response would be seen. This, consisted of the following pattern: the chick would stop whatever i t was doing at the time; its head would jerk up, and would be held, cocked slightly to one side, with eyes fully open, and mouth closed, and with beak well above horizontal. Its head would usually remain s t i l l in this position, or would, less commonly, jerk slightly to a different position, to the right or left.. The chick would remain quiet and s t i l l . This response would last for no more than five seconds, unless the noise persisted in short bursts (e.g., the continued crowing of a cockerel). The chick would then continue with its previous behaviour, or would walk forwards a few paces, head at medium height, and looking around or towards the ground, before resuming its previous activity. This startle response was shown throughout the whole period, in which the chick was observed; i t was also.common to a l l the chicks,, and a similar pattern was Shown by the broody hens in like circumstances. If the chick's body happened to be on the ground, i t would f i r s t move its head, as described, and would often stand up as well. Loud calling was seldom heard, after the chick was once placed in the pen. If the chick had moved well away from the lamp (this did not occur for some hours), and had remained there for several minutes, a few loud calls might be heard. At the same time, the chick would raise its head high into the air, look a l l around for some seconds, turning its body as i t did so, and then run, with wings extended slightly and fluttering, back towards the lamp. It would then move slowly around beneath the lamp, for a few seconds, with head mostly near the ground, and then l i e down under the lamp. A few soft chirps might be heard as i t moved around 99 beneath the lamp. Such sudden runs were rare, and sometimes occurred in the opposite direction (i.e., away from the lamp, or at least, across the pen around area three)i The Chick was seen to peck at the grains of food, at foreign particles on the ground, at the black plywood walls, at the head of the nails in the raised pieces of wood, at the side of the glass water dishes (apparently at the bubbles in the water), at the thermometer, at the base of the lamp, at the inside of the shade on the lamp, at the water in both the large and small dishes (never at the drops of water on the ground), and at its faeces. When i t peeked at the water for the f i r s t time (several hours after being placed in the pen), i t had been pecking at the side of the water dish a moment e a r l i e r — i t appeared as though the chick was pecking at the bubbles in the water, rather than at the water itself, for, as soon as i t had pecked into the water, i t raised its head, and maintained the startle pattern for a few seconds, before chobbling, looking down towards the water again, and pecking into i t several times more. When i t pecked at its faeces, i t would raise its head quickly, making a peculiar kind of soft squawk, open and close its mouth several times, shake its head vigourously, and flutter its wings, bringing them forwards, its head moving underneath one of them. This f i r s t happened when the chick was about k 1/2 hours o l d — i t occurred again twice on the f i r s t day, several hours later, and once on the second day of observation. The chick defecated very infrequently on the f i r s t day, somewhat more often on the second. When the observer replenished the water in the two dishes, at the end of the f i r s t day's observation, the chick squawked and called loudly as the hose banged the wire of the roof. As the hose came down towards the water dishes, these loud calls continued, and the chick ran, from beneath the lamp, across to the far side of the pen, about 4- feet away from* the water dishes. There i t stood, watching the operation quietly. As the hose was pulled back up towards the roof, the loud calling began again, and the chick ran to the side of the pen. Within 2 or 3 seconds of the hose's disappearance, the loud calling ceased,, and the chick moved slowly back to area one. As the chick grew older, not only did i t spend less time lying on the ground beneath the lamp, but also its movements (es-pecially Its standing, walking, preening and running) became better controlled, and less likely td lead to loss of balance. When i t did lose its balance, this was regained before the chick's body actually hit the floor. Its walking became slower, and larger strides were used, with each foot remaining in the air for a longer period than at an earlier age. Its running was faster, 100 and more frequent. When i t stood, i t swayed less, its legs were straighter underneath i t (hence its body was higher), and i t re-mained standing for longer periods. When i t preened in the standing position, i t maintained much better balance. During the f i r s t two hours, the chick shivered, and pulled its wings close into i t s body, almost continuously. This occurred less with increasing age, and was not observed after about five hours. The chick's breathing movements seemed to involve, or to affect, almost the whole of its body, when i t was very young— later, their effect was not so apparent, although the movements were s t i l l quite obvious. As the chick grew older, the soft chirps became both easier to hear, and more common, especially as i t moved about and pecked. The distance covered, and the distance to which the chick would move away from the lamp, increased with age. As the observer began speaking into the microphone at the start of each twenty-five-minute period, the chick would show the startle pattern, then look in his direction. Within about five seconds, i t would cease to orient its behaviour towards the observer, and appeared to pay no further attention to his voice—unless i t had been lying down for several minutes, with the observer quiet, and then the observer had spoken again (e.g., to confirm that the chick was s t i l l lying down, or to record the fact that i t had shifted position slightly)—on such occasions, the chick would show the beginnings of the startle response pattern, but would quickly cease to do so. If the chick had been lying down under the lamp from the end of one such observation period to the start of the next (i.e., a period of between 5 and 10 minutes) i t would often stand up and begin to move around almost as soon as the observer began speaking again, settling once more within 1 to 2 minutes. It seldom appeared to hear the ob-server as he climbed onto the observation table, or to see his head as he moved i t upwards above the walls of the pen. Quite frequently, at a l l ages, the chick would preen, or peck at, various parts of its body, and scrape the side of its beak along the ground (this last item was not observed until the second day). Most commonly, the chick would preen behind one or other of its wings; almost as frequently, i t would preen its breast; somewhat less often, i t would preen its stomach between its legs, or at the inside of one leg. As i t preened behind a wing, this wing would be pulled forwards, and the opposite wing would move outwards from the chick's body—its legs would be spread slightly further apart. After preening, i t would usually shake its head once or twice, and open its mouth (gape) a few times. 1 0 1 Quite often, the chick would raise one foot towards its beak, and peck at any dirt etc. on the foot—on these occasions i t frequently lost balance momentarily, and replaced its foot onto the floor as in regaining i t . At a l l ages, the chick occasion-ally stretched one or other of its legs straight back behind i t , clear of the ground, with foot spread out, swaying slightly forwards on the other foot as i t did so, and stretching its head forward, mouth often opening. The foot would be held in this position for up to about five seconds. (k) Group 1 / 1 : one chick with one broody hen. The behaviour of the chick was comparable to that of the one in group 1 / 0 , with the following added features: When the hen was placed in the pen, some ten minutes . after the chick had been put in i t , she clucked and squawked very loudly, flapped her wings, ruffled her featheis, jerked her head around sharply, looked up towards the top of the pen (as the roof was being closed), and walked over to the far end of the pen, away from the lamp, chick food, etc. She stood there, looking out of the wire netting, squawking and clucking inter-mittently, scratching her feet on the ground, feathers slightly ruffled and t a i l up. She continued in this fashion for several minutes, strutting along the wire, and occasionally placing one foot on the wire and hopping up onto and against i t . The chick showed a marked and prolonged, startle response as the hen arrived (the hen made such a noise that any calls that the chick made were obscured). It had been lying under the lamp, with head up, and now stood up, watching the activity of the hen closely. It moved around on the same spot, as the.hen walked to the far end of the pen, and, at this stage at least, gave no calls. As the hen moved around, i t walked towards her,, as far as area three, then stood looking in her direction for several minutes, occasionally looking in several other directions as well, and down towards the ground. It then turned and moved towards the lamp (approximately 5 minutes after the hen's arrival), pecking at the ground as i t did so. In area one, i t stood looking towards the hen for about 1 5 seconds (the hen was standing s t i l l and quiet, looking out of the wire, away from the chick), and then turned from the. hen and lay down, with head up. It looked a l l around, then down at the ground in front of i t pecked and chobbled three times, and then its head slowly sank towards the ground, with its eyes partly closed. As the hen moved and clucked again, several seconds later, the chick's head jerked up, its eyes opened fully, and its head turned towards the hen. It watched her for a few seconds, 1 0 2 then looked towards the ground, pecked and chobbled once, then closed its eyes, with its head s t i l l up in the air and pulled back into its body. Similar behaviour was observed on the next few occasions when the hen squawked and/or moved around. The chick once stood up, turned further from the hen's direction, and lay down again, with head on the ground. About fifteen minutes after the hen's arrival, she lay down at the far end of the pen, head high in the air, looking out of the wire. Thereafter she remained like this for almost the entire day. Occasionally she would give a few soft clucks, and would jerk her head around a l i t t l e , especially i f there was a sudden noise. Both the hen and the chick jerked their heads up at a noise, instantaneously, and in an almost identical manner. The hen, however, remained with head up for far longer than the chick. Once or twice during the remainder of the day the hen stood up, stretched, squawked and clucked, walked forwards and settled down again. She also preened herself upon occasion. Just over one hour after the hen's arrival, the chick who had wandered into area three, away from the lamp, and in the hen's direction, pecking at the ground once dr twice, stood at the outer edge of this area, and looked towards the hen, some three feet away. The hen had been watching the movements of the chick during this time, with neither of them vocalizing. As the chick slowly moved two or three paces farther towards the hen, she stood up, clucking, and looking towards the chick. She walked about five paces across the cage, obliquely to the chick, s t i l l clucking and watching the chick, with her t a i l ruffled and spread out behind her. The chick stood swaying as the hen stood up, watched her as she began to move, lost balance, quickly regained i t , called loudly twice, and looked towards the hen, who by now was s t i l l . The chick slowly and irregularly walked towards the hen, sometimes looking towards the ground, and sometimes standing s t i l l . When about 1 8 inches from the hen, the chick stood looking towards her for a few seconds, then darted forwards to the side of the hen, near the front of its body. The hen, who had watched, the!,:chick the whole time, pecked at i t once, then peeked again and lifted the chick in her beak, and tossed i t away from her, some six inches. The chick gave a long loud call as the hen pecked the f i r s t time, shaking its head (the hen had pecked at the top of its beak, near one eye), and ran in towards the hen's legs. As the hen threw i t forwards, the chick gave several more long loud calls, kicked its legs and fluttered its wings, as i t struggled to stand upright. It stood, calling loudly, shaking its head,and preening its breast, for about 3 0 seconds, then stood quietly looking towards the hen (who was now strutting slowly away from the chick). It then darted about 2 feet towards the hen again, running under her body, between her legs, from behind. The hen again pecked at 103 the chick, and tossed i t away from herself, turning as she did so, and the same thing happened.about one minute later. Then the chick, after standing and calling loudly for several seconds, ran to area one, and stood quietly preening itself under the lamp. About 2 minutes later i t lay down, head on the ground, eyes closed, and remained thus for almost 2 1/2 hours. Occasion-ally i t shifted its position slightly, without getting onto its feet. This approach behaviour, from the chick to the hen, occurred over f i f t y times during the rest of the f i r s t day. On each occasion the chick was pecked viciously, and was clearly hurt. Blood appeared at the junction of its beak and "forehead", and the observer was strongly inclined to terminate the observa-tion. On some occasions the hen did not peck at the chick for about 10 seconds after i t ran under her, and, several times, the chick was stepped on by the hen as she turned. When the hen's foot released i t , the chick ran at least 2 feet from the hen, calling loudly, as i t had done while struggling under her foot. The hen did not jerk her foot up as soon as she stepped on the chick, but rather kept i t there for several seconds, with her weight on i t as she moved her other foot. The chick, after this, would stand, calling loudly as i t preened itself, for about half a minute, then would run or walk back to the lamp, soon to settle down beneath i t . When the observer left that night, the chick was lying under the lamp, with head down and eyes closed. The hen was sitting near the far corner of the pen,.facing away from the chick, eyes half closed, head pulled back into her body. The apparent hostility towards the chick (no anthropomorphism is intended) had been maintained whenever the chick approached. When the observer returned next morning, however, the hen was sitting in a corner near the lamp, with head up, clucking softly and intermittently. She looked upwards towards the obser-ver as he raised his head over the plywood walls. The chick was nowhere in sight. The observer checked with the staff of the poultry farm to find out whether anyone had removed the chick. No one had been in the room, and i t was subsequently discovered that the chick was underneath the hen. Occasionally the chick's movements could be inferred from the movement of the hen's body--and wing feathers. The hen would, occasionally, shuffle around slightly at which times the chick, or part of i t , might appear from under the hen, soon to disappear beneath her again. The hen clucked intermittently throughout the day, and occasionally pecked at the food scattered on the floor. The hen and chick stayed in this position through-out most of the day. Several times the chick came out, stretched, fluttered or walked about, pecked, defecated and looked a l l around, for a period of about 10-15 minutes. It then returned to 1 0 l f the hen. During the periods when the chick was out like this, the hen would bring its head down near the ground, stretching i t forwards, and watching the movements of the chick. It might also preen itself, and shuffle around a l i t t l e . Twice, during one of these periods, the hen stood up, ruffled her feathers, stretched her wings and neck, and walked forwards near the lamp. She spent about 1 5 minutes, mostly pecking from the large food dish, and also pecking into the large water dish, at the food on the ground, at her legs, and at the outer edge of the lampshade (metal). She defecated on each occasion and frequently clucked softly in extended bursts. After about 1 5 minutes she settled down in almost the same position as previously, and the chick soon returned to her. With the exception of these infrequent periods, the hen brooded the chick throughout the day. If there was a sudden disturbance, (someone opened the door, on one occasion, and spoke to the observer), the hen would show the previously described startle response, and would ruffle her t a i l feathers, shuffle slightly, with body raised a l i t t l e , and cluck loudly and irregularly until the disturbance ceased. She almost always looked towards the top of the plywood walls at these times, and in the direction of the disturbance. The observer could seldom raise his head over the walls without the hen being aware of his presence (she would cluck, shuffle about, and ruffle her feathers slightly). The chick hardly ever saw the observer— or, at least, paid almost no attention to him. The broody hens in the subsequent groups noticed the presence of the observer far less than did this hen, as they remained at the far end of the pen looking outwards, while this one remained (oh the second day) at the near end of the pen (where the observer usually was), looking inwards towards the lamp. When the observer spoke into the microphone, after remaining quiet for a short while, the hens would show a startle response pattern, but this usually ended within a few seconds, and the hens appeared unaffected by the observer's speech during most of the remainder of the time. ( 5 ) Group 2 / 0 ; two chicks with no broody hen. Both chicks were of the same species (White leghorn); the f i r s t to hatch (Chick A) was three hours old at the start of the observation period, the second one (B) was 6 0 to 9 0 minutes younger. A weighed **9 grams; B weighed M-6. The chicks' behaviour was generally comparable to that of the single chick in the fi r s t group, but was characterized by the following features: The two chicks behaved almost identically and simultan-eously. When one lay down, the other would li e down within a few seconds; when one stood up, the other would soon be standing, too; when both were lying, with head down and eyes closed, i f one 1 0 5 looked up, the other would act likewise. Although B appeared to be the f i r s t to act more often than A, quantitative analysis would probably show no significant difference. In addition to the preening and pecking movements found with the single chick, mutual preening and pecking were seen with this group. Sometimes, when one chick pecked the other, the second would not show any particular response, but often i t would run quickly to a new position, some inches away, calling moderately loudly. There was no clear-cut border between the more gentle and the more forceful pecks, nor between the degrees of response of the pecked chick. A great many of the pecks were directed towards the top of the other's beak, just forward of the eyes, and these almost always elicited the slight fleeing response described. The pair of