UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

The isolation of certain experimental issues in the continuity controversy Levey, Archibald Banks 1953

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-UBC_1953_A8 L3 I8.pdf [ 6.55MB ]
Metadata
JSON: 831-1.0106474.json
JSON-LD: 831-1.0106474-ld.json
RDF/XML (Pretty): 831-1.0106474-rdf.xml
RDF/JSON: 831-1.0106474-rdf.json
Turtle: 831-1.0106474-turtle.txt
N-Triples: 831-1.0106474-rdf-ntriples.txt
Original Record: 831-1.0106474-source.json
Full Text
831-1.0106474-fulltext.txt
Citation
831-1.0106474.ris

Full Text

THE -ISOLATION OF CERTAIN EXPERIMENTAL ISSUES IN THE  CONTINUITY CONTROVERSY by ARCHIBALD BANKS LEVEY A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS i n the Department of PHILOSOPHY AND PSYCHOLOGY We accept t h i s thesis as conforming t o the standard required from candidates for the degree of MASTER OF ARTS Members of the Department of Philosophy and Psychology. THE UNIVERSITY OF BRITISH COLUMBIA October, 1953 THE ISOLATION OF CERTAIN EXPERIMENTAL ISSUES IN THE CONTINUITY CONTROVERSY Abstract The h i s t o r i c a l development of the continuity controversy i n discrimination learning i s reviewed i n i t s essential aspects as a th e o r e t i c a l and as an experimental problem. Some implications of the controversy are d i s -cussed and an analysis i s made of the trends of experiment-a l evidence t o date. I t i s found that, i n experiments i n which a r e l a t i v e l y simple discrimination i s tested, the continuity position i s generally upheld, while i n complex discriminations the issues remain i n doubt. A f a i r l y de-t a i l e d statement of each of the t h e o r e t i c a l positions i s presented i n an e f f o r t to c l a r i f y the experimental issues and t o a r r i v e at c r i t e r i a which are offered as being ess e n t i a l f o r experiments directed at the controversy. The design of such an experiment i s presented. This ex-periment could not be completed and the possible causes of i t s f a i l u r e are analysed. In the absence of f i n a l r e s u l t s the data fo r the i n i t i a l brightness discrimination are'analysed and found to y i e l d s i g n i f i c a n t results i n favour of the continuity theory. I t i s suggested that i f experiments which meet the c r i t e r i a a r i s i n g out of the re-quirements of both the theories are repeatedly found to be inoperable or inconclusive the controversy i n i t s present form cannot be held to have operational meaning. Areas of the controversy i n which further c l a r i f i c a t i o n of theory i s needed are indicated. References are included which of f e r a balanced survey of the l i t e r a t u r e . ACKNOWLEDGMENT The writer wishes t o express his gratitude to the Department of Philosophy and Psychology, U.B.C., for i t s generous provision of equipment and f a c i l i t i e s , and to those f a c u l t y members who contributed c r i t i c i s m s and suggestions. Thanks are p a r t i c u l a r l y due to Dr. D. T. Kenny whose stimulating presentation of i t s issues i n i t i a t e d t h i s study and who acted as i t s advisor; and to Prof. E. S. W. Belyea, who ki n d l y f a c i l i t a t e d con-s t r u c t i o n of the apparatus and provided the photographs. Thanks are also due to Dr. A. J. Wood, Department of Animal Husbandry, U.B.C., who graciously extended the loan of cages and equipment and offered advice on the caging and general economy of the colony. C O N T E N T S Chapter Page I Introduction 1 I I H i s t o r i c a l background of the controversy 5 Theoretical issues 5 — Experimental issues 15 Recent trends 26 Summary 34 I I I C l a r i f i c a t i o n of the two positions 36 The continuity position 36 The non-continuity p o s i t i o n 41 IV The Experiment 48 C r i t e r i a for an adequate experiment 48 Rationale of the present experiment 52 Apparatus 56 Controls 58 Plan of procedure 60 Description of procedure 65 Analysis of possible causes of f a i l u r e 69 V Results 72 Descriptive analysis of data 72 Analysis of error scores 76 The Spence assumptions 94 VI Summary and conclusions 99 References 103 T A B L E S Possible dispositions of error scores for given categories of p o s i t i o n re-sponses P r o b a b i l i t y of chance occurrence of the error scores presented i n Table I Performance of each subject i n block of ten t r i a l s Frequency of occurrence of possible error scores permitted by the occur-rence of 9, 8, or 7 position responses i n ten t r i a l s Theoretical and observed d i s t r i b u t i o n of error scores during three phases of the pre-solution period Di s t r i b u t i o n of error scores i n the t h i r d and fourth quarters of the pre-solution period for Category 7 P L A T E S Plate Page I Stimulus windows and double pronged 57 jumping stand I I Goal box and alternate non-reward 59 compartments I I I Apparatus from i n front 61 IV F i n a l stimulus cards with an animal 64 approaching CHAPTER I INTRODUCTION The a c t i v i t y of the rat i n i n f i l t r a t i n g contemporary psychol-ogy, and i n winning or usurping there a rather comfortable niche i n the hierarchy, i s a subject of s u f f i c i e n t dispute that the w r i t e r of a r a t thesis must f e e l impelled, before turning to his proper study, to c l a r i f y his allegiances i n the matter. Perhaps not the l e a s t appropriate means of doing t h i s i s to present the aims of such a study, together