chicks stayed extremely close together, especially on the f i r s t day—seldom more than about k inches apart, and mostly no more than one inch apart, or touching one another. When they were standing more or less s t i l l , or lying on the ground, one chick would often rest its beak and neck on the other's back and side. Another common form of contact consisted of one chick pushing its beak, head, and even body up to and under the other's body. If the latter chick were in a standing position, this would usually mean that i t would be pushed forwards, or to the side, and upwards—in which case i t would run forwards a few paces, upon landing, squawking moderately loudly, and then stand s t i l l again. If this chick had been lying at the time, i t would be pushed onto Its side and breast, and would usually stand up, move around, and settle down again against the side of the other chick. The chicks lay side by side, each against the other; almost invariably they lay under the lamp, and, like the single chick, they would mostly face away from the lamp, with their backs closer to i t than their heads. As they grew older, they became slightly more independent of each other (in a purely descriptive sense), both in the form and timing of current behaviour at any given moment, but i t should be stressed that this was only so to a slight degree. The distance between them tended to increase on the second day. Throughout the whole of the period of observation, this group spent less time lying on the ground under the lamp than did the single chick. They were active for longer periods and had shorter periods of inactivity than did the lone animal. It was the observer's impression that Chick B (the younger, lighter one) was more active and aggressive than A, and that i t lead A more often than i t was lead by the latter. (6) Group 2/1: two chicks with one broody hen. The chicks were both White leghorns, the hen was a White 1 0 6 Cornish cross. The younger chick (B) was one hour old, and the older one (A) two hours old, when observation began. They each weighed 5 0 grams. The behaviour of this group can well be des-cribed as being a combination of that observed in groups 2 / 0 and 1 / 1 . The group was more active than the f i r s t group ( 1 / 0 ) ; i t contained a l l the elements found in group 2 / 0 , as well as the approach behaviour of the chick to the hen observed in group 1 / 1 . There were the following differences, however: After the i n i t i a l encounters with the hen, and having been viciously pecked by her, the chicks spent far less time near the hen than did the chick in 1 / 1 . Thus, while the single chick in that group approached the hen at least f i f t y times during the fir s t day, these chicks approached their hen only eight times on the f i r s t day. Seven of these approaches occurred in the f i r s t five hours of observation, and the eighth about three hours later. After that, on neither the f i r s t nor the second day did the chicks ever come closer than 1 8 inches to the hen, who, like the former one, spent most of the time sitting at the far end of the pen from the chicks, looking away from them through the wire. These chicks did not settle under the hen during the night (at least, they were not under her the next morning), nor at any other time. They behaved dually as did the pair in group 2 / 0 . The observer could form no impression as to which, i f either, of the pair was the more strongly dominant; Chick A approached, and was pecked at by, the hen on two occasions more than Chick B. When they did approach the hen, they usually did so separately. One chick would remain about 1 8 inches from her, watching her and the other chick. This other one would move towards the hen's legs, from the side and rear.(the hen would stand whenever the chicks came within about 2 feet of her). If the hen did not attack the chick immediately, the other one would follow i t within a few seconds, when they would both be pecked at by the hen. If she tossed one of them away., the other ran from beneath the hen towards i t , and stood near i t . If the hen did attack the f i r s t chick when i t f i r s t approached, the second chick would stay where i t was, away from the hen, or move towards the fi r s t chick. They did not immediately return to the lamp, but spent several minutes walking, standing, looking around, preening (especially the one that had been tossed by the hen)", and pecking. They then, at f i r s t at least, approached the hen again, but later, spent less, time near the hen after being attacked. Chick A bled slightly at the top of its beak after several attacks by the hen, and throughout the rest of the obser-vation Bpeeked at this area. A would run from B when this 1 0 7 happened, calling loudly and continuously for about 1 0 seconds. They would soon be next to each other once more, either of them approaching the other, or both approaching simultaneously. ( 7 ) Group VO: three chicks with no broody hen This was a mixed group, containing two New Hampshire's, and one White Leghorn. Chick A, a New Hampshire, was 3 1 / 2 hours old, Chick B, the White Leghorn, was 2 1 / 2 hours old, and Chick G, the other New Hampshire, was about one hour old, at the start of the. observation. Chicks A and B weighed *+9 and k8 grams respectively, and Chick C weighed 5 1 grams. The behaviour of the chicks in this group contained no new items; i t was characterized, however, by a somewhat different orientation than that of the previous groups, as follows: When the three chicks were placed under the lamp, one of them (C) lay down almost immediately, and its head went onto the ground, with eyes closed, about 2 0 seconds later. A and B, however, walked around close together under the lamp for just less than 5 minutes. They looked a l l around, especially at each other, and pecked at the ground several times in this period. Chick B shook itself violently at one stage, almost toppling over, whereupon A ran forward away from i t , about 6 paces. A quickly rejoined B. When they lay down, they did so side by side, about h inches from C. Throughout the rest of the observation period, A and B acted as a pair (like the chicks in 2 / 0 ) , while C remained relatively independent of them—this was by no means an absolute affair, however, for C would sometimes be close to the others and act as they were acting. Mostly, though, either A or B, or both, would run at and/or peck at C when i t came within about 3 inches of them. In addition to this, A and B would often be showing one form of behaviour, while C would act differently. When a l l three were lying under the lamp, G would almost always be close to or touching either or both A and B, who usually lay down after C. It was when the three of them were not lying under the lamp that the subgro.uping became far more noticeable. Chick C spent far more time lying under the lamp than did A or B—often these two would be down after C had done so, and. would rise while C remained lying on the ground. A and B, the more active members of the group, were somewhat less active than either the two chicks in group 2 / 0 , or those in 2 / 1 . ( 8 ) Group 3 / 1 : three chicks with one broody hen. Three New Hampshire chicks and one White Cornish crossed formed this group. Chick A, at the start of the observation, was 1 0 8 k 1 / 2 hours old, and weighed *+6 grams; B was about 2 hours old and weighed the same; C was also about 2 hours old, and weighed W3 grams. This group did not exhibit the same division between its members as did the previous one. Although the chicks did form themselves into a pair and an individual on many occasions, the members of the pair were not always the same, nor did they oppose the intrusion of the third chick (again, this phrase is used descriptively only), and, indeed, these chicks were often found in a trio. Their approaches to the hen were similar to those of the chicks in group 2 / 0 , except that two chicks would usually approach her more or less at the same time, while one would stand some 1 8 inches away. Sometimes one would approach alone, and at other times, a l l three chicks moved towards her together. Chick B received the greatest number of pecks from the hen, which is related, no doubt, to the fact that i t was this chick which approached the hen more often. B approached the hen about 1 0 times on the fi r s t day, and once the second day, while A and C approached her seven times, on the f i r s t day only. If two chicks had approached and been attacked by the hen, the third chick would run towards them, whereas, i f one chick had approached by itself, i t would run to the other two when i t had regained balance. The hen behaved much as the other hens had done, except that, when the observer arrived on the second day, she was sitting much closer to the lamp than the others had been, and closer than she was on the previous evening. She sat about 2 feet from the lamp at this time (the chicks were underneath it ) and she settled on this spot whenever she was not moving about on the second day (i.e., she sat here most of the time). ( 9 ) Group k/Qi four chicks with no broody hen. This group contained four New Hampshire chicks. A was 5 hours old and weighed k9 grams; B was 3 1 / 2 hours old and weighed *+8 grams; C was 3 1 / 2 hours old and weighed grams, and D was 2 1 / 2 hours old and weighed *+9 grams, at the start of the observation. B was indiscriminable from G, and was identified, therefore, by means of a small piece of white paper, fastened to the middle of its back with adhesive tape. This was done just before the chicks were placed in the observation pen—it did not appear to have any effect upon the chick's behaviour; the chick did not peck at i t or preen in that area, which i t could easily have done. 109 The chicks acted more or less as a single group—they did the same things at roughly the same time. They sometimes split into two pairs, but never remained in two groups of 3 and 1 for more than a few seconds—the fourth chick would quickly run (usually) or walk to the others. They showed the mutual preening and pecking as did the other dual and plural groups, as well as the forms of behaviour described in connection with the single chick. Chick B was probably the most active/aggressive/dominant, and Chick D probably the least so (it remained under the lamp somewhat longer than the others on many occasions), but this is the expression of but a mild impression. This group was the most active of a l l the groups. The chicks spent only short periods lying beneath the lamp, never more than twenty minutes at a time, and usually less than this, whereas the least active group (the single chick in group 1/0) spent periods of up to an hour or more lying there. In addition to this greater activity, these chicks also ventured to the far walls of the pen more frequently than did any of the others, indeed, this was the only group which went to the farthest corner from the lamp (except when chicks, in other groups, approached the hen in that corner). (10) Group M-/1: four chicks with one broody hen. This group contained four White Leghorn chicks in addition to the White Cornish crossed hen. The chicks 1 statis-tics, at the start of the observation period were as follows: Chick A was k hours old and weighed h7 grams; Chick B was 3 hours old and weighed^k8 grams; Chicks C and D were about 1.1/2 hours old and each weighed ^6 grams. These chicks formed into pairs when they stood up, after spending about 10 minutes (until the arrival of the hen) lying under the lamp. They watched the arrival of the hen, moving around occasionally beneath the lamp. As the hen strutted quickly to the far end of the pen, Chick C ran about on one foot, in very jerky fashion, towards her but stayed there while the hen continued another 3 feet or so. Chick D slowly walked towards C, who moved back towards the lamp. C and D stood in area two for several minutes, close together, and looking towards the ground, pecking occasionally, and looking towards the hen. A and B, meanwhile, remained beneath the lamp, looking towards the hen and towards the two chicks ahead, moving around in this area, and occasionally pecking towards the ground. Thereafter A and B, and C and D formed into two respective pairs during most of the time when they were not lying beneath the lamp (at which time they lay in one bunch). The members of one pair did not, however, peck at the members of the other i f the latter approached them, and often a l l four would move as a single group—but, as in group V o , the chicks never 110 formed i n t o groups of 3 and 1 , or never stayed t h a t way f o r more than a few seconds. In t h i s case, however, the s i n g l e c h i c k would u s u a l l y not run to j o i n the t h r e e , but r a t h e r , one of the others (almost i n v a r i a b l y i t s more constant companion) would run or walk out to j o i n i t , and. the group would continue as two p a i r s immediately f o l l o w i n g t h i s . A and B, as a p a i r , approached the hen about twice as o f t e n as d i d G and D. A approached her eig h t times, B d i d so ten times, w h i l e C and D d i d so f i v e times each. The l a t t e r two c h i c k s watched the former ones whenever they approached the hen, standing about 1 8 inches from her. On s e v e r a l occasions, three c h i c k s approached, wh i l e one remained d i s t a n t , but only once d i d a l l f o u r c h i c k s move i n together. U s u a l l y , two approached while two stood apart. None of the c h i c k s approached the hen on the second day. B. IN THE IMPRINTING SITUATION ( 1 ) FIRST EXPOSURES Chick No. 1 . approximate age = h hours. When E r a i s e d the l i d of S's box, S looked up and around. As E ! s hand approached, S stood up. As E l i f t e d S o f f the f l o o r , S gave few loud sharp c a l l s , and struggled w i t h i't s i whole body f o r a moment—moving backwards, i n so doing, towards E's w r i s t . S e t t l e d down i n E's hand. E placed h i s other hand, i n cupped f a s h i o n , over the hand h o l d i n g S. S q u i e t as c a r r i e d i n t h i s f a s h i o n to runway. Few loud c h i r p s as S was l i f t e d over the w a l l s of runway and placed on f l o o r (E used only one hand i n doing t h i s ) . Immediately s e t t l e d on f l o o r , head medium h i g h , body c o l l a p s e d on ground, eyes open, and head f l i c k i n g around s l i g h t l y — no sound from S f o r approximately 1 0 seconds. Then waddles/ f l u t t e r s to the l e f t about 6 i n c h e s , w i t h head up and c a l l i n g l o u d l y . S e t t l e s as before, but w i t h head much higher and s t i l l c a l l i n g l o u d l y . A f t e r about 1 1 / 2 minutes f l u t t e r s / w a d d l e s f o r -ward, as before, s t i l l calling---about 1 8 inches. S e t t l e d f o r 2 minutes, head f l i c k i n g / j e r k i n g around, o c c a s i o n a l s h i f t of body p o s i t i o n , q u i e t . Then f l u t t e r s forward, as before, and i n s e v e r a l d i r e c t i o n s , c a l l i n g l o u d l y . [The c a l l s were timed, approximately, as f o l l o w s : k or 5 c a l l s i n 2 seconds; r e s t , of between 1 1 / 2 and 3 seconds; then repeated s e v e r a l times. They were not always so r e g u l a r , however—there would, sometimes be up to 1 2 c a l l s i n r a p i d succession, w i t h some slower ones towards the end of the b u r s t . ] I l l S e t t l e s down near wall, head up, c a l l i n g loudly. Waddles forward against the wall. About every 1 0 seconds, waddles/flutters along or near wall (using wings, as i t moves, with jerky f l u t t e r i n g action). Galling almost continuously i n irr e g u l a r bursts. SOUND ON: No noticeable difference i n chick's behaviour. C a l l i n g continued as above, with occasional pauses of up to 5 seconds. Stays mostly i n same posi t i o n , body collapsed, feet underneath, head medium high, head ofien moving around i n small jerks, feet/body s h i f t i n g s l i g h t l y on occasion. Loud c a l l i n g continues almost the whole time, sometimes with a few lower-pitched rougher notes, and i n t e n s i t y may vary. Remains near wall (about 1 inch from i t ) during t h i s time. MOVEMENT ON: S watches target-object (T.O.) approaching when T.O. i s approximately 1 8 inches away, stopped c a l l i n g as i t watched. As T.O. passed S, S f l u t t e r e d forward almost to i t , pecked at side of T.O. twice, watched i t depart, f l u t t e r e d forward i n same d i r e c t i o n f o r about 8 inches, s e t t l e d , body down, watched i t move another foot or so, then looked around i n several d i r e c t i o n s , c a l l i n g s t a r t s again (had remained quiet since f i r s t seeing T.O. u n t i l now). As T.O. approaches again, S runs to i t while i t i s s t i l l about one foot away, pecks at i t , turns body around with T.O. as i t passes, moves with i t , then just behind i t , f o r about 3 feet. Stops, watches i t depart, then looks around i n several d i r e c t i o n s , head stretched up, body f l a t on ground, c a l l i n g loudly u n t i l i t returns. As soon as S starts to run towards T.O., c a l l i n g ceases, and does not s t a r t again u n t i l S stops following and watching T.O. Subsequent behaviour was very similar to the above throughout the res t of t h i s period (sound on, movement on), with sometimes the following v a r i a t i o n s : After i t had pecked at T.O., as i t was passing, S would occasionally peck at the ground once or twice, then r a i s i n g head to medium height (beak h o r i z o n t a l ) , would chobble f o r a moment. Then i t would f l u t t e r quickly forward a f t e r the T.O. By about 5 minutes of t h i s period, c a l l i n g had ceased almost e n t i r e l y , and S would l a y head down near or on the f l o o r i n front of i t s body, i n the i n t e r v a l between the approaches of the T.O. 1 1 2 It would often peck two or three times at the shavings on the floor, and chobble immediately afterwards. Whenever T.O. approached within about one foot, S's head would come up, and its eyes would open wide (when head was on or near floor, eyes would often be closed, or partly closed). S would flutter towards T.O. (lying in T.O.'s approach line) no more than about 3 inches. As T.O. struck and rolled over S's body, S would usually peck once or twice at i t . Following was now much shorter, S usually waddles slowly behind T.O. for about 6 inches, and would then watch i t for another 2 feet. At around 8 minutes of this period S looked up at approaching T.O. and ran half the length of the pen to i t , chirping softly, turned, followed closely and continuously for 1 8 inches, then settled . down, watched T.O. depart, then head down on floor as well. Thereafter following persists for much longer than before, lasting up to *f feet as the T.O. departs, and being preceded by S approaching T.O. with a rapid fluttering movement (using wings). There was no occasion on which S did not make some response to the approach of the T.O., even when S's head .was on the floor and its eyes apparently closed. At the very least, S would raise head, watch T.O. approach, waddle or flutter towards i t a few inches, turn with i t , and watch i t depart. SOUND OFF: No noticeable change in S's behaviour. MOVEMENT OFF: S was lying, with head down and eyes closed at the time. Remained so for 2 0 seconds, then looked up, head high, stood up, 6 loud calls as i t looked around. Ran to T.O. which was swaying from side to side, about k feet from chick. Quiet. Pecked twice at T.O., then moved around i t , with body touching i t , pecking at floor. Moved about 3 inches from T.O., s t i l l pecking at floor, settled down on ground, head low, chobbling and further pecking. Chick No. 2 . approximate age = 1 1 / 2 hours. Behaviour when being taken from box to runway etc. was comparable to that of the f i r s t chick. Immediately settled quietly in runway, head at medium height (beak horizontal). Remained quiet for 3 0 seconds, then gives few soft calls, head low but looking around, calls become increasingly loud. Moves after 3 minutes, turning body around, but not progressing. Head moving around most of the time, calls very loud now, bursts of about 8 in k seconds, then pause of between 2 and 8 seconds. 