with the biases or f o c i of int e r e s t which may have prompted them. A f i r s t aim of the present study was to attempt t o assess at f i r s t hand some aspects of the r o l e of rat studies i n psychology. In doing t h i s the interest was l i m i t e d to the type of study i n which rats are used as the instruments of systematic theory. This i s the area i n which objects of the "many variable" type are naive, since such systems are not intended as l i v e descriptions of r a t behaviour; rather, the unit i s an abstract quantitative r a t analogous to the w e l l known colourless tasteless odourless b i l l i a r d b a l l of c l a s s i c a l physics. Variables which are not chosen as referents i n the theory are of no consequence other than f o r t h e i r masking effect, a purely operational problem. At present such theories provide only a l i m i t e d model for a systematic psychology. Whether they may subsequently be extended as a basis f o r psychology, or whether they must eventually be abandoned as inappropriate i s a question 2 f o r the future and any speculation i n either d i r e c t i o n i s merely an ex-ploration of biases. The s i t u a t i o n may be analogous to that of a r i g o r -ous physical science which i s l i m i t e d , however v a l i d , to producing machines which must operate at practical rather than theoretical e f f i c i e n -cy; the question f o r psychology being whether the e f f i c i e n c y attainable f o r a complex f i e l d i s s u f f i c i e n t to j u s t i f y the elaboration of theory required by such a f i e l d . On the other hand i t may prove to be the case that the understanding of i p s e i t y or uniqueness i s more fundamental to the science than inc l u s i v e systematization or i n other words that a new d e f i n i t i o n of science may be required. The i n t e r e s t here however i s i n attempting t o assess the p r a c t i c a b i l i t y of such limited-variable models by sustained observation of t h e i r processes of data formation. A second aim i n undertaking the study l i e s w i t h i n the consider-ations outlined above. Granted the l i m i t a t i o n which was imposed, there s t i l l remains the question of alternative approaches to system building. Interest i s centered here on the molecular versus "molar" pseudodichotomy which appears i n contemporary theory. One or two observations may not be amiss. F i r s t i s the obvious, but sometimes neglected, empirical fact that a molecular theory must deal at some point with molar u n i t s , together with the l o g i c a l necessity that a molar theory assume molecular processes, both emphasizing the r e l a t i v i t y of the terms. Second i s the less obvious empirical fact that at some point i n the construction of an axiomatic, deductive, or algebraic system (which at present can be equat-ed with "molecular" theory i n psychology) there must enter a factor of a r b i t r a r y or value based judgments. This i s the point at which referents 3 are chosen to produce an "interpreted" system. While t h i s type of sys-tem i s extremely impressive, i t s very awesomeness tends to overshadow the a r b i t r a r y mechanisms involved i n choice of referents. As an example Woodger's use of the method, which i s perhaps more conservative than that of H u l l , involves as a quantified variable i n i t s application to embryo-logy, the thickness of the microtome s l i c e , a convenient quantification and one which i s j u s t i f i e d but one which i s t o t a l l y a r b i t r a r y i n terms of the natural phenomena investigated. I t i s axiomatic that the description of nature provided by any theory i s r i g i d l y confined to the in t e r p r e t i v e categories which i t contains. This introduces the in t e r e s t i n g problem of possible "culture binding" i n the choice of referents. The choice of the central concept "drive" ( i . e . , motivating force) i n a culture dominated by the Faustian motif of s t r i v i n g , might for example i n a culture emphasizing an Apollonian s t a b i l i t y never be u t i l i z e d . (A con-cept, i n c i d e n t a l l y , which seems to move away from the culture bound determinants of Hull and others may be Schroedinge's "negative entrophy".) While these considerations may seem f a r a f i e l d they are by no means im-pertinent to the broader aspects of the study. A further aim then of that study was to attempt, bearing i n mind the suggestions above, an evaluation of these two approaches. The problem selected i s one of the few i n which these approaches come d i r e c t l y i n contact and are at v a r i -ance, and while the s p e c i f i c issues can determine nothing about the use-fulness of the approaches, they can shed considerable l i g h t on the manner i n which they have been applied to Learning Theory. I t was f e l t that a f i r s t hand comparison of the two modes of description could not help but 4 be f r u i t f u l , and i t i s of i n t e r e s t that the writer, who began with a strong molar bias, gradually found himself acquiring an appreciation of the molecular approach, while at the same time deepening his understand-ing of the molar a t t i t u d e . A more immediate and p r a c t i c a l aim was that of acquiring a basis on which to evaluate the growing l i t e r a t u r e of r a t studies, par-t i c u l a r l y i n view of the naive but a t t r a c t i v e temptation to generalize to human behaviour, as w e l l as the more formal application of t h i s pro-cess at a sophisticated l e v e l . I t was not hoped that a single ex-periment, however protracted, would accomplish t h i s e f f i c i e n t l y ; rather that i t would provide a matrix of observations which could serve as a foundation f o r evaluation, i f only as a substitute for that thorough saturation of knowledge essential to understanding. F i n a l l y , and most immediate, was the aim of studying the s p e c i f i c problems of the continuity controversy, together with the adm of acquiring an experimental technique i n a c l e a r l y defined area. This aspect of the study was rewarding but f e l l f a r short of y i e l d i n g con-clusive r e s u l t s . However, the writer wishes to point out that accom-panying the sparse record of the experiment i t s e l f i s a y i e l d which owing to i t s subjective nature does not appear on the typewritten pages, but which represents rewarding experience accrued, and goes some con-siderable distance toward f u l f i l l i n g the aims here outlined. CHAPTER I I HISTORICAL BACKGROUND OF THE CONTROVERSY Theoretical Issues Before turning to the h i s t o r i c a l background of the continuity controversy i t would seem appropriate to examine b r i e f l y the issues involved, and to delineate the opposing points of view. The "continu-i t y " position may be b r i e f l y stated thus : the learning process i s a gradual and continuous summation of increments to the excitatory or i n -h i b i t o r y value of cue s t i m u l i following upon reward or non-reward of each response to those s t i m u l i . The opposing viewpoint, the "non-continuity" position describes the learning process as being i n part a function of the organism's a c t i v e l y structuring the stimulus s i t u a t i o n , such that i t s performance i s dependent not only upon past experience, ^ but also upon i t s contemporary organisation of the s i t u a t i o n , rewards being e f f e c t i v e i n determining the appropriateness of a given stimulus organisation. I t would probably be unwise to conclude at t h i s point that either view involves a more extensive array of assumptions than does the other; however, i t w i l l r e a d i l y be seen that the former position i s more susceptible of concise formulation than i s the l a t t e r . While these tentative summarisations are stated i n terms of the broad issues of learning theory, the continuity controversy has i n fac t been l i m i t e d f o r the most part to the study of discrimination 6 learning. The problem i s h i s t o r i c a l i n the sense that i t has developed with a certain consistency through experimental studies and theo r e t i c a l a r t i c l e s during the past twenty-three years. The procedure here w i l l be, f i r s t , to trace t h i s development i n terms of the t h e o r e t i c a l issues which have contributed to i t , and then to examine the experimental l i t e r a t u r e insofar as i t i s pertinent, before considering the controversy as i t appears to-day. In view of the frequent overlapping of a r t i c l e s i n the journals, the treatment w i l l be l o g i c a l , rather than chronological, i n the i n t e r e s t of c l a r i t y . The "continuity controversy" was conceived, so to speak, by Lashley (26) i n 1930 ( i t was not delivered by Spence u n t i l 1936, and was christened by Krechevsky i n 193S) when he wrote i n part, . . . i n the discrimination box, responses to position, to alternation, or to cues from the experimenters' movements usually precede the reactions to the l i g h t and represent attempted solutions which are within the rat's customary range of activity....(Evidence) strong-l y suggests that the actual association i s formed very quickly, and that both the practice preceding and the  errors following i t are i r r e l e v a n t to the actual form-ation of the association.-^ Elsewhere i n the same source he refers to the " a l l or nothing basis of the discrimination habit"• The assumptions underlying these statements form the core of the non-continuity hypothesis. Krechevsky was d i r e c t l y stimulated by the foregoing statements to perform a series of experiments (15) (16) (17) designed to test these I t a l i c s mine. 7 assumptions, his method being to analyse the i n d i v i d u a l learning curves of his subjects i n terms not only of the percentage of "correct" responses but also the percentage of l e f t going, r i g h t going, alternating responses, etc. That i s , by assuming that no response was due to chance, he was able to analyse i n d i v i d u a l performances as though the animals were attempt-i n g systematic solutions, and thus to plot curves f o r the performance i n terms of these solutions. I t i s of some h i s t o r i c a l i n t e r e s t that Krechevsky was the f i r s t to use the i n d i v i d u a l curve as a the o r e t i c a l u n i t of learning. While the t y p i c a l curve f o r discrimination learning follows the chance l i n e (50$) f o r approximately three quarters of i t s length, the curves plotted as described above revealed clear cut descent from the chance l i n e during the early t r i a l s f o r the"attempted solutions", followed by a return to chance and the descent of the error curve to zero. The c r i t e r i o n set for performance beyond chance was arrived at by comput-ing the standard deviation f o r the t o t a l number of