1 1 3 Quiet and f a i r l y s t i l l i n l a s t minute before: SOUND ON: Remains quiet, head jerks up when sound comes on, gradually sinks lower again j sinks down to ground within 2 0 seconds, eyes apparently closed, quiet. Remains thus u n t i l : MOVEMENT ON: T.O. almost h i t s S's beak; eyes open, turns head as T.O. passes, turns body, watches T.O. depart. Stretches neck up high, few soft chirps, walks slowly forward (waddles) four paces (T.O. now at end of runway). Body sinks to ground, head medium height, looking slowly around. Watches T.O. approach from 2 feet away, few soft chirps, turns head and body" as T.O. passes, watches T.O. depart, waddles 3 paces forward (T.O. 1 foot ahead), pecks, chobbles, few soft chirps, body on ground, head low. T.O. approaches again, S watches, watches T.O. pass, does not turn head or body to watch i t depart. Head sinks down, eyes h a l f closed, jerks head up again before i t has sunk to f l o o r , eyes open wide, pecks several times, chobbles, an occasional chirp. Next time around, S waddles slowly towards approaching T.O., 2 1 / 2 feet away, turns head and body as i t passes, watches i t depart. Ides down, chobbles, head very low, few occasional soft chirps. Next time around, S pays no attention to T.O., but remains with body f l a t , head low, eyes apparently closed, just outside l i n e of moving T.O. An occasional chobble and chirp. Thereafter S remained l i k e t h i s f o r most of the time. It would usually look up as T.O. passed close by i t , and would turn head s l i g h t l y , but quite often i t paid no attention to T.O. Head would also come up sometimes when T.O. was not near S, would peck and chobble, and sometimes chirp s o f t l y , a few times. SOUND OFF: No change i n chick's behaviour observed. MOVEMENT OFF: Remained l y i n g s t i l l , head on ground, eyes closed, f o r 1 5 seconds, then jerked head up, eyes open, looked around, gaped 111+ twice, head sank down towards ground again (very slowly), s h i f t e d position of legs underneath i t s body, head sinks onto ground. Chick Mo. 3. approximate age = 5 hours. Behaviour, when being transported to runway, was similar to that of the f i r s t chick. When placed i n runway, stands, head up, looking around, loud c a l l s within 5 seconds—these continue u n t i l the sound comes on (see below). Runs/flutters forward a f t e r 1 1 / 2 minutes (quiet f o r a few seconds during and af t e r t h i s ) , stands, looks around, as before. Ran forward again about 6 paces after-further 3 0 seconds (quiet while running and f o r few seconds afterwards). Stands, head moving around, f o r about 2 minutes, then runs forwards again (another short quiet period). Stands, head moving around just above the f l o o r , then higher, loud c a l l i n g continues. SOUND ON: Stops c a l l i n g immediately,, stands ( s l i g h t l y down on haunches) head s t i l l , stretched out short way straight i n fro n t of body, beak just below horiz o n t a l . Remains thus f o r r e s t of th i s period. MOVEMENT ON: The T.O. came up from behind, without S seeing i t , i t h i t the side of h i s body. Gives a very long loud cry and runs quickly to the wall (about 1 f o o t ) , using wings, and head and body low. Stands s t i l l , watches T.O., few loud c a l l s , but mostly quiet, preens l e f t foot vigourously, pecks at ground three times. A similar pattern of behaviour was observed on the next two occasions on which T.O. passed near S. On the fourth time around, S stands with head up, watches T.O. as i t approaches, passes, and departs. No c a l l s given. Pecks at ground, head comes back up, looks around i n several d i r e c t i o n s , moves slowly forward a few paces. On the f i f t h time around, S watches T.O. approach and pass. He runs/ f l u t t e r s towards i t when i t i s 1 8 inches past him, stops 6 inches behind i t , quiet the whole time. Stands there, head turning around j e r k i l y , some soft chirping. On the sixth occasion, S watches T.O. as i t passes him and follows ( f l u t t e r s f a i r l y quickly) f o r one foot, when i t i s one foot away. 1 1 5 Next time, S looks and runs towards T.O. when i t is s t i l l k feet away, pecks at i t as i t passes, turning with i t , does not move after i t . Moves around in same position, head low, pecks twice at ground, head up, chobbling, quiet. S pays no attention to T.O. when i t next passes near him, is sitting down now, body flat, head low, quiet, facing a side wall. The next time, S moves in towards i t as i t passes, and pecks at i t , turning with i t . Watches i t depart for 18 inches, runs forward four paces, stands, looking a l l around. The tenth time the T.O. passed, S watched i t until i t was near the far end of the runway, then ran the whole length of the runway, followed i t around the pulley, pecking at i t as S followed. Stops, head goes down to ground, pecks several times. The next time around, S watched approach of T.O., ran towards i t for 6 inches when i t was one foot away, lies down, head almost on the ground. Thereafter S remained lying in the same position, quiet, head on the ground. When T.O. passed, S's head would come up, with eyes open, but after about five seconds, head would sink quickly down again. On two consecutive occasions S appeared not to notice the T.O. as i t passed. SOUND OFF: No change in S's behaviour. MOVEMENT OFF: No change in S's behaviour. Head moved slowly up off the ground, eyes s t i l l apparently closed, and sank back down again slowly within a few seconds, after about k$ seconds of this condition. Chick No. k. approximatelage = h hours. Behaviour similar to that of fi r s t chick, before being placed in runway. Stood, head up, looking around, extremely loud calls within 5 seconds, shifts legs several times, hardly moving. Remains like this until: 1 1 6 SOUND ON: Stops calling, goes down on haunches (body just clear of ground), head pulled into body, beak above horizontal. MOVEMENT ON: "The T.O. passed him at about 3 inches distance, S appeared not to notice i t . He waddled towards centre of runway, with back to T.O., when T.O. was at far end. T.O. rolled over his body, S turned head towards i t , gave single, moderately loud chirp, watched i t depart. The next two occasions were similar to this. The fif t h time T.O. passed, S watched i t pass him, then walked after i t for 5 paces, staying very close to i t . Then S stood, quiet, pecking, moving around slightly most of the time. The next time, S was pecking at ground when T.O. came near—S appeared not to see i t , continuing to peck. The subsequent passing was the same as this. Then S looked up at T.O. as i t next passed, walked after i t for one foot, staying about 6 inches behind i t . Stopped, watched i t depart, pecked at ground several times, turned, stretched whole body, fluttering wings, pecking again. When T.O. next approached, S turned with i t and watch^ ed i t depart, then body sank to floor, eyes slowly closing and head slowly dropping towards the ground in front of S's body. Remained so until T.O. was near (2 feet) again, when walked towards i t , turned with i t , stood watching i t depart. Settled on ground again, chobbling as i t went down. Thereafter, S remained with body on the ground for most of the time, with head on of near the ground, and eyes at least partly closed. Oh every subsequent occasion, except three, when T.O. approached, S's head would come up, and eyes would open for few seconds as i t passed, then head would sink back onto ground again, with eyes closing, before T.O. was one foot away. Occasionally S shifted legs slightly under it s body. SOUND OFF: No change in S's behaviour. MOVEMENT OFF: No change for kO seconds, then S ran quickly forward, away from T.O. (which had been *t feet away), settled down again, with two soft chirps. 1 1 7 Chick No. 5 ; approximate age = 3 1/2 hours. I n i t i a l behaviour the same as with the f i r s t chick. Squatted (on haunches) In runway, head moving s l i g h t l y , soft chirps within 5 seconds, lasted 3 0 seconds. Then quit f o r 3 0 seconds. Then short bursts of5 6 to 8 moderately loud c a l l s , with i n t e r v a l between bursts of about 1 5 seconds. This changed to long bursts of louder c a l l s , about 1 5 c a l l s i n each burst, with i n t e r v a l s between the bursts of about 3 seconds. SOUND ON: Immediately quiet. Remained i n same po s i t i o n , head s t i l l , beak ho r i z o n t a l , few soft chirps during the two minutes. MOVEMENT ON: The T.O. struck S's body, before S saw i t . Ran f l u t t e r i n g away, very loud c a l l s , to side of runway. As i t approached again, S ran ahead of i t along wa l l , with loud c a l l s . Stopped at end of runway," watched as T.O. caught up, s t i l l c a l l i n g loudly, ran back along runway when T.O. about 6 inches distance, loud c a l l s as i t ran. The same thing happened on the next two occasions when T.O. came near S. Then, as T.O. caught up with S again, S turned back towards i t , and stopped c a l l i n g as i t passed. The next f i v e times T.O. approached, S gave several loud c a l l s as i t came near, then was quiet as i t passed and departed—S watched i t during t h i s time. For the next two occasions, S remained quiet the whole time, pecking at the ground in t e r m i t t e n t l y , body sank to ground, head sank towards ground, eyes closing at the same time. Paid no attention to T.O. The time aft e r t h i s , S looked up, watched T.O. pass, stood up, walked behind i t f o r four paces, stood watching i t depart, then pecked, turned around, looked i n opposite d i r e c t i o n , with an occasional soft chirp. Then the T.O. h i t S on the side before S saw i t . S turned quickly around, no c a l l i n g , watched T.O. depart, and walked 7 paces aft e r i t . Pecked several times, standing s t i l l , then ran towards T.O. as i t went around the pulley wheel. Thereafter S usually stood pecking, looking around with head low, occasionally s h i f t i n g position. When T.O. approached, S would watch i t turn with i t , watch i t depart for about a foot, then walk 6 paces or so af t e r i t , and resume pecking etc. S remained quiet the whole time. 118 SOUND OFF: No immediate change i n S's behaviour. Then gave a few soft chirps as T.O. departed. After that, S ran behind and past T.O. f o r about h a l f the length of the runway, stood, pecked at ground. When T.O. had gone farther away, S gave many loud c a l l s , became quiet when i t was near. This continued u n t i l : MOVEMENT OFF: S was just behind T.O. at the time. S stood s t i l l , watching T.O., then body collapsed onto ground, head sinking down, eyes clo s i n g . Chick No. 6; approximate age = 6 hours. I n i t i a l behaviour similar to that of f i r s t chick. Stood qu i e t l y i n runway f o r 5 seconds, then very loud c a l l i n g , ran to side wall, then along t h i s wall and back, c a l l i n g loudly the whole time,and moving f o r most of the time (occasional pauses of. about 5 seconds, when S would stand facing wall, head up, and jerking s l i g h t l y ) . SOUND ON: Stood quietly f o r 10 seconds, head up, s t i l l , then began running again, about 1 inch from the side w a l l , and across the end walls, about 6 inches from them, c a l l i n g loudly almost the whole time. MOVEMENT ON: No change i n behaviour f o r about k minutes, paid no attention to T.O. Sometimes ran i n same d i r e c t i o n as i t , sometimes i n opposite d i r e c t i o n , sometimes towards i t , sometimes away from i t , sometimes passed i t at the ends of the runway, sometimes i n the middle. Loud c a l l s most of the time. Then S suddenly stopped c a l l i n g as T.O. approached, watched i t pass him, then started c a l l i n g loudly again when i t was 2 feet past him. The same thing happened the next time around. The following time, however, S ran afte r T.O. f o r 2 complete c i r c u i t s , almost without pausing. S would run up to T.O., and place the side of his head against i t . S would then stand and watch T.O. u n t i l i t was about 1 foot ahead again, when he would repeat t h i s procedure. S occasionally pecked at the ground i n between the runs to T.O. S c a l l e d loudly, but le s s often than before, during a l l t h i s time, both when running and when standing watching T.O. After t h i s S stood i n one corner of the runway, looking towards the walls, c a l l i n g loudly, paying no attention to the T.O. 119 When i t had passed him several times, S turned, as i t passed again, watched i t , then ran afte r i t f o r 2 fee t , c a l l i n g loudly, and stopping about 6 inches i n front of i t . When T.O. passed him again, S ran up to and i n front of i t again, s t i l l c a l l i n g most of the time. Then S watched T.O. depart. SOUND OFF: S stood quietly f o r 15 seconds, watched T.O. pass, ran across to wall, c a l l i n g loudly. Ran along the wall , s t i l l c a l l i n g . Stopped and watched T.O. several times, when i t was moving near him, but did not follow i t . Was quiet at these times, then resumed c a l l i n g and running around the walls. MOVEMENT OFF: Continued loud c a l l s as ran around walls. Paid no attention to T.O. which was swaying near one corner; passed close to i t several times. Chick No. 7; approximate age = 3 hours. I n i t i a l behaviour similar to that of f i r s t chick. Squats on haunches i n runway, quiet f o r about 5 seconds, then begins c a l l i n g loudly and almost continuously. Stays thus u n t i l : -SOUND ON: Stays squatting as before, c a l l i n g stops f o r 10 seconds, then intermittent short bursts of loud c a l l s u n t i l : MOVEMENT ON: As T.O. approached, S watched i t . When T.O. was 2 feet away, S started c a l l i n g loudly. As i t passed him, S became quiet, turned with i t , watched i t depart. Remained quiet. Settled down, body f l a t , head low and almost s t i l l , eyes open. On each of the next three occasions, the T.O. r o l l e d over the top of S's body. S remained quiet both before and after T.O. passed, and did not look up at i t . The next time around. S watched approaching T.O., and turned head and body ( s l i g h t l y ) as i t passed, then turned head r i g h t around the other way, past the front of i t s body, and watched T.O. depart. 1 2 0 Next time, S looked up as T.O. passed, and watched i t depart. This happened on the two subsequent occasions also. Then, when T.O. was at f a r end of runway, S gave several loud c a l l s . As i t approached to within 3 feet of him, S became quiet, watched i t pass and depart, turning both head and body. S then moved across to a side wall (the f i r s t time S has moved forward), pecked several times at the ground, squats on haunches, facing wall, occasional soft chirp. Does not respond to T.O. the next three times i t passed.near him. Then turns towards i t as i t approaches, watches i t pass and depart. Head sinks down to ground, body f l a t on ground, eyes h a l f closed. Pays no further attention to T.O. SOUND OFF: Remains quiet and i n same po s i t i o n , but head comes up, turns i n several d i r e c t i o n s . As T.O. passes him, S watches i t turning only h i s head, except on two occasions when he turned his body as well. MOVEMENT OFF: Remains quiet f o r 1 0 seconds, then extremely loud c a l l s , runs across to opposite wall, stands, quiet f o r 1 5 seconds, c a l l s loudly again, head high, looking around. Runs along side wall f o r •«+ f e e t , c a l l i n g loudly. Lies down about 2 inches from swaying T.O., head near ground, eyes h a l f closed, quiet. Chick No. 8; approximate age = 5 hours. I n i t i a l behaviour similar to that of f i r s t chick. Squats q u i e t l y . i n runway f o r about 5 seconds, then soft c a l l i n g , becoming louder. Stands up after 3 0 seconds, very loud c a l l i n g . Runs i n short burst around most of runway, c a l l i n g loudly. This continues u n t i l : SOUND ON: No change apparent. The pauses i n S's running, and i n his c a l l i n g , do not coincide. MOVEMENT ON: The f i r s t s i x times T.O. passed near S, he appeared not to notice i t — h i s -behaviour continued with no change from the above manner. On the seventh, eighth, ninth, and thirteenth 1 2 1 occasions that the T.O.: passed him, S turned head and watched i t (standing s t i l l ) . Apart from that h i s behaviour remained unchanged—as he watched the T.O., S continued c a l l i n g loudly. As the T.O. passed him f o r the f i f t e e n t h time, S peckedafcjttwice, then stood and pecked at the ground, without c a l l i n g . Squatted on haunches f o r about 1 5 seconds, then stood up, began c a l l i n g loudly again, and resumed h i s running i n short bursts. This continued u n t i l the T.O. stopped moving (see below). SOUND OFF: No change. MOVEMENT OFF: S t i l l c a l l i n g loudly and running about. Runs to T.O. (swaying at one end), pressed side of head, neck, and breast against i t , then pecked at i t three times. Quiet as soon as he reached T.O. Pecks at i t several times more, as i t sways i n front of him. Presses body towards T.O., does not move as i t str i k e s him. After 5 0 seconds, runs to the other end of the pen, stands there q u i e t l y , looking at wall. Chick No. 9: approximate;.age = k 1/2 hours I n i t i a l behaviour similar to that of the f i r s t chick. When placed i n runway, squatted on haunches, body just off the ground. Quiet f o r few seconds, then soft c a l l i n g , becoming quickly much louder. Remains thus f o r most of the time, with an occasional run (6 i n the five-minute period) forwards about one foot, when squats again. Loud c a l l s continue both when S moving and s t i l l . SOUND ON: No change—S runs forward, about one foot, three more times i n t h i s period. MOVEMENT ON: As the T.O. approached f o r the f i r s t time, S ran towards i t . I t h i t him as i t passed. As he ran to i t S was quiet, and he remained so as he turned and watched i t depart. Loud c a l l i n g resumed when T.O. was about three feet past S. He ran about near one side wall i n the middle of the runway, ignoring the approaching T.O. This continued on four more occasions. As the T.O. passed S, after t h i s , i t struck h i s body. S turned and watched i t depart, c a l l i n g ceased. He then 1 2 2 ran after i t when i t was 2 feet away, stopped i n front of i t , watched i t pass again, ran after i t again. Few soft chirps i n th i s time. Loud chirps as T.O. moved to other end of runway, quiet as i t returned (S ran towards i t ) . For the rest of t h i s period, S usually watched the T.O. as i t approached him, about 2 to 3 feet ahead of him, then turned as i t passed, and watched i t depart f o r about 2 f e e t , when he would run either up to i t , or just behind i t , stop and watch i t pass him again, and then run up to i t again. During t h i s time, 23 was mostly quiet, with an occasional soft chirp or two. SOUND OFF: Behaviour as before. MOVEMENT OFF: S was 3 1 / 2 feet away from T.O. at the time; S stood, head up, quiet, looking around. Then started c a l l i n g loudly a f t e r 1 0 seconds, ran across runway away from T.O. Stands, c a l l i n g loudly, head turning i n several d i r e c t i o n s , including towards the T.O., some six feet away. Chick No. 1 0 ; approximate age = 3 hours. I n i t i a l behaviour similar to that of the f i r s t chick. Squats i n runway, quiet f o r 3 5 seconds, then stands up, s o f t l y c a l l i n g , then more loudly. Short bursts of running around runway for about one foot, then long pause (squatting) u n t i l next burst. C a l l i n g loudly almost continuously. SOUND ON: No change i n S's behaviour. MOVEMENT ON: As T.O. passed S, i t struck h i s beak. S gave a sharp loud chirp, shook h i s head, and stood s t i l l . Stood i n same spot, c a l l i n g loudly, u n t i l T.O. approached a g a i n — j u s t before i t passed him, S began pecking at the ground. The T.O. passed over S's lowered head—S made no apparent response to i t , but continued pecking, with bursts of loud c a l l i n g between most pecks. The t h i r d time T.O. approached, S looked towards i t , and turned h i s head (not h i s body) as i t passed. He was s t i l l c a l l i n g loudly. 