responses and exhaust-zone l i m i t thus established was assumed by Krechevsky to l i m i t the range of chance responses, and any curve f a l l i n g outside i t was taken to i n -dicate the operation of a systematic response. The tautalogy inherent i n t h i s method, which assumes no chance responses, was redeemed by com-bining the scores f o r a l l types of responses, which usually f e l l close to 100$. ( I t might, on the other hand, be held that t h i s procedure merely demonstrates that the selection of imputed "hypotheses" had ex-hausted the possible response combinations.) The experiments on which his conclusions were based were per-formed with r a t s i n the multiple choice problem box designed by Stone. i n g the chance d i s t r i b u t i o n with the formula The chance 8 Brightness and hurdle discriminations were employed, the l a t t e r to meet the Gestalt contention that there should be some necessary r e l a t i o n between stimulus and response i n any problem designed as a paradigm of the learning process. The experiments included one i n which the "prob-lem" was insoluble. Krechevsky concluded that behaviour i n a novel s i t u a t i o n i s "systematic", "purposive" ( i f . . . t h e n ) , involves "abstract-ion", and i s "not e n t i r e l y dependent on the immediate environment". Each of these terms was operationally defined, the author wishing specif-i c a l l y to avoid a mentalistic interpretation (15 )• The systematic responses were l a b e l l e d "hypotheses", and t h i s concept was further developed by Krechevsky i n l a t e r a r t i c l e s (18) (19) (20) (21) i n which the "docile" nature of the animal and the " l a b i l e " character of the response were emphasized. I t w i l l be seen that at t h i s point the "continuity controversy", though not yet so defined, centered on the issue of random versus system-a t i c responses. Krechevsky seems to have made the error of assuming that by demonstrating the f i r s t proposition of Lashley's assertion he had also proven the second. Spence (40) c l a r i f i e d the issue i n 1936 by pointing out that no sophisticated t r i a l and error theory would postulate purely random responses, and that the "systematic" behaviour observed by Krechevsky was not incompatible with t r i a l and error theory. He provid-ed an elegant demonstration of t h i s by presenting a table of hypothetical responses based on the assumption that each reinforcement of an S-R con-nection produces an increment to habit strength as a function of the ogi v a l curve postulated by H u l l , and that each non-reinforcement produces 9 a decrement which i s i n l i n e a r r e l a t i o n to i t s habit strength. I t was also assumed that the t o t a l excitatory potential of a stimulus configur-ation i s the sum of i t s component excitatory values, and that i n the case of antagonistic responses, the greatest habit strength would p r e v a i l . These are e s s e n t i a l l y the basic assumptions of the continuity hypothesis. Through them i t i s easy to demonstrate that i n the discrimination learn-in g s i t u a t i o n (a) the correct and hence i n v a r i a b l y rewarded response w i l l eventually dominate, and (b) that depending on the frequency with which another component of the stimulus configuration i s associated with the correct one, i t may acquire excitatory p o t e n t i a l s u f f i c i e n t so that the animal w i l l appear for a time to respond to i t alone. The animal's behaviour, f a r from being "purposive" or "systematic", i s determined by the combined effects of the habit strength associated with each stimulus component and the order of presentation of the s t i m u l i themselves. One of the deductions which Spence drew from his assumptions was that i f the reward relations of a given p a i r of s t i m u l i were reversed p r i o r to the ac q u i s i t i o n of the discrimination by the animal, i t s learning i n the subsequent t r i a l s would be retarded. A reservation was imposed that the "connection between the relevant stimulus and the required motor response" must be " s u f f i c i e n t l y obtrusive and clear to the animal". The reversed pre-training experiment thus suggested was performed by members of each group with c o n f l i c t i n g r e s u l t s . . I t i s t y p i c a l of the approach of continuity theorists that Spence's c r i t i c i s m s of Krechevsky's "hypotheses" were framed i n the form of questions which the experimenter must ask. Spence has e x p l i c i t l y 10 stated that his concern i s not with description of behaviour but with the axioms necessary to predict behaviour. He consequently asks, f i r s t : What, for the animal, constitutes f a i l u r e of a hypothesis lead-ing to i t s abandonment? second : How i s the change made when an an-imal adopts a new hypothesis i n preference to the one i n use? t h i r d : What determines the order of preference of hypotheses? Unfortunately these questions have never been d i r e c t l y answered i n the opposing camp p a r t l y because an answer, at the present stage of investigation cannot be given a u t h o r i t a t i v e l y . Krechevsky's point of view was c l a r i f i e d by him i n an a r t i c l e (22) replying to Spence. The po s i t i o n taken was that the two approach-es to the problem of systematic solutions were not contradictory, the l a t t e r writer simply providing a theory of the mechanism underlying the behaviour i s o l a t e d and described by the f o r m e r I t i s of methodolog-i c a l i n t e r e s t here that Krechevsky regarded his approach as a molar description neither more nor less s c i e n t i f i c than the molecular view-point of Spence. This d i s t i n c t i o n i n approaches has persisted, and constitutes a pregnant source of misunderstanding i n comparing the two positions. The c r u c i a l issue remaining was whether the animal, i n respond-ing, learns the correct solution gradually, throughout the presolution period, or rap i d l y , with the development of the appropriate systematic This was a genial oversimplification on Krechevsky's part. He continued to defend the purposive nature of hypotheses as he had previously defined i t . 11 response. Krechevsky's p o s i t i o n was concisely formulated i n a subsequent a r t i c l e (24) i n these terms, that with each correct or incorrect response the animal learns something about the "significance" of the cue, but nothing about i t s Tightness or wrongness, u n t i l i t has adopted the correct hypothesis. The same author's stand on the effect of reward reversal (22) was that i f the animal were to respond on the basis of an inappro-priate hypothesis during the presolution period, reversal would have no effect upon the rate of learning. However, i f the animal should respond on the basis of two or more c o n f l i c t i n g hypotheses, one of them correct, reversal would i n t e r f e r e with the learning. The d i s t i n c t i o n , t h e o r e t i c a l -l y , i s that according to Spence, reversal must necessarily i n t e r f e r e with learning, while to Krechevsky reversal may or may not have t h i s effect. A further t h e o r e t i c a l issue which appeared at t h i s point con-cerned the d e f i n i t i o n of the stimulus. McCulloch (34) as w e l l as Spence (41) made the point that the animal w i l l not acquire habit strength to-ward a stimulus of which i t i s not aware. In the words of the former author, learning w i l l occur "only i f the relevant s t i m u l i so affect the sensorium that the associations formed are s i m i l a r to those upon which the f i n a l habit i s based". I t w i l l be seen that t h i s statment represents a r e f i n i n g of the continuity position and tends to reduce the distance separating the theories. A p a r a l l e l d i s t i n c t i o n concerns the d e f i n i t i o n of awareness, which to the non-continuity position i s a psychological orientation involving active selection, and to the opposing view i s a physical orientation which i s a function of the animal's response tend-encies and re s u l t s i n a l i m i t e d set of s t i m u l i impinging on the sensorium. 12 This d i s t i n c t i o n was made by Haire (9) who also put forward the i n t e r e s t -i n g suggestion that the c r i t i c a l point at which the animal changes i t s hypothesis may be preceded by a period of reorganisation and hence can-not be determined from the animal's behaviour. That i s , that the operat-i o n a l d e f i n i t i o n of hypotheses i n terms of the 3 sigma chance zone l i m i t a c t u a l l y refers to the application of the hypothesis which may be preced-ed by the hypothesis i t s e l f , the l a b i l e period being during the formation of the hypothesis and not determinable from an examination of response tendencies. While the anthropocentrism of t h i s view i s probably not acceptable to either group, i t indicates the d i f f i c u l t y of precisely formulating the non-continuity posi t i o n . This point also serves to introduce another th e o r e t i c a l concept presented by Spence (43)> that of "preparatory responses", or as they were l a t e r c a l l e d (45), "receptor exposure adjustments". These are the series of responses which the animal makes on the basis of the excitatory p o t e n t i a l of various elements i n the stimulus configuration, and which produce proprioceptive s t i m u l i which are cued into the learning s i t u a t i o n . This concept w i l l be examined more f u l l y presently. The th e o r e t i c a l issues introduced thus f a r , v i z . , "random" ver-sus "systematic" responses, sudden discontinuous versus gradual continu-ous learning, "psychological" versus "physical" orientation, stimulus d i f f e r e n t i a t i o n a function of selective attention as opposed to response engendered exposure of the sensorium, and l a b i l e versus stimulus bound behaviour i n the presolution period, represent what might be thought of 13 as the " c l a s s i c a l " period"'* i n the continuity controversy. I t i s con-venient at t h i s point to summarise the major t h e o r e t i c a l assumptions which underly these issues before proceeding to an examination of the experimental evidence f o r each position. They are as follows (the l e t t e r s N and C are self-explanatory) : (1) C - the stimulus elements to which the animal responds are those which have the highest excitatory potent-i a l at any point i n the learning process. N - the stimulus elements to which the animal responds are those which are relevant to i t s cognitive organisation of the s i t u a t i o n at any point i n the learning process. (2) C - a l l stimulus elements impinging on the animals sensorium at the time of a response w i l l acquire an increment or a decrement i n excitatory potential as the response i s reinforced or not reinforced. N - only those stimulus elements which are relevant to the animal's hypotheses w i l l form the basis of the animal's learning. These are the two basic assumptions, though possibly not the only ones, employed by each p o s i t i o n . From them certain c o r o l l a r i e s may be drawn : ^ This d i v i s i o n i s a r b i t r a r y but i s f e l t to be convenient to the presentation. The d i s t i n c t i o n i s between the period i n which basic issues were introduced and that i n which these issues were reapplied and refined. 