123 As T.O. approached next time, S stopped c a l l i n g , moved towards i t (6 inches away), turned h i s head and body, and watched i t depart. The next time, S ran towards T.O., one foot away, turned and pecked at i t as i t passed. On the sixth occasion, S watched i t pass him, then ran aft e r i t f o r one foot, when i t was 2 feet away. He then watched i t depart again, and preened behind h i s l e f t wing. The next time around, 8 ran af t e r i t , looking away to the side, i n the d i r e c t i o n of one wall. Stopped just behind T.O., pecked at ground several times, and gave a few soft chirps. On the next two occasions, S was pecking at the ground, walking about s l i g h t l y , with head low—he paid no attention to the T.O. The tenth time i t passed, S ran towards i t (2 feet away), turned with i t , and watched i t depart. He ran after i t when i t was one foot away. Stopped on reaching i t , pecked at the ground, ran afte r i t when i t had moved a farther 2 f e e t , and stopped s i x inches behind i t . Stood looking a l l around, s t i l l quiet. The next time, S ran to the T.O. (2 1/2 feet away) pecked at i t , did not turn and follow. Pecked at the ground several times. S was looking towards the wall when the T.O. next passed—he made no response. As he stood i n t h i s p o s i t i o n , S gave a few soft chirps. Then S ran to the approaching T.O. (1 foot away), pecked at i t as he turned with i t , and watched i t depart. Pecked at the ground. After t h i s , S ran to i t when i t was 2 feet away, then stood, pecking at the ground. Few soft chirps. S did not turn and follow. Thereafter, S ran to the T.O. when i t was about 2 feet away, turned with i t (sometimes pecking at i t ) , watched i t depart, then stood looking around, or pecking at the ground, moving h i s feet s l i g h t l y , and remaining quiet. SOUND OFF: When T.O. next approached S, he ran to i t (1 foot away), turned with i t , watched i t depart f o r one foot then ran af t e r i t , 12h and followed i t steadily for about k feet, some 1 0 inches behind i t . Then S stood s t i l l , head moving a l l around, pecked at the ground for the rest of this period, paying no further attention to the T.O., but moving around, with head low.. MOVEMENT OFF: S stood watching swaying T.O.., about 3 1/2 feet from i t . After 1 0 seconds S ran to i t , stood pecking at i t , then walked slowly and jerkily around i t , and pecked at the ground several times. S then pecked at T.O. several times more, then at the ground again. Chick No. 1 1 ; approximate age = 6 hours. Initial behaviour similar to that of the f i r s t chick. In the runway, S stood s t i l l and quiet for 1 5 seconds, with head at medium height (beak horizontal and pointing directly forward). Then S moved forward 3 paces, and gave a few soft chirps. The chirping became louder and much more frequent. S moved around on the same spot, head moving a l l around (in-cluding up and down) continuously. SOUND ON: Quiet for 1 0 seconds, then loud calling and looking around, as before. MOVEMENT ON: As soon as T.O. approached, S stopped calling, and did not call again during the whole session. S watched T.O. approach, pass, and depart, turning his body as T.O; passed. S watched T.O. as i t moved a l l the way down to the end of the runway and back again. S pecked T.O. as i t passed for the second time, turning with i t , then pecked at ground and chobbled. Subsequent behaviour in this period was similar to that above: whenever T.O. approached, S looked towards i t , usually turning with i t and watching i t depart. When i t had passed, he pecked at the ground, moving about in the same area, with head low. Occasionally S would peck at the T.O. as i t passed. He raised his left foot towards his beak on one occasion (T.O. at far end) and pecked at i t , almost losing balance. S did not move from the immediate area until: SOUND OFF: T.O. approached, S turned with i t and followed i t around a complete circuit, staying within 6 inches of i t , and 1 2 5 behind i t a l l the way. Then S pecked at the ground u n t i l T.O. approached again, when he followed i t f o r one length of the runway. Then he stood looking about, or moving around, pecking, paying no further attention to T.O. u n t i l : MOVEMENT OFF: S stood watching T.O. f o r 5 seconds, as i t swayed. Then ran up to i t , pecked at i t , pecked underneath i t , and at the ground, around i t . He moved around the T.O., pecking i n t h i s fashion. Chick No. 12; approximate age = 3 hours. I n i t i a l behaviour similar to that of f i r s t chick. In the runway S lay with body on the ground, head at medium height, looking around—quiet f o r approximately 10 seconds, then a few soft chirps. These became much louder within a few seconds. S stands up, head high, c a l l i n g loudly af t e r 1/2 minute. One and a h a l f minutes l a t e r i t l i e s down again, stops c a l l i n g , head at medium height, looking a l l around. Remains thus u n t i l : SOUND ON: No change. MOVEMENT ON: No change u n t i l T.O. i s within 6 inches of S, who pushes head down beneath i t as i t i s about to h i t i t s head. . Turns head and watches as i t goes past and departs, then turns head towards wall, s i t s l i k e t h i s , s t i l l and quiet u n t i l T.O. approaches again, when S turns and watches i t approaching, passing, and departing, gives a few soft chirps as i t nears him. Pecks at the ground, stands up, head low, pecking at ground, moving around s l i g h t l y i n the immediate area. This type of behaviour continued during the res t of this period. For most of the time, the chick moved slowly around a small area near the middle of the runway, pecking at the ground, and looking downwards. On a few occasions i t gaped, r a i s i n g i t s head as i t did so, and i t would occasionally give a few soft chirps. After about f i v e minutes, i t stretched i t s whole body, f l u t t e r i n g i t s wings, and almost losing balance as it did so. Whenever the T.O. came close (except on two occasions), S turned i t s head and body, and watched i t , then resumed i t s pecking etc. SOUND OFF: No change observed. f 1 2 6 MOVEMENT OFF: Stood s t i l l , head high, looking about, then resumed pecking after about 1 5 seconds. After further 2 5 seconds, begins c a l l i n g loudly, head comes up very high, looking a l l around, approximately 3 feet from the T.O. Chick No. 13: approximate age = 5 1 / 2 hours. I n i t i a l behaviour similar to that of f i r s t chick. In the runway, i t squats on i t s haunches, body just o ff the ground, for about 5 seconds, then stands, head high, c a l l i n g loudly, looking straight forward f o r most of the time. After 3 minutes, c a l l i n g almost ceases, now being le s s loud and much l e s s frequent, s t i l l standing, head medium height. SOUND ON: Remains as above, f o r 1 5 seconds, then begins c a l l i n g loudly and continuously, head held high. MOVEMENT ON: As T.O. approaches ( 6 inches away), S stops c a l l i n g , turns, watches T.O. as i t passes and departs. Then c a l l s again, when T.O. i s 1 foot away, and moves around a small area. As the T.O. approaches again, S jumps back out of i t s path, and immediately jumps forward again, pushing breast at i t , with wings s l i g h t l y r a i s e d . C a l l i n g ceased during t h i s time, resumed again as T.O. departs ( 1 foot away). The t h i r d time around, S pays no attention to the T.O., and t h i s happens f o r the next three times, S moving around, c a l l i n g . On the seventh occasion, S watches i t approach, jumps forward at i t as i t passes, lunges head forward, but does not appear to peck i t . During t h i s time, S i s quiet, c a l l i n g i s resumed when T.O. i s about 2 feet past. The next time, S watches i t approach, c a l l i n g ceases, pecks three times at i t as i t passes, moving forward two paces as i t pecks, and turning with i t , then moves around, looks around, c a l l i n g again when T.O. about 1 8 inches away. S i s running along one wall as T.O. passes the next time, c a l l i n g loudly, and paying no attention to the T.O. 127 On the subsequent occasion, S i s moving around a small area, two-thirds of the way along the runway, with head high, looking around, and c a l l i n g l o u d l y — i t does not appear to respond to the T.O. Thereafter, S continues c a l l i n g loudly, as i t moves around a small area (radius of about one f o o t ) , with head high, and looking around i n several d i r e c t i o n s . Whenever the T.O. i s close, S watches i t b r i e f l y and qui e t l y , then resumes c a l l i n g etc. SOUND OFF: No change observed. MOVEMENT OFF: No change observed—S paid no attention to the swaying T.O. Chick No. 1*+; approximate age = 3 hours. This i s the f i r s t of the second group of subjects, to whom the larger T.O. was presented. S behaved i n i t i a l l y i n a fashion similar to the f i r s t chick's.- In the runway, i t lay on the ground, head at medium height, looking around, began c a l l i n g s o f t l y after 10 seconds, then more loudly. Stood up, stretched whole body, f l u t t e r i n g i t s wings as i t did so, moved few paces forward, head high, c a l l i n g loudly. Head jerking i n several d i r e c t i o n s . Continued i n t h i s manner, occasionally moving forward a few paces, u n t i l : SOUND ON: Quiet as soon as sound s t a r t s . Stands s t i l l , head at medium height, looking straight ahead. Moves head only f o r rest of t h i s period, remains quiet. MOVEMENT ON: As T.O. approaches, S pushes head forward, giving two soft chirps, and turning as T.O. passes. Chirps become much louder and continue as T.O. moves to the end and returns. When T.O. i s within 1 foot again, the c a l l s cease, and S turns hi s head towards T.O., which st r i k e s the side of h i s body. S gives a loud cry, s h i f t s h i s position, shakes himself, turns and watches departing T.O., waddles forward, f l u t t e r i n g wings— appears to have great d i f f i c u l t y i n moving through the shavings on the f l o o r . Stops afte r 6 inches, l i e s down, head up, several loud c a l l s , burst of pecking into shavings. Head comes up, quiet f o r a few seconds, then more loud c a l l s . T.O. i s now 128 approaching once more. S i s quiet as i t comes to within 1 foot of him, flutters/waddles towards i t , swings around aft e r they pass, moves forward after T.O., topples to one side, few soft chirps, head comes up. As T.O. approaches again, S gives a few soft chirps, flutters/waddles to i t as i t approaches, follows i t at a foot's distance f o r about 18 inches. F a l l s to f l o o r , stands up, c a l l i n g loudly; t h i s c a l l i n g continues u n t i l T.O. approaches again, when 3 i s quiet, and watches the T.O. move past him—does not approach i t but l i e s down as i t departs, head sinking down, and eyes clo s i n g . Pecks at the shavings, turns, waddles k inches to the wa l l , l i e s , with head up, facing w a l l — v e r y s t i l l . As the T.O. passes, S gives no response, turns around a few seconds l a t e r , pecks at the ground, gives a few soft chirps, runs to the T.O., about 3 feet away, stops 6 inches behind, and follows i t f o r 2 f e e t . Lies down quie t l y , head low and facing downwards, quiet, with head sinking to the ground, eyes c l o s i n g . Thereafter continues l y i n g l i k e t h i s — h e a d comes up occasionally, and eyes h a l f — o r f u l l y — o p e n , but head quickly sinks down again. Paid l i t t l e further attention to the T.O., would occasionally watch i t b r i e f l y , turning head with i t , but most of the time S did not appear to notice i t . SOUND OFF: No change i n S's behaviour. MOVEMENT OFF: No change observed. Chick No. 15; approximate age = k hours. I n i t i a l behaviour similar to that of the f i r s t chick. Squats on haunches i n runway, body just o f f ground, head at medium height and jerking around, from side to side. Quiet f o r 15 seconds, then soft chirping, quickly becoming louder. Head now higher, looking straight forward f o r most of the time. SOUND ON: S stops c a l l i n g f o r about 20 seconds, pecks twice at the ground, then head comes back up, looks around, c a l l i n g loudly again. MOVEMENT ON: The T.O. h i t s S before he sees i t , he chirps loudly, and r o l l s to one side, regains balance, body f l a t on ground, turns head and watches departing T.O., c a l l s loudly. 129 The next time around, S watches T.O. approach, and pecks at i t twice as i t passes, standing up as he does so. Runs forward up to i t , when i t i s one foot ahead, stands qui e t l y , watching T.O. depart.. On the next occasion, S watches T.O. approach, pecks at i t as i t passes, and moves with i t f o r about s i x inches. Squats on the ground, head up, looking a l l around. As the T.O. passes next time, i t r o l l s over S's body. He chirps loudly, turns head towards i t , pecks at i t , and watches i t depart. On the next s i x occasions, the T.O. passes very close to S's body, without touching i t — h e turns h i s head as i t approaches, pecks once or twice at i t , and watches i t depart. On the next three occasions, S gives a few soft chirps as T.O. approaches, stands up, turns head and body with i t , pecks at i t as i t st r i k e s and moves around h i s body—he does not move out of i t s path. After t h i s S l i e s down, with h i s eyes closed, (the T.O. i s at the other end of the runway). As T.O. approaches, i t touches the top of h i s head; S chirps, r a i s e s head, waddles slowly af t e r i t for short distance (about 6 inches), and watches i t depart, then s e t t l e s back down again, eyes c l o s i n g . The same pattern of behaviour i s seen on the next occasion. A S i s now out of the path of the T.O.; he remains l y i n g down with eyes closed, as the T.O. passes on the next two occasions. Then, h i s head comes up as T.O. approaches, he chirps s o f t l y several times, watches i t pass and depart, then se t t l e s down.again, head slowly sinking towards the f l o o r , and eyes clo s i n g . After t h i s he does not respond to the T.O. f o r the next three occasions, but remains with head and body on the ground, and eyes closed. SOUND OFF: S looks up, eyes open, head moves around to the r i g h t , then forwards, and to the l e f t . Stands up as T.O. approaches, chirps s o f t l y and watches i t pass, turning h i s head and body, and walks slowly forward three paces. Watches i t depart, then looks a l l around. 130 Thereafter, S runs forward a short distance to the approaching T.O., turns as i t passes, and either watches i t depart, or watches and follows i t f o r about one foot. MOVEMENT OFF: S was watching T.O. at the time, having just been following i t f o r one foot. He walked up to i t as i t was swaying, chirped s o f t l y several times, moved around i t , and stood, with h i s back to i t , head medium high, looking towards a corner (nearby) of the runway. Chick No.'16; approximate age = 5 hours. I n i t i a l behaviour similar to that of the f i r s t chick. Stands i n runway, looking a l l around. Loud c a l l i n g after h a l f a minute, head held high. Moves feet s l i g h t l y , turning slowly around. SOUND ON: Stands s t i l l and quiet f o r 15 seconds, then resumes loud c a l l i n g , head held high. MOVEMENT ON:' The T.O. h i t s him before he sees i t , he chirps qu i e t l y , turns, and walks quickly after i t , q u i e t l y , f o r 3 feet. Stops, watches i t pass around pulley wheel, runs to i t as i t approaches again, turns with i t , follows s t e a d i l y f o r k feet. Stands s t i l l and quiet, head moving around near ground. The T.O. h i t s him again as i t passes, he chirps, moves quickly out of i t s path, watches.it depart, then looks i n several d i r e c t i o n s . Runs to T.O. as i t approaches again (3 feet away), turns with i t , chirping s o f t l y , moves quickly a f t e r i t for one foot, as i t departs. Thereafter i t pecks at the ground, chirps,, preens (once or twice), and moves around i n small area, when the T.O. i s distant. When i t approaches, S moves towards i t , turns, watches, and (usually) follows f o r 6 inches to one foot. S chirps s o f t l y both when the T.O. i s near and when i t i s more d i s t a n t — i t s chirps are louder and more frequent when the T.O. i s within one foot (either way) of i t . SOUND OFF: S was pecking at the ground at the time, i t looked up, stood s t i l l and quiet f o r 15 seconds, u n t i l T.O. passed i t , when 131 S pecked at i t , watched i t , and f l u t t e r e d quickly a f t e r i t f o r one foot. Stood pecking at the ground, and moving head around just off the ground. Behaviour towards approaching -T.O. continued as above. MOVEMENT OFF: S continued looking around the ground, pecking, and s o f t l y and inte r m i t t e n t l y chirping. I t was 3 feet from the swaying T.O. Chick No. 17: approximate age = 3 1/2 hours. I n i t i a l behaviour similar to that of the f i r s t chick. In runway, body f l a t on ground, head f a i r l y high, head moving around, quiet for 30 seconds, then soft c a l l s quickly becoming louder. Stands up, moves forward a few paces, head up high, c a l l i n g loudly, moving s l i g h t l y forward most of the time. Continues u n t i l : SOUND ON: . Stops c a l l i n g , stands s t i l l , head thrust forward, quiet. After 15 seconds lowers s e l f to ground, looks around near ground, pecks several times, remains quite s t i l l f o r 30 seconds, then preens at bottom of breast. MOVEMENT ON: Remains quiet as T.O. approaches, turns head and -watches when T.O. 3 feet away. Does not watch T.O. depart, some loud c a l l i n g (T.O. just past pulley wheel at f a r end), head up high, looking i n several d i r e c t i o n s . As T.O. approaches (2 1/2 f e e t ) , S turns, watches, waddles forward a few paces, and moves behind T.O. f o r about 6 inches, chirps s o f t l y four times. Set t l e s back on ground, body f l a t , head sinks slowly down, jerks up, goes slowly down again, eyes c l o s i n g — h e a d jerks up again, looks around, pecks at ground, long burst of soft chirps. Looks up as T.O. approaches, chirps continue, watches T.O. u n t i l i t passes him, then looks back down towards ground, head sinks down, eyes c l o s i n g j head comes up again, eyes open, waddles forward and to the r i g h t , s e t t l e s down near wall, facing middle of runway, almost. Thereafter S would respond to approaching T.O. about ^ every second time i t passed, by looking up, standing almost upright, walking j e r k i l y towards the middle of the runway, and after the departing T.O., about one foot, chirping s o f t l y and inte r m i t t e n t l y . I t would then l i e down again near the path of 132 the T.O., head going down to ground f a i r l y quickly, and eyes clos i n g . Head would either rest on the ground, or just above i t . On about h a l f the occasions when T.O. passed, S would make no response. Towards the end of th i s period, S responded even l e s s than t h i s , and appeared to be "asleep" f o r much of the time. SOUND OFF: No change from the last-mentioned behaviour. MOVEMENT OFF:' No change—the T.O. was about f i v e feet from S, at the f a r end of the runway, and S had his back towards i t . Ghick No. 18; approximate age = 2 1/2 hours. I n i t i a l behaviour similar to the f i r s t chick's. In runway, S lay on ground, head at medium height, looking around. Quiet f o r 20 seconds, then soft c a l l s , which became s l i g h t l y louder, but were not as loud as those of most other chicks. Frequent pauses, when chick was quiet. Did not stand up, or s h i f t p o s i t i o n u n t i l : SOUND ON: This occurred i n the middle of a quiet period. S remained quiet, looking about him, head up high, stood up af t e r 15 seconds, stretched whole body, f l u t t e r i n g wings, walked j e r k i l y forward about 6 paces, head down towards ground. Stood with head moving near ground for rest of t h i s period, quiet, s h i f t i n g feet s l i g h t l y . MOVEMENT ON: The T.O. r o l l e d over h i s back before he saw i t , S chirped loudly, r o l l s body sideways, stands up, looking around, and then looks towards ground, few soft chirps. As T.O. approaches again, S s t i l l chirping s o f t l y , head comes up, watches T.O. as i t passes near him, runs, with some d i f f i c u l t y a f t e r i t , f or about one foot, pecks at i t , then stands watching i t f o r about 3 feet more. Settles down on ground, head goes down to ground, pecks slowly several times, quiet. Thereafter S would look up as T.O. came within 1 foot of him, turn h i s body around with T.O. as i t passed, and (usually) 133 waddle no more than one foot after i t . Occasional soft chirping, but mostly quiet. After 5 minutes of t h i s , S did not respond as T.O. passed him four times. When T.O. was not close to him, S would have h i s head down on the f l o o r , f o r most of the time, eyes closed, or would have head just off the f l o o r , pecking—often pecked just a f t e r T.O. had passed. S was nearer one of T.O.'s paths, than the other, and he would respond when T.O. passed along th i s side more often than he would when i t passed on other side. His waddling was almost a series of short jumps—appeared to have d i f f i c u l t y with the small p i l e s of wood shavings. SOUND OFF: No change i n S's behaviour, responded, as above, twice. MOVEMENT OFF: S watched the swaying T.O., l y i n g on the ground, head well forward of h i s body, f o r 15-20 seconds, then stood up, gave few soft chirps, and clumsily ran over to T.O., pecked at i t twice, then s e t t l e d on the ground, head at medium height, intermittent soft chirps. Chick No. 19: approximate age = k hours. I n i t i a l behaviour similar to that of the f i r s t chick. In runway, S stands almost upright, legs s l i g h t l y bent, looks a l l around, then down at the ground. Begins c a l l i n g loudly after k5 seconds. Moves around small area, s t i l l c a l l i n g loudly. SOUND ON: No change i n S's behaviour. MOVEMENT ON: Turns head towards T.O. as i t comes within 2 feet of S, turns body as i t passes, quiet now, follows f o r 6 inches watches i t depart f o r k f e e t , then looks a l l around, quiet. As i t approaches next time, S walks towards i t , when i t i s s t i l l 2 1/2 feet away, pecks at i t several times, follows fo r about 6 inches, then watches f o r 2 f e e t , and then looks across to w all, then down at the ground. Few soft chirps, moves forwards s l i g h t l y . Squats on ground facing away from T.O. as i t approaches again, head low, and moving around just above ground. Pecks at ground several times. Stands up, moves towards wall, no response to T.O. as i t passed again. Did not respond on next f i v e occasions, but moved around near wa l l , facing wall mostly, some pecking at ground. Then turned and ran towards T.O. When i t was 3 1/2 feet away, pecked at i t twice, turned aft e r i t had passed, and walked 6 inches towards i t , then looked around, occasionally pecking and s o f t l y chirping. Thereafter S approached the T.O., and turned with i t , but did not follow, nor did he watch i t for more than 2-3 seconds as i t departed. During the res t of the time, S moved slowly around near the middle of the runway, head moving a l l around,, mostly near the ground, occasional peck at ground, quiet. SOUND OFF: S looked up at the T.O. as i t passed, few f a i r l y loud chirps, then ran aft e r i t and stayed with i t f o r just under k feet. Stood watching i t as i t passed around pulley wheel, then ran to i t , and followed i t f o r one foot, then turned towards wa l l , pecking few soft chirps, head moving around near ground. As T.O. approached on next two occasions, S looked up, ran i n towards i t , followed for about 6 inches, watched i t depart f o r one foot more, then stood looking about. MOVEMENT OFF: S continued moving head around near ground, quiet f o r 20 seconds, then head came up high, loud c a l l s , moved quickly around and towards side of runway. T.O. was approximately 3 feet from him. Chick No. 20: approximate age = 3 1/2 hours. I n i t i a l behaviour similar to that of f i r s t chick; as E was carrying him towards runway, S pushed backwards out of E's hands, and f e l l to the f l o o r . Immediately stood up, c a l l i n g very loudly. As E put h i s hands towards him, S ran behind one leg of the table on which the runway stood, and i t was with some d i f f i c u l t y that E picked him up again. S c a l l e d loudly a l l t h i s time, u n t i l back i n E f s hands. When placed i n runway, S ran about i n middle of i t , c a l l i n g loudly, wings out s l i g h t l y from body, head high. This continued, with short breaks i n both v o c a l i z a t i o n and running (these did not always coincide), u n t i l : 1 3 5 SOUND ON: Chick stopped running, stopped c a l l i n g , stood with head high, and straight i n front of body, f o r h a l f a minute, then began c a l l i n g again, somewhat les s loudly. Stayed i n same posit i o n , head moving around, c a l l i n g (with short breaks) u n t i l : MOVEMENT ON: As T.O. approaches S, he stops c a l l i n g , pecks at i t as i t passes, turning body with i t , few soft chirps as he follows i t slowly f o r 6 inches, then stands, looking upwards, c a l l i n g loudly, u n t i l i t approaches again, when S turns towards' i t , walks towards i t ( 3 feet away), pecks at i t twice, turning with i t , follows for 6 inches. Watches i t move to end of runway, then squats on haunches, body just off the ground, head moving around near the ground, with an occasional peck at the ground. S does not respond to the approaching T.O. on the next four occasions, then stands upright, runs towards i t as i t approaches ( 3 1 / 2 f e e t ) , pecks at i t three times, turns, walks a f t e r i t f o r one foot, stands pecking at ground, moving to l e f t ' s l i g h t l y . For the next s i x times, S watches T.O. as i t approaches, runs towards i t f o r about one foot, turns with i t , does not follow, but moves slowly about a small area, head turning a l l about, some pecking, quiet. Then S runs to i t ( 1 foot away), turns, pecks i t once, follows for over k feet, watches i t pass around pulley wheel, runs to i t again, turns, and follows f o r one foot. Thereafter, moves around, head low, some pecking at ground, occasional soft chirping. When the T.O. approaches, S watches i t , then runs towards i t , turns, but does not follow. SOUND OFF: Behaviour as above for one minute, then S l i e s down near middle of runway, facing w a l l , head sinks downwards, pecks l i g h t l y at ground once, head goes onto ground, eyes close. Does not respond to T.O. MOVEMENT OFF: S remains l y i n g on the f l o o r i n t h i s fashion. Head comes up f a i r l y quickly once, eyes open, but goes back down again, eyes closed, within 5 seconds. Chick No. 2 1 : approximate age = 3 1 / 2 hours. I n i t i a l behaviour similar to that of the f i r s t chick. In runway, S l i e s on ground, head at medium height, beak horiz o n t a l . 136 Head f a i r l y s t i l l , quiet f o r 20 seconds, then soft chirping, head moving about more, chirping becomes much louder within a few seconds. S raises s e l f up on haunches, legs well bent under body. Remains thus f o r re s t of t h i s period. SOUND ON: Chick stops c a l l i n g within 2-3 seconds, holds head s t i l l , looking straight forward. After 10 seconds gives a few soft chirps, stands up, walks slowly forward about s i x paces, looks towards one wall, moves towards i t , few louder c a l l s , pecks at ground near wall. Stays moving slowly around, and looking a l l around, i n t h i s area. MOVEMENT ON: No change i n S's behaviour, does not appear to notice T.O. f o r the f i r s t 8 times i t passes him, facing wall most of the time. Moves to middle of runway (T.O. at one end), s e t t l e s down, body f l a t , head low, head moving near the ground. T.O. comes up from behind S, and r o l l s over h i s body. S gives loud chirp, and shuffles quickly to l e f t , looks up at i t ' very b r i e f l y , then s e t t l e s down again, head low, eyes h a l f closed. On the next four occasions, S looked up as i t approached (1 f o o t ) , and shuffled awkwardly towards i t as i t passed. Watched i t as i t went f o r no more than one foot, then head sank down again, eyes clo s i n g . On the next occasion, S shuffled i n towards i t as i t came close, chirped s o f t l y 3 times, pecked at i t twice, turned body as i t passed, shuffled a f t e r i t f o r about 6 inches, then se t t l e d down again, head moving low near the f l o o r . Following t h i s , S, (who had s e t t l e d i n one path of the T.O.) was struck by i t as i t passed. He made no noise, raised h i s head and watched i t b r i e f l y , then head went down onto ground, eyes clo s i n g . The same thing happened on the next occasion, except that S chirped s o f t l y twice, and pecked twice at the T.O. as i t went by h i s head. S then shuffled s l i g h t l y to one side and forwards a few inches. Before T.O. returned, S stood up, head moving a l l around, stretched l e f t foot behind him, c a l l e d f a i r l y loudly about 18 times, while moving across and i n the area of one wall. Settles down there, does not respond to the T.O. as i t approaches, during the r est of t h i s period, head sinks to ground, eyes close. 1 3 7 SOUND OFF: No change i n chick's behaviour. Looks up b r i e f l y once, head goes down again within 5 seconds; T.O. was at f a r end of runway, behind him, at thi s time. MOVEMENT OFF: S remained l y i n g i n same place. Chick No. 22: approximate age = 3 hours. I n i t i a l behaviour similar to that of the f i r s t chick. In runway, stood, looking around, moved forward one foot, then to r i g h t , few soft chirps, stood s t i l l f o r about h a l f a minute, then walked back to where he had been placed, turned slowly around, few soft chirps. Head goes down towards ground, looks around near ground. Remains thus, with s l i g h t movement, and an occasional burst of soft chirping, u n t i l : SOUND ON:. Looks up, head quite s t i l l , stays l i k e t h i s f o r about 20 seconds, then head goes down near ground again, moves slowly around, as before, quiet the whole time. MOVEMENT ON: As T.O. approached f o r the f i r s t time, S turned towards i t , and waddles (on haunches) towards i t , remained quiet, turned as i t passed, and watched i t depart. Sank onto ' haunches again, waddles forwards a few inches, looking towards ground, head stretched down i n front of him. The chick behaved i n a similar fashion on the next two occasions, then, as T.O. was passing again, he pecked at i t once, turned and watched i t depart. S then s e t t l e d down, body f l a t , on ground, head just off the ground, and s t i l l , eyes h a l f closed. He did not react to the approaching T.O. The next time around, S looked up as T.O. was approaching, shuffled towards i t , using h i s wings, pecked at i t , turned with i t , and watched i t go. This happened again on the next occasion, but the chick also followed i t slowly f o r about one foot, s h u f f l i n g forward, on haunches, i n a very clumsy manner. He then s e t t l e d down again, head on ground, eyes closed. 1 3 8 As the T.O. approached, he looked up, watched i t pass, shuffled forwards 6 inches, chirping s o f t l y . This continued on the next f i v e occasions, then the chick, who had set t l e d down again, did not respond to the approaching T.O. Thereafter, i t looked up at the T.O. ( 1 foot away) turned i t s head and body, as T.O. passed, and watched i t depart. It did not follow, u n t i l the l a s t time, i n th i s period that T.O. approached, when i t looked up as T.O. approached, turned / as i t passed, and walked quickly behind i t f o r about 2 f e e t . SOUND OFF: S stopped following, looked straight ahead, standing s t i l l , few soft chirps, watched T.O. as i t rounded the pulley, ran over to i t , peeked at i t once, turned towards wall, looked a l l around, few f a i r l y loud chirps, pecked at the ground twice, s e t t l e d down, body f l a t on ground, head up and looking around. As T.O. approached again, i t looked towards i t , but did not get up. Quiet. Looked towards i t , without getting up, the next two times i t d i d not turn towards T.O., but held i t s head low near the ground, looking around. MOVEMENT OFF: S's head slowly sank onto the ground, eyes closed. After 1 0 seconds i t jerked i t s head up, stood up, walked forwards 6 paces, s e t t l e d down again, no c a l l i n g . Chick No. 23: approximate age = 6 hours. I n i t i a l behaviour similar to that of f i r s t chick. When placed i n runway, S stood, qui e t l y , with head high, looking a l l around. It moved quickly forward, after 1 0 seconds, c a l l i n g loudly. Ran i n several d i r e c t i o n s , a f t e r t h i s , head moving a l l around, and c a l l i n g loudly almost continually. Short bursts of running, covering between one and two feet each time, with pauses of about f i v e seconds between them. SOUND ON: Chick looked up, head s t i l l , quiet, f o r 1 0 seconds, then continued as before. MOVEMENT ON: The f i r s t time T.O. approached S, he looked towards i t , turned head and body as i t passed, quiet during t h i s time, then resumed previous behaviour. 1 3 9 On the second occasion, S turned head and body towards T.O., quiet as soon as he attended to i t , then few soft' chirps as i t passed. Remained quiet (few soft c h i r p s ) . Looked a l l around, head at medium height, moving about a l i t t l e . On t h i r d occasion, S turned as before, but also followed c l o s e l y f o r 3 f e e t , around the pulley wheel, then pauses, watches, then runs up to i t ( 1 / 2 way along runway), follows f o r another 2 f e e t , quiet, then watches i t depart. Few soft chirps, then quiet, then chirps again as T.O. comes back, turns as i t passes him, follows f o r 2 f e e t , pecking at i t , running up to and i n front of i t . This continues, almost continuously, f o r 2 1 / 2 c i r c u i t s , usually l e t t i n g T.O. get about 3 f e e t i n front of him, then running up to i t and pecking at i t , but also these are occasions when he follows about k inches behind T.O., keeping steadily up with i t , sometimes pecking at the ground as he follows l i k e t h i s . Stops at one end, watches T.O. depart, runs to i t about 1 / 2 way down the pen, as i t approaches, follows i t around pulley at same end. C a l l s loudly when i t moves 5 feet ahead of him, quiet when i t returns (about k feet away). Follows, sprinting up to i t , then stopping while i t progresses about 3 f e e t ; t h i s goes on for one complete c i r c u i t . A sudden loud noise outside—heavy footsteps after door closes l o u d l y — S stops, stands s t i l l , head up, looking a l l around, head cocked on one side, quiet. Continues bursts of following, with pauses i n which i t watches T.O. f o r one to two fee t , as i t runs up to T.O., i t usually pecks at i t at l e a s t once. This, again, i s interspersed with regular, steady following, about inches behind T.O. Such behaviour continues u n t i l the end of t h i s period. This chick was the strongest follower of them a l l . SOUND OFF: No change. Occasional peck at the ground i n pauses between bursts of following. MOVEMENT OFF: S was about 6 inches behind T.O. at the time, and following i t . S moved quickly up to i t , pecked at i t twice, then moved slowly around i t one and a h a l f times, looking straight ahead mostly. Then stood, head down towards the ground, r i g h t side towards swaying T.O. I*f0 Chick No. 2*+; approximate age = k hours. I n i t i a l behaviour similar to that of the f i r s t chick. Inside runway, squats on haunches, body just clear of the ground, looks a l l around, head medium height. Quiet f o r 1 5 seconds, then soft chirps, quickly becoming louder. Stands up after 1 1 / 2 minutes, c a l l i n g loudly, head high, moves around a l i t t l e , i n same area. This continues u n t i l : SOUND ON: Chick immediately quiet, stands s t i l l , with head forward, medium height. Walks forward few paces, head goes down near the ground, moves around i n th i s fashion, quiet. MOVEMENT ON: S turns towards T.O. as i t approaches, chirps loudly as i t brushes against h i s body, watches i t depart, then stands looking a l l about, quiet. As T.O. rounds pulley wheel, S gives a few moderately loud c a l l s , and squats on hi s haunches, head straight i n front of body. As i t approaches again, S looks up, turns as i t passes, and watches i t depart. Chirps several times f a i r l y loudly, waddles/shuffles a f t e r i t about 6 inches, pauses, watching i t , then runs quickly up to i t , f l u t t e r i n g wings. Watches i t as i t rounds end of runway, then runs across to i t , pecks twice, then s e t t l e s on the ground, back towards pulley-system, head f a i r l y high. As T.O. approaches around pulley, S turns h i s head to i t , jumps up, chirping s o f t l y , turns, watches i t pass him and depart, runs to i t when i t i s 3 feet away, stops, watches i t . When i t rounds pulley at other end, S runs to i t , follows f o r 1 foot, pecking at i t several times, watches i t depart, pecks once at the ground, s e t t l e s down on ground, head high, then head sinks downwards, eyes c l o s i n g . On the next four occasions, S gave no response to T.O. After t h i s , S runs