14 (1) C - the animal's performance i n a new si t u a t i o n w i l l be a function of the S-R connections i t has ac-quired i n the past. N - the animal's performance i n a new situ a t i o n w i l l be i n part a function of i t s perceptual organis-ation of the s i t u a t i o n as w e l l as of i t s past experience. (2) C - performance at any given time w i l l be t h e o r e t i c a l -l y predictable on the basis of the animal's past experience. N - performance at any given time w i l l not be predict-able since the perceptual organisation of the animal can only be inferred after the response. In addition, the t h e o r e t i c a l issues mentioned i n the preceding discussion may either be derived from these assumptions, or constitute d e f i n i t i o n s necessary to them. Certain features of the controversy become clear i n the l i g h t of these assumptions. I t w i l l be noticed that the non-continuity p o s i t i o n cannot be stated as e x p l i c i t l y as the continu-i t y p o s i t i o n . I t w i l l also be noticed that the d e f i n i t i o n of terms i s an important course of the d i s t i n c t i o n between the two theories. While i t appears so s u p e r f i c i a l l y , i t would probably be unwise to conclude that the number of assumptions i n turn underlying these de f i n i t i o n s (e.g., "reinforcement", "cognition") i s any greater for the non-continuity than 15 f o r the continuity theory. 1 Experimental Issues Having d i s c u r s i v e l y treated the theo r e t i c a l background of the continuity controversy, i t i s appropriate to turn to the experimental evidence which has been adduced to support each of the views outlined. While there has not been a large number of experiments directed specif-i c a l l y t o the controversy, the number has been s u f f i c i e n t l y great to preclude a detailed treatment here of each experiment. Rather than present a s u p e r f i c i a l treatment of every experiment, therefore, i t i s proposed to treat i n d e t a i l those representative experiments which have contributed to the controversy, mentioning others i n passing only i f they seem to add to the development of the discussion. There have been four h i s t o r i c a l approaches to the controversy : (a) observation of pre-soluti o n behaviour (15) (16) (17) (26) (27) (28); (b) the reversed pre-t r a i n i n g experiments (5) (24) (33) (37) (41) (42) (44)J (c) experiments with altered set during learning ( l ) (7) (30) (31); and (d) application of c o r r e l a t i o n techniques to discover the relationship between frequency of reinforcement i n the pre-reversal period and number of errors i n the post-reversal period ( l ) (30) (41) (42). The references do not exhaust the experimental l i t e r a t u r e . The f i r s t type of experiment, as has been noted, d i d not prove f r u i t f u l and was abandoned early i n the controversy. The other three types w i l l be treated i n the order l i s t e d . x Properly, the terms "continuity" and "non-continuity" re f e r only to assumption number (2). 16 The reversed pre-training experiment was f i r s t performed i n the i n t e r e s t of the continuity controversy by McCulloch and Pratt (33). I t was undertaken to te s t the proposition that " r e p e t i t i v e t r a i n i n g produces a cumulative effect i r r e s p e c t i v e of the 'hypothesis' being tested". Two further questions were asked by the experimenters : I f change i s cumulative, i s i t the same throughout? Is there an ir r e l e v a n t " f a m i l i a r i s a t i o n " period? The experiment employed a weight discrimin-ation problem with the following procedure. Five groups of rats (N = 24 i 1) received three successive days t r a i n i n g , 6, 8, and 10 t r i a l s per day, with equally weighted strings (50 gms) to secure food which was placed 110 cms. from the' t r a i n i n g cage. Reward relations were randomly allocated and the animals were allowed to eat for 5 seconds i f successful. T r i a l s were carried out at the same time each day. This preliminary t r a i n -ing was undertaken to f a m i l i a r i s e the animals with the apparatus and pro-cedure. The f i v e groups were then treated as follows : Group 1 - 2 1 days minimum on the f i n a l problem (75 gms. po s i t i v e , 25 gms. negative) to a c r i t e r i o n of two successive days (24 t r i a l s ) without error. An error consisted i n drawing the incorrect weight a distance of 90 cms. Group I I - 28 t r i a l s i n the reverse of the f i n a l problem followed by the i d e n t i c a l procedure f o r Group I. Group I I I - Trained i n the reversed problem t i l l they "seemed to begin to discriminate", (2 days with not more 17 than 6 errors). Errors for t h i s c r i t e r i o n i n c l u d -ed "negative errors", i . e . , drawing the correct weight not more than 15 cms., and "negative h a l f -errors!', i . e . , drawing the correct t r a y not more than 90 cms. Training i d e n t i c a l to Group I follow-ed. Group IV - Overtrained on the reversed problem f o r 249 t r i a l s beyond the mastery mean of 99 t r i a l s , then treated as Group I . Group V - Trained on equal weights to the median for Group I I I pre-reversal, then treated as Group I . The results of t h i s experiment were that each of the experiment-a l groups, with the exception of Group V, produced s i g n i f i c a n t l y higher error scores than d i d the Control Group, i n d i c a t i n g that i n each case reversal of reward relations had had an adverse effect upon learning. In the case of Group I I , r e s u l t s for which indicated that e a r l y t r a i n i n g d i d not represent a f a m i l i a r i s a t i o n period, the authors suggest that the animals may already have been f a m i l i a r i s e d i n the preliminary t r a i n i n g . Results for Group V were inconclusive. The r a t i o of pr e - s h i f t to post-s h i f t errors was also analysed and increased s i g n i f i c a n t l y f o r post-shift errors. A point of interest i s the difference between Group IV pre-s h i f t errors and the t o t a l errors f o r the Control Group, which showed a s i g n i f i c a n t l y better performance i n mastery of the reversed problem before the s h i f t . This was attri b u t e d to the " p r i n c i p l e of le a s t e f f o r t " . 18 The authors concluded that learning i s cumulative from the begin-ning of t r a i n i n g , roughly proportional to errors, and i s i n progress before i t i s evidenced. They also concluded that hypotheses were an i n s i g n i f -i c ant factor and that the animals were not l a b i l e or docile at the c r i t i c -a l point as experimental 1y defined. This experiment tiras subjected to a number of c r i t i c i s m s which throw some l i g h t both on the non-continuity theory and on the experiment-a l issues. Krechevsky (24) made the suggestion that the pre-solution period had been i n c o r r e c t l y defined and should have been shorter. He also put forward the more cogent c r i t i c i s m that the nature of the problem had forced the animals to attend to the relevant s t i m u l i from the begin-ning. I t must be remembered that Krechevsky had never denied a possib-i l i t y f o r the animal to respond on the basis of c o n f l i c t i n g hypotheses and hence to " p i l e up his score for either kind" (16). He also pointed out that "the t y p i c a l discrimination curve i s obtained only where the discrimination i s a more or l e s s d i f f i c u l t one". I t was also noted that the animals were shifted to a harder problem, thus i n effect the animals started with the "correct" hypotheses from the beginning. Haire (8) suggested the p o s s i b i l i t y that the weight discrimination problem favoured the formation of multiple hypotheses, which would bring the error score near the chance l e v e l , and hence that the experimenters' con-clusion that error scores of t h e i r i n d i v i d u a l animals d i d not indicate (with one exception) the simultaneous action of two hypotheses was un-founded. While there i s some sophistry i n these c r i t i c i s m s , there i s also s u f f i c i e n t weight that the McCulloch and Pratt experiment cannot be 19 regarded as s a t i s f a c t o r y evidence. One of the experimenters g a l l a n t l y admitted, i n a lower case footnote to a subsequent a r t i c l e , that the difference i n d i f f i c u l t y of the two discriminations tended to weaken t h e i r r e s u l t s . I t was also agreed that the weight discrimination had forced the animals to"make the proper muscular a d j u s t m e n t s f r o m the beginning and thus t o receive d i f f e r e n t i a l stimulation. An experiment which may be compared with that of McCulloch and Pratt, and was i n fact designed to answer i t , i s that of Krechevsky (24). The Lashley jumping apparatus was used to set up a discrimination between two stimulus cards consisting of horizontal rows of black dashes opposed to v e r t i c a l rows of the same si z e and number. This f u l f i l l e d the re-quirement of a d i f f i c u l t discrimination, which i s c r u c i a l to the outcome of the experiment. Three groups of r a t s , ranging from N 14 to N 17, were f a m i l i a r i s e d i n the apparatus by being jumped through black cards. The groups were then treated as follows : Group I - Trained on the v e r t i c a l rows, 10 t r i a l s per day to a c r i t e r i o n of 18 of 20 errorless t r i a l s on two successive days. The positions were random-ised, and each pair remained standing t i l l the animal succeeded (correction method). Group I I - Trained for 20 t r i a l s (2 days) i n the reverse of x This polemical tendency of each of the protagonists to i n -voke the jargon peculiar to h i s bias i s an in t e r e s t i n g comment on the origins of misunderstanding! 