forward to i t , approaching at a distance of 3 feet. Chirps many times s o f t l y , does not turn with i t , but faces opposite d i r e c t i o n , stands, looking a l l about, se t t l e s down1on ground, head just off the ground, eyes h a l f closed. As i t passes again, S looks up at i t , chirps s o f t l y , watches i t pass (turning head) and watches i t depart. Ikl Thereafter, S looks up at i t and walks about 6 inches towards i t , as i t approaches. Usually pecks once at i t , turns, but does not follow. Occasionally S would not approach i t , but merely watch i t . SOUND OFF: S continues to look up at approaching T.O., move to i t about 6 inches, turn, and watch i t depart. In between these times, S would remain with body on the ground, head low, looking a l l around on the ground, with an occasional peck at the ground. MOVEMENT OFF: S's head i s down on the ground just as the movement i s turned o f f , h i s eyes are closed, and he remains l i k e t h i s u n t i l removed from the runway. Chick No. 25: approximate age = V hours. I n i t i a l behaviour similar to that of the f i r s t chick. In runway, S l i e s on ground, head up and looking about, f o r about 10 seconds. Few soft chirps then followed by ha l f a minute of quietness. S looks down towards the ground, head moving to l e f t , forwards, and to the r i g h t . Several more soft chirps. Head comes up, looks a l l around. Head goes down again, looking around the ground. Continues i n t h i s fashion, with occasional soft chirps, u n t i l : SOUND ON: S looks up, head quite s t i l l , stands up, quiet, moves forward about 2 fee t , walking slowly, head jerking from side to side. Squats on haunches, head medium height, head goes lower, moves around near ground. Few soft chirps. Gapes three times, stands up, head high, body sinks back onto ground, head low. MOVEMENT ON: The T.O. r o l l s over S's body before he sees them, he turns, watches i t , gives few soft chirps. As the T.O. returns, S watches i t , turns h i s head and body, watches i t depart, few soft chirps. The next time he waddles towards i t (1 f o o t ) , pecks at i t twice as i t passes, (at the top of the lowest b a l l ) , shuffles forward afte r i t f o r 6 inches. Observer gets strong impression that S can hardly use his legs. Ik2 As i t approaches again, S shuffles towards i t , pecks at i t , chirps moderately loudly and frequently. After t h i s , S s e t t l e s down, head down just off the ground occasionally pecking, but eyes h a l f closed f o r most of the time. On next two occasions he does not react to the approach of the T.O. Thereafter he watches i t approach, chirping a l o t , waddles towards i t , pecks at i t (usually) and at the ground when i t has passed, and would sometimes follow i t f o r 6 inches to one foot as well. He inv a r i a b l y approached i t whenever i t was about 2 feet near him. SOUND OFF: S looks up and around to the r i g h t , then forwards again and to the l e f t . Makes no noise, then head goes down to ground, eyes h a l f closed, beak on the ground. MOVEMENT OFF: S remains on the ground, both body and beak r e s t i n g on i t , eyes h a l f closed. Chick No. 2 6 ; approximate age = 3 hours. I n i t i a l behaviour similar to that of f i r s t chick. In the runway, S stood with legs bent underneath him, body high off the ground, rocking forwards and backwards, head at medium height, looking a l l around. S h i f t e d l e f t leg forward, and gave a few soft chirps after 5 seconds, quickly became louder. Moved forward 6 inches aft e r one minute, then to the wall on i t s l e f t , after 2 0 seconds more. C a l l i n g loudly almost the whole time. This type of behaviour continued throughout t h i s period. SOUND ON: Stood s t i l l , head stretched forward, quiet, f o r about 1 0 seconds, then gave a few soft chirps, and walked forward *+ paces. Head went down to near ground, pecked at or near r i g h t foot, walked forwards again, few soft chirps, then an unusual extended cry, of moderate i n t e n s i t y , and of peculiar composition, made as head came forward and upwards. Stood s t i l l a f t e r this,, looking around, head at medium height, and quiet. MOVEMENT ON: The T.O. brushed against i t s body, before S saw i t , S ran/shuffled sideways, l o s i n g balance and f a l l i n g to the ground 1^ 3 on i t s r i g h t side. Immediately stood up again, using i t s wings. Several loud c a l l s at t h i s time. Stood, head high, looking a l l around, c a l l i n g loudly. Moves over to wall, and walks around a small area there. Does not appear to notice T.O. as i t passes on'next three occasions, then squats down on i t s haunches, quiet,;as T.O. approaches. S watches i t pass him, then stands up, few soft chirps, watches i t depart. Squats down on haunches again, looking around, quiet. As T.O. approaches again, S stands up; as i t passes, he moves up to i t , follows i t f o r one foot, watches i t depart further, s e t t l e s down on ground, body f l a t , head low, pecks several times at ground, quiet. Stands up as T.O. approaches again, walks to i t as i t passes, several soft chirps, peeks at i t twice, follows i t f o r six inches, stands watching i t , turns away, s i t s down, body f l a t , head up and forward. As T.O. approaches again, S turns head and watches i t . I t passes against h i s body, he stands up, loses h i s balance, quickly regains i t , quiet, turns and watches i t depart. The next time, S stands up when T.O. i s 2 feet away, turns, chirping, as i t passes, walks one foot after i t and watches i t . Moves around i n the i n t e r v a l , several soft chirps, l i e s down on ground, head low, pecks several times at ground. As i t passes the next time, S watches i t , turning head only. Looks back down to ground, as before. On the next occasion, S walks j e r k i l y forward as i t approaches (1 f o o t ) , turns head only as i t passes, looks a l l around, s t i l l quiet. The next time, he turns his head, watches i t approach, pass, and depart. The same thing happens on the next occasion. Then, S walks clumsily forward, stepping on one foot as he moves the other, watches i t pass and depart, turning head and body. Se t t l e s down on ground, head low and moving just above ground. Stands up as T.O. approaches, walks towards i t ( 6 inches) turns, watches i t pass, follows for about 6 inches, few soft chirps. S e t t l e s down again. The next time, S stands up, walks towards i t as i t passes, and thrusts beak forward, rubbing i t against the side of the lowest b a l l . S e t t l e s down again as i t departs, head low, almost touching the ground, remains s t i l l . Thereafter S does not get up again, but always looks up as T.O. approaches (about 2 feet away), turns head, and usually body, as i t passes, watches i t depart for about one foot, remains quiet. SOUND OFF: No change i n S's behaviour. MOVEMENT OFF: Head sinks onto ground, eyes h a l f closed. Remains thus f o r about h a l f minute, then jerks head up, eyes open. Head quickly goes back down again (within 5 seconds), does not look at T.O., eyes close, quiet. (2) SECOND EXPOSURES Approximately 2k hours after the f i r s t exposures, the chicks were again placed, i n d i v i d u a l l y , i n the runway. The target-object was the same (within each of the two groups) as the one used on the i n i t i a l exposure. No sound was used; the T.O. was moving continually from before the chick was placed i n the runway u n t i l after i t was removed. Each exposure lasted f o r 1 5 minutes, and recordings were made i n the same manner as previously. The chick was placed i n the centre of the runway, facing the T.O., which was rounding a pulley wheel at the time. Results A l l of the chicks gave loud c a l l s as they were released from E's hand i n the runway. These ceased as the T.O. approached for the f i r s t time, except i n the case of chicks 1 , 1 5 , and 1 8 , who were moving near the walls of the runway, and d i d not appear to see the T.O. u n t i l i t had moved around two or three c i r c u i t s . Thereafter t h e i r behaviour was similar to that of the re s t of the chicks. As the T.O. approached, the chicks would turn either t h e i r head or head and body towards i t . They would usually walk or run towards i t . Then they would turn with i t as i t passed, and follow f o r about 1 8 inches, on the average, for the f i r s t s i x or eight t r i a l s . They then watched the departing T.O. fo r up to 2 feet. Some would run up to i t again aft e r a short pause, move with i t f o r le s s than one foot, and watch i t again. The i n t e n s i t y of these responses to the T.O. c l e a r l y diminished towards the end of the exposure. Most of the chicks peeked at the T.O. on a number of such occasions, and also pecked at the ground while, or just a f t e r , following i t . i»+5 From the time when the loud c a l l i n g ceased (usually when the T.O. approached for the f i r s t time; see above), no further loud c a l l s were heard, but, i n many cases, the chicks would chirp s o f t l y after pecking at the T.O., and/or while pecking at the ground as the T.O. departed. Such soft chirps were also frequently heard when the chicks were moving around, head usually near the ground, i n the i n t e r v a l s between the approach of the T.O. During these i n t e r v a l s the chicks would move around i n an area of about 1 8 inches to two feet square, with head down near the ground. They would often peck at the ground, and would also r a i s e their heads to medium height (beak horizontal) and look around them. Five of them lay on the ground, with head up, or with head down near the ground, during several of the i n t e r v a l s . One chick (No. 1 5 ) rested h i s beak on the ground, and closed h i s eyes, during two consecutive i n t e r v a l s , showing the t y p i c a l response, however, (see above) as the T.O. approached. At a sudden sharp noise (e.g., a door slamming somewhere i n the b u i l d i n g ) , the chicks would cease th e i r current a c t i v i t y , r a i s e t h e i r heads, usually cocking them s l i g h t l y to one side, keep t h e i r heads forwards, or (less commonly) move them j e r k i l y around. After 2 or 3 seconds, the chicks would resume the i r previous a c t i v i t y , or walk forward several paces, and then resume i t . Chick No. 2 1 stood preening behind i t s l e f t wing f o r about 1 0 seconds, and then again 2 0 seconds l a t e r , during one i n t e r v a l between the approaches of the T.O. During the 2 0 seconds, the T.O. passed, and the chick showed a t y p i c a l response towards i t . None of the chicks followed the T.O. f o r more than h a l f the length of the runway, on any given occasion, including those which ran a f t e r i t several times on the same occasion. li+6 CHAPTER IV DISCUSSION OF THE OBSERVED BEHAVIOUR, WITH REFERENCE TO THEORIES OF IMPRINTING It should be stressed, at the s t a r t , that the "non-imprinting conditions" are not necessarily THE normal conditions i n which domestic fowl f i n d themselves, nor are the conditions for the imprinting group necessarily t y p i c a l i n a l l respects of those i n which other investigations have been performed. Thus, any statements made, with respect to the behaviour of either group, w i l l apply only to the s p e c i f i c chickens observed— whatever application these statements may have to chickens i n general can only be known after further i n v e s t i g a t i o n has been made, taking into account any procedural differences between t h i s and other studies. While i t i s f e l t that the behaviour described i n the previous chapter i s f a i r l y t y p i c a l of chicks i n general, both i n d i v i d u a l and group differences were found, and these were correlated with differences i n the stimulus s i t u a t i o n i n many cases (e.g., with the number of other chicks present, and with the presence of a hen, e t c . ) . Stressing t h i s point guards against describing any given item of behaviour as i n s t i n c t i v e . o r learnt, or by means of any other such "umbrella" terms. One further i n i t i a l point to be considered i s that the "non-imprinting" groups were not non-imprinting at a l l , i n pr i n c i p l e at l e a s t — w i t h the exception of the single chick i n 1**7 group 1/0. These categories are used at a descriptive l e v e l , s o l e l y to bring out the f a c t that the one group was not exposed to the more a r t i f i c i a l experimental conditions, while the other group was. The most obvious c h a r a c t e r i s t i c of the non-imprinting chicks was the alternation between periods of rest and periods of a c t i v i t y . With age, a c t i v i t y increased at the expense of r e s t . Secondly, as mentioned e a r l i e r , the movements of older chicks were better controlled than those of younger b i r d s — i n preening or walking, f o r example, the older ones l o s t balance les s often than the younger ones. In l i n e with the increased a c t i v i t y of older chicks, the distance they covered during locomotion became greater. Older chicks also pecked more often and did more preening than younger ones. One r e s u l t of increased a c t i v i t y — o f locomotion i n p a r t i c u l a r — i s to bring the animal into contact with a wider v a r i e t y of s t i m u l i . A pattern of behaviour which did not change i n either form or latency, as f a r as could be judged, was the s t a r t l e response. The f a c t that a noise, which would e l i c i t t h i s response during the chick's active periods, did not always do so during i t s r e s t periods, together with the f a c t that older chicks were active f o r longer than younger ones, i s probably s u f f i c i e n t to account f o r the increased incidence of t h i s response i n the older c h i c k s — i n other words, i f the s t a r t l e pattern i s taken as an indicator of anxiety, then, based on t h i s behaviour alone, there i s no evidence which suggests I*t8 that anxiety increases with age. This response, however, i s not f e l t to be i n d i c a t i v e of anxiety, but rather to precede any such state or response of that nature. I t s function appears to be to a l e r t the animal to a sudden change i n the environment. This does not necessarily imply that i t i s a response to sudden danger, even though the animal may subsequently f l e e from the source of the sudden change i n the environment ( i . e . , after having perceived or i d e n t i f i e d the new stimulus s i t u a t i o n as being dangerous, or, at l e a s t , as one which has not been experienced before). An analogy may be drawn with the sounding of an a i r - r a i d siren during wartime—although, i n adults and older children, anxiety responses may be, and are intended to be, conditioned to the sudden intense change i n auditory stimulation, young children, at f i r s t at l e a s t , are not "alerted to the danger" by the sir e n , but are simply "alerted". For a l l they know, i t might be a sign that the toyshops or candy stores are opening. The young chick must surely be thought of as corresponding to the young c h i l d , rather than to the adult. In support of t h i s i s the f a c t that the chick's behaviour reverted to i t s prior form within a few seconds a f t e r the disturbance; i t did not give the loud c a l l s usually r e f e r r e d to as d i s t r e s s c a l l s , nor d i d i t f l e e to the walls of, or around, the pen. In contrast to t h i s , the broody hens showed the same s t a r t l e response, but continued i n that fashion f o r long after the chick had ceased to do so. I t i s thought that the hen, as a r e s u l t of i t s experience on numerous 1^ 9 occasions i n the past on which a sudden disturbance had l e d to the entrance of one of the s t a f f of the farm into i t s l i v i n g quarters, and to some form of r e l a t i v e l y d i s t r e s s i n g treatment, would have had, 'like the adults when the sire n sounded, anxiety responses conditioned to any sudden change i n auditory stimulation. The young chick had experienced only two or three such events,, therefore was alerted to the change, i n a neutral sense, rather than being alerted i n the sense of being emotionally aroused. The response appears to be r e f l e x i v e i n nature, involving several components, rather l i k e the Babinski response i n infa n t s , but somewhat more complex. Another behavioural item which i s generally taken to be in d i c a t i v e of anxiety i s defecation. This was infrequent on the f i r s t day, somewhat more frequent on the second. Does t h i s imply that anxiety increases i n similar fashion? Since defecation i s a posi t i v e function of amount of food ingested, and since i t was noted that pecking increased with age, a much more d i r e c t explanation suggests i t s e l f . With regard to anxiety responses on the occasions when the chick was v i o l e n t l y disturbed, namely, when i t was taken from the incubator, and when the water was changed (vi a the hose) at the end of the f i r s t day, there was no evidence whatsoever which suggested either that a chick, one or two hours of age, was not extremely disturbed by the former event, or that i t was more strongly disturbed l a t e r than e a r l i e r . The chicks, removed from 1 5 0 the incubator at a younger age than c e r t a i n s l i g h t l y older ones, struggled and c a l l e d loudly when E picked them up to at l e a s t the same degree as did the s l i g h t l y older ones. A l l chicks were removed and taken to the observation pen (being weighed enaroute) at an age e a r l i e r than that at which Hess ( 1 9 5 9 ) , f o r example, suggests that they show fear responses. C l e a r l y , some of what i s referred to above as struggling consists of presumably r e f l e x responses to changes i n equilibrium, which, per se T do not necessarily imply any emotional state such as fear or anxiety, but, even i f t h i s were the complete explanation f o r such movements, the other forms of behaviour shown simultaneously (e.g., the c a l l i n g , pecking(?), and running around the small cage i f E did not pick up the chick s u c c e s s f u l l y ) , would s t i l l suggest an explanation i n terms of anxiety. With chicks hatched within a few hours, and l e f t undisturbed i n a constant environment f o r these few hours, one could equally well argue that the e f f e c t of the sudden disturbance would be greater, the more recently the chick had hatched. With regard to the changing of the water i n the pen at the end of the f i r s t day, a l l chicks were disturbed by t h i s event, as seen by their behaviour. Since, however, by t h i s time the chicks were at the age at which anxiety or fear responses have previously been observed, t h i s provides no further evidence f o r or against the present position that anxiety can be aroused, and manifest i n the chick's behaviour, from the time of hatching 1 5 1 rather than from nine to ten hours thereafter (Hess, 1 9 5 9 ; Moltz, I 9 6 0 ) . I t i s granted that, for much of the f i r s t day, the newly-hatched chick spends a good deal of time r e s t i n g , and that, during t h i s time, i t does not show the s t a r t l e response as re a d i l y as when i t i s more active during that day. I t i s also granted that the chick may not f l e e so much at t h i s time as i t does l a t e r . I t cannot be believed, however, that, ipso facto, the chick can be said to show no anxiety, or to be i n a low-anxiety state during the f i r s t few hours a f t e r hatching—given the occurrence of sudden intense changes i n the chick's perceived environment. For ease of expression, the term "sleep" w i l l be used to r e f e r to those occasions on which the chick i s l y i n g down, with head on the ground, and eyes closed, and when i t s only observable movements are breathing movements. One of Moltz's (op. c i t . ) points i s that since the animal "sleeps" f o r much of the time, i t can hardly be said to be i n a high-anxiety state. In one sense, t h i s i s quite c l e a r l y true, but i t i s also mislead-ing. Given a sleeping chick, events which would lead to anxiety responses, were i t awake, do not do so now. Even i f a chick slept for the whole of twenty-four hours, there would be no evidence that c e r t a i n events, which did not arouse anxiety i n the sleeping animal, would not do so i f the animal were awake when they occurred. There i s an alte r n a t i v e to saying that sleep indicates the absence of anxiety; that i s to maintain that sleep functions 1 5 2 to reduce the perceived environment to an extremely low l e v e l . I t i s not so much the case that the threshold f o r anxiety responses i s high, as that the perceived environment i s minimal. It w i l l be clear that these two statements are not necessarily contradictory. The f i r s t may simply imply that, at the time when the animal was going to sleep, events were not occurring which e l i c i t e d anxiety responses, while the second statement implies both that, given the sleeping animal, the occurrence of these events does not now e l i c i t these responses, and othat, had they occurred at the time when the animal was going to sleep, i t would not have slept, but would have shown anxiety responses. Referring t h i s to Moltz's two-part theory of imprinting, i t w i l l be seen that i t applies to the f i r s t part o n l y — t h e state of the animal during i t s i n i t i a l exposure to the target-object, and the e f f e c t of the target-object on the animal at t h i s stage. The most relevant portion of Moltz fs a r t i c l e begins on page 303» under the major heading "Why Following Occurs". Anxiety w i l l be defined as an i n t e r n a l emotional state of the organism, t h i s i n f e r r e d state being indexed by such observable events as d i s t r e s s c a l l s , s t a r t l e behaviour, defecation, etc. Later, he states (pp. 30*+-305): A low anxiety state can be thought of as i n -volving a p a r t i c u l a r c o n s t e l l a t i o n of v i s c e r a l and cardiac a c t i v i t i e s , some f r a c t i o n of which can become conditioned to previously neutral s t i m u l i . 1 5 3 I After discussing the ease with which birds perceive movement, he says (p. 3 0 * + ) : Although, there i s no reason, of course, to assume that s e n s i t i v i t y to movement i s greater during the c r i t i c a l period than at any other stage i n ontogeny, the f a c t that the b i r d does possess t h i s s e n s i t i v i t y at a time when i t s anxiety l e v e l i s low makes the c r i t i c a l period important with respect to the organization of the following response. I t s importance seems to be re l a t e d e n t i r e l y to the f a c t that i t provides the occasion f o r the conjunction or association of a low anxiety drive and an attention evoking object. The behaviour of the b i r d , during i t s i n i t i a l exposure, i s as follows (p. 3 0 3 ) s A duckling between 8 and 1 0 hours old when placed i n t h i s apparatus f o r the f i r s t t r i a l , usually exhibits very l i t t l e locomotion. The animal frequently drowses and appears to attend to the object only when i t passes near him. During t h i s time none of the conspicuous signs of anxiety i s present. During the second exposure: However, when the animal i s reintroduced to the apparatus 2k hours l a t e r f o r the star t of the second 25-minute test t r i a l , i t emits many d i s t r e s s c a l l s and frequently runs about the a l l e y f o r a b r i e f period before beginning to follow. Once following begins, the strength of the response i n -creases progressively u n t i l the duckling comes to devote the entire period to pursuing the test object. As long as i t remains i n close proximity to the object neither d i s t r e s s c a l l s nor s t a r t l e responses are usually emitted. Moltz's position rests on the following conditions: That the d e f i n i t i o n s of anxiety response and anxiety state are :meaningful. This implies that the behavioural indices of the anxiety state constitute an i d e n t i f i a b l e class of behaviour, separate from any other class such as eliminative behaviour, sexual behaviour, feeding behaviour, warming behaviour, etc., OR that, i f any items from these other classes constitute part of anxiety behaviour, then these appear i n a f i x e d , unique pattern defined i n terms of temporal sequence, r e l a t i v e duration, r e l a t i v e strength, or some other r e l a t i o n a l property). That the labels a f f i x e d to t h i s class of behaviour, namely, "anxiety response", "anxiety behaviour", or "anxiety state", "anxiety drive", etc., r e l a t e the observable unique pattern to the i n t e r n a l and external stimulus conditions, whose occurrence i s at l e a s t p o s i t i v e l y correlated with that of the behaviour i n question. This means that these stimulus conditions also must be i d e n t i f i a b l e and unique i n the same sense as referred to above, and that the use of the labels to r e l a t e the behaviour to the conditions i n which i t arises does not c o n f l i c t with th e i r common, or accepted usage. I f the proposed labels are new, and therefore a r b i t r a r y , or i f i t i s proposed to use them i n a novel, and therefore a r b i t r a r y , sense, some l o g i c a l j u s t i f i c a t i o n — e x t e r n a l to the r e l a t i o n i t s e l f — m u s t be presented for doing so. That the d e f i n i t i o n s so reached include every relevant item, at whichever l e v e l (e.g., neurological, or p h y s i o l o g i c a l , or 1 5 5 psychological) of discourse i s used. That the chick i s i n a low anxiety state during the i n i t i a l exposure. This means that the d e f i n i t i o n and usage of the term "low anxiety state", or a synonymous term, must meet the above three conditions, i n addition to i t being shown to be appropriate at t h i s experimental stage. That the chick i s i n a high anxiety state during the subsequent exposure (see the l a s t condition above). That the various psychological processes suggested by Moltz ( c l a s s i c a l conditioning, reinforcement learning, etc.) do, i n f a c t , occur. Since, at best, these can only be operationally defined, i t must be shown merely that a p a r a l l e l e x i s t s be-tween the procedures used and r e s u l t s found i n other cases where the terms are used, and those used and found i n the present ease. The present writer f e e l s that these conditions are not adequately met. In the f i r s t place, the present r e s u l t s indicate that d i s t r e s s c a l l s and f l i g h t behaviour are not the only indices of anxiety, and, at the same time, that these are shown by chicks when taken from the incubator within one or two hours of hatching. While the r e s u l t s do confirm that such chicks spend a good deal of time "asleep", i t has been suggested that t h i s by no means provides evidence that the animals are f u n c t i o n a l l y incapable of showing anxiety behaviour during the f i r s t day. The f a c t that, after a few hours, the chicks' locomotor a b i l i t i e s are such that ( 5 ) ( 6 ) 1 5 6 they can now show t h i s anxiety by means of f l i g h t , merely makes the task of i d e n t i f y i n g t h e i r anxiety somewhat easier. S i m i l a r l y , the f a c t that such behaviour i s more common on the second day, as Moltz found, appears to be a r e s u l t , not so much of the develop-ment of anxiety, as of t h i s increased locomotor a b i l i t y , coupled with the greater number of instances of novel stimulation which the increased locomotion brings about--in other words, anxiety i s now more e a s i l y i d e n t i f i e d and more often e l i c i t e d . Previously i t was harder to i d e n t i f y , and les s often e l i c i t e d (because the animal was asleep f o r a greater proportion of the time, and could locomote only poorly even i f awake). This would suggest that conditions 1 , 3 , and 5 } above, have not been met i n f u l l . The second part of condition 2, r e f e r r i n g to usage of labels which include the term "anxiety", need not be considered here, as the use of the term does not appear to c o n f l i c t with common usage, whether, i n t h i s usage, i t i s vacuous or substantive. This has been b r i e f l y referred to i n Chapter I. The f i r s t part of condi-tion 2 may be said to have been met, i n so f a r as r e l a t i n g the behaviour or state l a b e l l e d "anxiety" to the stimulus conditions i s concerned—at l e a s t , once the chick i s i n the runway—even though the i d e n t i t y , uniqueness and inclusiveness of what i s referred to by the term may be questioned. Since the processes postulated by psychologists to underlie behaviour (condition 6 ) are, to a great extent, a r b i t r a r y , unidentified (at the moment at l e a s t ) i n the complementary "lower" l e v e l s of discourse (e.g., 1 5 7 ) neurophysiology), and subject to revision, not only with the introduction of new data, but also with the introduction of new terms,.new meanings of terms, new attitudes, and new fashions, and since a prima f a c i e case for the presence of an operational p a r a l l e l i n t h i s instance may be made, i t i s of importance s o l e l y to examine the theory i n the l i g h t of some new elements i n the animal's behaviour, and i n i t s environment, which may be of signif i c a n c e . Before doing t h i s , however, two further aspects of Moltz's theory w i l l be considered, and two other theories, apart from th i s and Lorenz's, w i l l be stated again. Moltz c i t e s the work of Moltz, Rosenblum and Halikas ( 1 9 5 9 ) i n support of h i s hypothesis that strength of following i s r e l a t e d to anxiety. These investigators, i n e f f e c t , negatively conditioned the experimental animals to the imprinting runway by giving them e l e c t r i c shocks i n the runway, but i n the absence of the target-object. Other animals were s i m i l a r l y shocked outside the runway, or were placed either inside the runway, or outside i t , without being shocked. They found that the animals negatively conditioned to the runway (but not to the target-object) subsequently showed much greater following i n the runway than did the others. This i s hardly surprising, since, subsequently, the only stimulus i n the runway, to which the animals had not been negatively conditioned, was the target-object. The shocks were given prior to the seventh ordinary imprinting exposure ( i . e . , one 25-minute exposure on each of the preceding 6 days, commencing on the day 1 5 8 of hatching). I t i s doubtful whether t h i s r e s u l t provides any support for the hypothesis proposed. With regard to the postulated two d i f f e r e n t degrees of anxiety during the f i r s t exposure and during the second, low and high respectively, and to the conditioning (Day 1 ) and drive-reduction (Day 2) which are claimed to underlie the occurrence of following, a serious d i f f i c u l t y a r i s e s . I t w i l l be r e c a l l e d that Moltz states (p. 3 0 3 ) that, on the f i r s t exposure, a few hours aft e r hatching, the animal "frequently drowses and appears to attend to the object only when i t passes near him." The animal i s said to be i n a low-anxiety state, and t h i s low anxiety, i t i s claimed, becomes associated or conditioned to the target-object, which appears to be the only, or almost the only, part of the t o t a l stimulus s i t u a t i o n to which the animal attends. The present r e s u l t s (obtained from chicks, rather than from ducklings, which Moltz used) indicate that t h i s i s only r e l a t i v e l y so, that the animals may attend to, and show several-forms of behaviour i n , other parts of the runway, and that being'removed from t h e i r l i v i n g quarters and being placed i n the runway e l i c i t s anxiety behaviour i n them. Be t h i s as i t may, however, even i n terms of Moltz !s argument, a contradiction a r i s e s — l e t i t be supposed that the t y p i c a l b i r d does sleep, or at l e a s t drowse, during- most of the f i r s t exposure. I t would seem reasonable that the drowsy animal should be described as being i n a low anxiety state. I t would, further, not be unreasonable to say that the 1 5 9 drowsy animal did not attend to the imprinting environment, by and large, and, therefore, having attended to almost no part of i t , could have almost no part of i t associated with, or conditioned to, t h i s low anxiety state, which i t i s i n while not attending to the st i m u l i from the runway. Indeed, one has to spend large sums of money to learn while one i s asleep. But then, some sudden f l u c t u a t i o n of r e t i n a l i l l u m i n a t i o n , produced by a moving object, and greatly enhanced beyond that experienced by mammals, due to the bird's possession, i n i t s eyes, of a highly p l i c a t e d pecten projecting from the point of entrance of the optic nerve into the vitreous humour, (Moltz, p. 3 0 ^ - ) , beings the animal out of i t s slumbers. This i s the moment of conditioning. The state the b i r d i s i n , on suddenly being aroused, i s to be conditioned to the presence of t h i s arousing object. Is i t the case that these c o n d i t i o n s — t h e only ones relevant, as has been seen, to the proposed conditioning—represent low anxiety? The only r e a l l y conclusive means of determining how anxious the animal i s at t h i s time would be to measure whatever physiological changes may be shown to be r e l a t e d to or to c o n s t i -tute the anxiety state. There are two types of problem associated with t h i s , however, one p r a c t i c a l and one t h e o r e t i c a l . The p r a c t i c a l one arises i n that some recording device must be attached to the animal which i s sensitive enough to pick up the changes, which provides a record of these changes f o r analysis by the observer, which does not af f e c t the anxiety state at the time of imprinting, and which does not influence the overt behaviour of 160 the animal at that time (e.g., by requiring t r a i l i n g leads, or by being r e l a t i v e l y heavy). I t i s conceivable that, by i n j e c t i n g a radio-active dye into the animal's bloodstream—one which would remain therein u n t i l the experiment had been run—and by noting the rate at which t h i s passed through i t s heart, one could achieve the desired data. This would avoid such problems as t r a i l i n g leads etc., since the recording equipment need not then be attached to the animal, and need only pick up the changes i n the motion of the dye as i t moved through the heart. One could not k i l l the animal and check i t s hormonal balance, since t h i s would be affected as i t was being caught and k i l l e d , and i n any case, ther! kind of measurement required must be available during subsequent t r i a l s . In the absence of such data, and even ignoring the present evidence, i t seems unlikely that what i s conditioned to the arousing (target) object i s low anxiety. I f anything, the animal would appear to be momentarily i n a r e l a t i v e l y high anxiety state. Since i t i s i n t h i s moment that the conditioning takes place, the stated f a c t that the animal i s drowsy, and therefore i n a r e l a t i v e l y low anxiety state, f o r the r e s t of the time.is e n t i r e l y i r r e l e v a n t . The t h e o r e t i c a l d i f f i c u l t y with such ph y s i o l o g i c a l recording i s that i n order to show that any given measure i s an index of anxiety, one has to at least show that i t i s very highly p o s i t i v e l y correlated with overt behaviour which i s known with c e r t a i n t y — f o r reasons external to the physiological r e c o r d i n g s — t o 161 | r e f l e c t anxiety. This does not arise with humans as subjects, for they can indicate verbally when they f e e l anxious, with some degree of accuracy, one has to assume. The problem i s to decide, i n the case of lower animals, which behaviour pattern, or which items, r e f l e c t anxiety. Moltz*s l i s t (see above) included "distress c a l l s , "startle behaviour, defecation, etc." I t has already been argued that emotion should not be "read i n t o " s t a r t l e behaviour, when i t i s observed i n neonates, at l e a s t , and defecation measures have been questioned on other grounds. Despite the previously mentioned f a c t that the birds* c a l l s vary along various continua, as judged by the human ear rather than as measured by the spectrograph, and that the c a l l s of one b i r d may not be so loud as those of another, i t i s admitted that the loud, sharp, almost ear-shattering c a l l s of chicks do appear to be dis t r e s s c a l l s . Unfortunately for Moltz rs analysis, the chicks used i n thi s study almost i n v a r i a b l y gave these c a l l s when only a few hours old, and during the f i r s t exposure—the time when Moltz claims that t h e i r anxiety i s low. I t may very well be that these w i l l be shown to be rela t e d to such factors as heat l o s s , and that the term anxiety—under these c o n d i t i o n s — i s too global to be useful. What can probably be said i s that when these "concrete" conditions are i n e f f e c t (e.g., when the animal i s cold),these constitute anxiety. Not only have the items included i n Moltz*s d e f i n i t i o n of anxiety been questioned, and not only have these been found to occur i n newly-hatched chicks (which i 162 refutes the proposed theory), but also i t has been suggested that the chick i s aware of f a r more of the runway than simply the target-object. What appears to be the case i s that whenever (at least at f i r s t ) the target-object comes close to the animal, i t i s alerted to a greater degree than when the target-object i s distant. I f one pictures a. graph, p l o t t i n g anxiety-level against time, Moltz's p o s i t i o n would seem to mean that a more or less straight l i n e , s t a r t i n g and remaining at a low l e v e l on the anxiety axis, and therefore running close to and p a r a l l e l with the time axis, could be drawn on that graph to indicate the chick's anxiety l e v e l during the i n i t i a l exposure. The present sugges-t i o n "is that such a l i n e would be accurate f o r the greater part of the time, but that sharp peaks would be needed to represent the very b r i e f , but c r u c i a l l y important, moments when the moving target-object passed close to the animal. Since the sum of a l l these moments would constitute a r e l a t i v e l y small proportion of the t o t a l time, the o v e r a l l "general" l i n e would s t i l l indicate low anxiety, but r e l a t i v e l y high anxiety would have to be claimed as being the state which was conditioned to the presence of the target-object. I t i s i n t e r e s t i n g to note that, i f such were the case, Moltz*s analysis would hardly need modifying. I f i t i s remembered that this'anxiety i s said to be caused by the animal's perception of novel s t i m u l i (Moltz, p. 3 0 5 ) , then the analysis could be modified to read as follows: 163 On the f i r s t exposure, the animal attends only to the target-object, and then only when i t i s near him. This means that the novelty of the target-object arouses momentary high anxiety, and t h i s i s what i s conditioned to that stimulus. I t cannot show t h i s anxiety i n the most obvious fashion since i t cannot run ( f l e e ) to any great extent. On the second exposure, the animal attends to many other features i n the runway, as well as the target-object. These other features are being attended to f o r the f i r s t time, and therefore e l i c i t high anxiety. The target-object, however, i s being attended to f o r the second time, and, by d e f i n i t i o n , i s le s s novel. I t therefore e l i c i t s somewhat less anxiety than the re s t of the runway does. (N.B. During the f i r s t exposure, the target-object captures the attention of the animal many times, not just once. In the present experiment i t did so roughly once every t h i r t y seconds f o r a period of about 1 5 minutes.) Thus, as Moltz suggests, i f the animal i s near the target-object, t h i s serves to reduce i t s anxiety on the second exposure. On each subsequent occasion, the target-object w i l l have been attended to more often than w i l l the r e s t of the runway, hence i t w i l l always be l e s s novel and have the advantage as a r e i n f o r c e r . The c r i t i c a l period i s s t i l l accounted for i n terms of Moltz's analysis, so need not be discussed again. T h e o r e t i c a l l y , one could argue that the present suggestions do not even require the introduction of any form of learning—although t h i s would only 161+ end i n semantic discussion. The only postulates needed are two— an anxiety response to novel s t i m u l i , and memory. Since, i n conventional terms, one would say, "The animal has learnt to follow the target-object," a compromise might be effected i f learning were taken simply to describe (not explain) a class of events. Used i n this capacity, the term would not imply a neurological or any other change within the s u b j e c t — t h e only such change would be implied by the term "memory". The reason why i t was suggested e a r l i e r that the only conclusive test of Moltz's anxiety theory would require physio-l o g i c a l measures i s that, although the present analysis seems more appropriate to the behaviour of the chicks, the same evidence which supports Moltz's theory also supports t h i s one. The position i s awkward i n that i f the animal's anxiety i s made to increase during the f i r s t exposure to the runway, at the moments when i t i s attending to the target-object, then, i n e f f e c t , the animal w i l l have been negatively conditioned to the target-object. Conversely, i f the animal|s anxiety i s decreased at these v i t a l moments, then the animal w i l l remain asleep, or drowsy (as Moltz claims i t does fo r the r e s t of the time), and w i l l not notice the target-object. I t seems very s i g n i f i c a n t that several animals, towards the end of the f i r s t exposure i n the present experiment, having at f i r s t paid attention to the target-object when i t was near them, then lay down and apparently slept, paying l i t t l e further attention to the target-object. Since the 1 6 5 only e s s e n t i a l difference between the present analysis and Moltz's concerns the i n i t i a l exposure, the behaviour of these animals appears to support t h i s analysis rather than the former. The other two theories which should be mentioned again before suggesting a factor which appears to reconcile both them and Moltz's theory are those of Hess ( 1 9 5 6 / 5 7 ) concerning energy expenditure, and of Hinde, Thorpe, and Vince ( 1 9 5 6 ) , Hinde ( 1 9 5 5 ) > and Hess ( 1 9 5 9 ) . Hess ( 1 9 5 6 / 5 7 ) obtained r e s u l t s which seemed to indicate that the strength of the following response was a function of the e f f o r t expended i n following. Length of exposure was not the c r u c i a l f a c t o r , and i f obstacles were placed i n the bird's path, such that greater energy was expended i n crossing them, distance followed was not necessarily the only index of energy expended. The other theory i s similar to Moltz rs, but was not f u l l y developed. I t states that the c r i t i c a l period depends upon two f a c t o r s — t h e a b i l i t y to locomote, which develops with age, and the onset of fear reactions. Heat loss/heat production, i t i s thought, provides an opportunity f o r synthesis. I t i s assumed that when an animal i s cold, several autonomic changes occur which s>^veito • f a c i l i t a t e the retention of whatever heat i t has, as well as to increase i t s heat production. Shivering and movement, i n p a r t i c u l a r , w i l l restore the body's heat. To the writer's knowledge, Imprinting experiments, whether i n the f i e l d or i n the laboratory, have not been held under conditions i n which the temperature was the same 1 6 6 i n the animal's l i v i n g quarters and i n the runway (or test area). While one i s ca r e f u l to ensure that the newly-hatched b i r d has hot l i v i n g quarters (e.g., i n an incubator), one usually does" not i n s i s t that the runway be maintained at the same high tempera-ture. Even i f the study i s a f i e l d one, and the day i s hot., the animal i s provided with some form of extra heat i n i t s l i v i n g , quarters. In the present experiment, f o r example, the animals 1 boxes were placed very close to a large ra d i a t o r , while the runway was some distance from there. (N.B. This fa c t o r did not emerge u n t i l after the experiments, and observations had been completed). The "non-imprinting" chicks were placed i n a pen i n which the temperature under the lamp was 1 0 degrees higher than i t was some f i v e or six feet away, and these animals remained under, or near the lamp for most of the time, p a r t i c u l a r l y on the f i r s t day. The hens, i t w i l l be r e c a l l e d , remained at the f a r end of the pen,for most of the time. Now the hens were well supplied with feathers, and the body temperature of a broody hen r i s e s s l i g h t l y above i t s l e v e l when the hen i s not broody, whereas the chicks had only an inadequate supply of down, which by no means covered t h e i r bodies, and which was s t i l l damp i n many cases when the birds were removed from the incubator. These are the ones who would f e e l the cold most strongly. I t has also been established that newly-hatched chicks give d i s t r e s s c a l l s when they are cold (pp. 2 2 - 2 3 above), and di s t r e s s c a l l s , i t has been concluded, provide the surest i n d i c a t i o n of anxiety. In 167 order to become cold, the non-imprinting chicks had to move from where they were placed under the lamp. They did t h i s , from time to time, even on the f i r s t day, but did not give dis t r e s s c a l l s . I t i s suggested that they did not do so because, i n f a c t , they did not become cold when away from the lamp due.to the f a c t that they had to use their muscles to stand up and to move away from the lamp. They moved around almost continually when away from the lamp, pecking at the ground and preening from time to time, and then lay down again under the lamp. The "chicks who were used for the a r t i f i c i a l imprinting, on the other hand, were taken from a higher to a lower tempera-ture, and l e f t there with no d i r e c t heat source. Almost without exception, they stood or lay down fo r about 10 seconds, then began c a l l i n g s o f t l y , stood up i f they were l y i n g down, moved around and c a l l e d loudly and continually. In some cases the "gock" recording caused t h i s c a l l i n g to cease, which can hardly be accounted f o r i n terms of heat production, i t i s granted, but i t i s not suggested that heat loss/heat production i s by any means the only relevant f a c t o r — m e r e l y that i t i s an important one which has been overlooked to some extent at l e a s t . In most cases the birds continued th e i r d i s t r e s s c a l l s u n t i l the target-object began to move, when they moved i n towards i t and with i t for a short distance. Now i f the animals were cold, as they almost c e r t a i n l y were, t h i s movement would serve to produce heat. The problem s t i l l remains as to why they should attend to the target-1 6 8 object i n the f i r s t instance. I t i s suggested that t h i s response i s comparable to the s t a r t l e reaction previously described and discussed. I t i s probably of a r e f l e x nature, and i s e l i c i t e d by r e t i n a l f l i c k e r . I t would probably best be c l a s s i f i e d as an elementary component of c u r i o s i t y or exploratory behaviour, rather than as an anxiety response. Whereas the s t a r t l e response i s usually given i n situations which lead to some form of r e l a t i v e l y d i s t r e s s f u l treatment (cf. the behaviour of the experienced hens, as opposed to the naive chicks), and therefore soon becomes an anxiety response, c u r i o s i t y behaviour, although i t may start as a similar r e f l e x response, develops i n those situations i n which the e l i c i t i n g stimulus (a) persists at l e a s t for a short while, (b) remains at about the same i n t e n s i t y , and (c) does not lead to d i s t r e s s f u l treatment. Once the e l i c i t i n g stimulus loses i t s novelty, the response may be expected to decline, or other responses may take i t s place (e.g., i n t h i s case, i f following the target-object has been p o s i t i v e l y r e i n f o r c i n g , t h i s may be the form i n t o which the response w i l l develop). Berlyne's work ( 1 9 5 1 ) centres upon t h i s c u r i o s i t y or exploratory fa c t o r . Coupled with these two f a c t o r s , temperature and explora-t i o n , i s the f a c t that at an age of a few hours chicks do not locamote well . This would account for t h e i r r e l a t i v e l y poor following on the f i r s t day (see Chapter I I I above, and Moltz., I 9 6 0 ) . The energy expended by these chicks on the f i r s t day, 1 6 9 however, may well be equal to or greater than that expended on the subsequent days when they follow more continuously. I t i s probable that even to maintain i t s head at medium height i n front of i t s body, even to remain standing, even to simply turn towards the moving target-object, requires, at t h i s age, a tremendous amount of e f f o r t . This i s where Hess's e a r l i e r f i n d i n g ( 1 9 5 6 / 5 7 ) i s r e l e v a n t — t h e e f f o r t expended i n maintaining i t s orientation towards the target-object as i t moves past r e s u l t s i n increased heat production, which serves to reinforce the behaviour i n ' question. Since, on subsequent occasions, the chick i s d r i e r , i t s down provides a more adequate insulator for i t s skin, and i t s developing muscles enable i t to move with le s s e f f o r t , i t would have to be postulated that the o r i g i n a l l y r e i n f o r c i n g behaviour now continues as a habit somewhat les s dependent upon the r e i n -forcement than i n i t i a l l y , were a complete theory being developed here. This i s not the aim of the present discussion. The writer merely wishes to bring to attention a factor whose importance, appears to have been overlooked i n analyses of the animal's behaviour i n the imprinting s i t u a t i o n . At the same time, such a suggestion must be put forward since i t appears to underlie both the anxiety and energy-expenditure theories, and therefore deserves, at the very l e a s t , to be put to experimental t e s t . This can r e a d i l y be done, of course, by varying the temperature i n and around the runway, and between the animal's l i v i n g quarters and the runway. I f t h i s factor turns out to be unimportant, at 170 l e a s t i t w i l l not need to be raised again, and the f a c t that i t provides a common basic element which appears to underlie both groups of theories must be put down to coincidence. I t has . already been introduced i n connection with the behaviour of Harlow monkeys (Chapter I above) and when applied i n t h i s fashion i t does appear to be more than t r i v i a l , which i t was f i r s t thought to be by the writer. Whether or not t h i s factor turns out to be important, i t does represent the sort of thing which must be sought out i f explanations of t h i s type of behaviour are to progress from stating correlations to showing causes. The question must be asked: What causes the anxiety? What makes the animal give d i s t r e s s c a l l s i n t h i s situation? How i s i t that the expenditure of energy leads to the development of stronger following? The answer to these questions must come from many complementary d i s c i p l i n e s . The behaviourist may be content to show that a r e l i a b l e c o r r e l a t i o n e x i s t s at h i s l e v e l of discourse, but the physiologist, the neurologist, the h i s t o l o g i s t , as well as the neuro-chemist and the embryologist, w i l l not rest u n t i l they have gone beyond the c o r r e l a t i o n to the underlying cause. . 171 CHAPTER V SUMMARY AND CONCLUSIONS The l i t e r a t u r e relevant to imprinting has been reviewed. It has been suggested not only that explanation of the behaviour remains somewhat elusive, but also that the behaviour has been inadequately described. The present observations indicate that following i s but one s i g n i f i c a n t aspect of the animal's behaviour i n an imprinting s i t u a t i o n . Several other features have been examined, including heat production and maintenance, and what i s best classed as c u r i o s i t y or exploratory behaviour. Evidence has been provided that behaviour i n response to d i s t r e s s f u l conditions—normally r e f e r r e d to as anxiety behaviour—appears i n the chick from the time when i t i s f i r s t removed from the incubator soon after hatching. Stress has been l a i n on the necessity f o r more intensive analysis of the factors which lead to what i s termed anxiety, and of the ways i n which the animal i n the imprinting s i t u a t i o n responds to these f a c t o r s . Attempts have been made to present the si t u a t i o n as the animal experiences i t , which i s f e l t to be the prerequisite of any explanation. In a non-imprinting s i t u a t i o n , the behaviour of newly-hatched chickens i n various groups was found to contain many forms, which were common to a l l the animals. The general develop-ment of behaviour was found to follow a similar pattern i n each group. A number of i n d i v i d u a l and group differences were found, 172 however, which were correlated with differences i n the stimulus conditions between those groups. The more young chickens (ranging i n number from one to four) there were i n a group, the greater was the duration of a c t i v i t y of the members of that group between t h e i r r e s t periods. An exception to t h i s occurred i n the group of two newly-hatched chicks alone i n the observation pen— this group was f a r more active than most of the others, equalling the a c t i v i t y of the four-member groups. The presence of a broody hen attracted a c e r t a i n amount of the c h i c k s 1 a t t e n t i o n — t h e y watched the hen, and approached her, running beneath her body.. The more chicks there were i n a group, the l e s s t h i s happened. The hen attacked the approaching chicks, pecking them v i c i o u s l y , and throwing them from her. In the case of the single chick with the broody hen, t h i s happened over f i f t y times during the f i r s t day on which they were together, then, when the observer returned the next day, the hen was brooding the young chick, and continued to do so throughout that day. In no other case did a hen brood any chicks, and i n no other case did the chicks approach the hen more than about 10 times i n the two-day period. Chicks i n groups, as opposed to a single chick, oriented almost a l l t h e i r behaviour towards each other. They showed two forms of behaviour i n p a r t i c u l a r , which the single chick did not (and could not) show—mutual preening and huddling together. < One chick of a group of several would not remain apart from the group f o r more than a few seconds—except i n one group of three, where two of the 173 chicks appeared to be r e s i s t i n g the approaches of the t h i r d (unless they were l y i n g beneath the lamp). As chicks grow older they become more active, remain active f o r longer periods, and venture further from a heat-source. For the f i r s t few hours their locomotor a b i l i t i e s are poor, and they spend a good deal of time l y i n g near a source of heat.. Their movements at t h i s stage are badly controlled; their balance i s poor. On the f i r s t day out of the s h e l l they eat l i t t l e and defecate l i t t l e ; on the second day both these forms of behaviour increase i n frequency. Distress c a l l s may be given not only from the time of hatching, but also while the chick i s s t i l l i nside the egg. Head and mouth movements are almost continuous within the egg. As the chicks grow older, they become d r i e r , and their down becomes t h i c k e r — a t f i r s t i t i s damp, and barely covers t h e i r skin. A clear-cut s t a r t l e response i s given, at a l l stages, upon the occurrence of a sudden intense change i n auditory stimulation. This occurs l e s s commonly when the chick i s apparently sleeping than i n one of i t s active periods. At several hours of age the chicks f l e e from a novel auditory and v i s u a l stimulus, which i s presented suddenly"and intensely (a hose i s pushed across the wire-mesh walls into the cage as a means of replenishing the water at the end of the f i r s t day). A l l these forms of behaviour are thought to be relevant to an analysis of the processes under-l y i n g imprinting; almost a l l of them are shown In the imprinting runway, and the chicks struggle, peck, run, and c a l l as the experimenter reaches into t h e i r i l i v i n g quarters to remove them 17k and carry them to the runway, when they are a few hours old. Several theories of imprinting are examined i n the l i g h t of the observations. Emphasis i s l a i d on the stimulus conditions, the physiological state of the animal, and i t s behaviour, from before i t hatches u n t i l i t i s exposed to the imprinting apparatus, and during the exposure(s). Heat-producing behaviour and c u r i o s i t y behaviour are stressed i n connection with these theories because they appear to have been overlooked, and, at the same time, provide a common element which may underlie these theories. An analysis i n these or similar terms, i t i s suggested, w i l l pave the way for the establishment of the cause or causes of the behaviour i n question, and to t h i s end the co-operation of the various other b i o l o g i c a l d i s c i p l i n e s i s invoked. 1 7 5 REFERENCES 1 . A l l e y , R., and Boyd, H. Parent-young recognition i n the coot. I b i s . 1 9 5 0 , 9 2 , * f 6 - 5 l . 2 . Andrew, R.J. Some remarks on c o n f l i c t s i t u a t i o n s , with special reference to Emberiza spp. B r i t . J. anim. 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