20 the above discrimination, and then treated as Group I . Group I I I - Trained for 40 t r i a l s on the reversed problem, followed by treatment for Group I. In t r e a t i n g the r e s u l t s two methods were used. The t o t a l errors 1 were scored for the Control Group from the beginning of t r a i n i n g , and each experimental group was scored on errors after the reversal; then the same procedure was used with the corresponding number of pre-shift t r i a l s being deducted from the Control Group. Error scores were also divided into i n i t i a l and r e p e t i t i v e errors on the basis of the correction technique. Results f o r Group I I supported the non-continuity prediction that reversal should s l i g h t l y f a c i l i t a t e learning since some of the errors of the non-reversed group are wasted. Differences were s i g n i f i c a n t for both t o t a l and i n i t i a l errors i n the entire t r a i n i n g series, and f o r post-s h i f t scores. Group I I I , on the other hand, produced s i g n i f i c a n t l y high-er error scores, thus f a i l i n g to sustain the expectation of non-continuity theory. This r e s u l t was explained by Krechevsky as an i n d i c a t i o n that f o r t y t r i a l s was too long for the pre-solution period. This reasoning has been c r i t i c i s e d (37) but seems adequate on the basis of Krechevsky's e a r l i e r statements. From these r e s u l t s the experimenter concluded that learning i s not cumulative, that the pre-solution period i s i r r e l e v a n t to the actual learning of the problem, and that the residual effect of reward i s not the same i n the pre-solution period as i n the period after I 21 adoption of the appropriate hypothesis. Several c r i t i c i s m s of t h i s experiment also have been put f o r -ward. One of these has been mentioned e a r l i e r , that the experimenter must be certain that the relevant cues are a c t u a l l y impinging on the animal's sensorium (34)* At the same time i t was pointed out that the decrease i n r e p e t i t i v e errors by the correction method favoured the ex-perimental groups since such errors tend to be eliminated i n the f i r s t two days. Spence elaborated the f i r s t of these c r i t i c i s m s by pointing out that the rats tend to jump to the lower part of the card i n the Lashley apparatus, and also that they tend to jump to the brightest stimulus element, and consequently may not have been f i x a t i n g the appro-pria t e cues (43) i n the early phase of the experiments. This argument i n part rests on establishing the area of the rat's binocular v i s u a l f i e l d . Spence has i n mind, with the term " f i x a t i o n " , the "area corres-ponding to the fovea c e n t r a l i s i n man" with decreasing s e n s i t i v i t y from t h i s point outward to the periphery. Lashley maintained that the expos-ure of the stimulus cards was adequate since the r a t ' s binocular v i s i o n covers an angle of from 50 to 100 degrees. Spence also objected to Krechevsky's explanation of the results f o r Group I I I on the grounds that i t could not be proven that the rats were responding on the basis of the correct hypotheses i n the l a t e r pre-reversal t r i a l s . Other experiments were run on the reversal problem, one by Spence with chimpanzees (42) which was unacceptable to the non-continuity theorists because the animals were forced to attend to the correct cues i n the preliminary t r a i n i n g . One further example of t h i s type of 22 experiment may be c i t e d , because i t attempted to correct t h i s deficiency. Spence, i n 1945, performed an experiment with rats (44) on a black and white a l l e y discrimination designed as follows. Two groups (N = 20) were given t h i r t y rewarded runs to t h e i r own preferred side i n neutral grey a l l e y s . The control group was then given twenty t r i a l s i n which black and white were each 50$ rewarded, the position response being r e -tained by the animals under these conditions. The experimental group was given the reverse of the f i n a l problem for twenty t r i a l s . Both groups were then given a s u f f i c i e n t number of t r i a l s i n the grey alleys to eliminate the position preference. They were then run to mastery i n the f i n a l problem. There was a s i g n i f i c a n t difference i n the perform-ance of the two groups i n the f i n a l problem (70-95 t r i a l s ) which favoured the continuity theory. The design of t h i s experiment was intended to ensure that the animals of the experimental group were responding on the basis of an i n -appropriate "hypothesis" i n the pre-reversal period. This procedure i s open to c r i t i c i s m , however, on the grounds that the experimental group had been trained to two hypotheses each of vihich was successful, while the control group had been trained to one only. Thus i n the f i n a l problem the experimental group i s equipped with two c o n f l i c t i n g hypotheses, which as noted previously would lead t o retarded learning under the as-sumptions of the non-continuity t h e o r y . S p e n c e ' s assumption that because the p osition response had been eliminated after the reversal t r a i n i n g i t This c r i t i c i s m assumes added weight when Harlow's data. (10) are considered. 23 was no longer operant i s based on continuity assumptions, and takes no account of the l a b i l e aspect of behaviour postulated by Krechevsky. A d i f f e r e n t type of experimental t e s t was suggested and per-formed by Lashley (30) involving altered set during learning. Four rats were trained to discriminate between a large (8 cm.) and a small (5 cm.) white c i r c l e i n the jumping stand to a c r i t e r i o n of twenty errorless t r i a l s . They were then presented with two triangles of these dimensions i n which they demonstrated the size preference established. They were trained next to the two triang l e s for 200 t r i a l s , r e i n f o r c i n g the established preference. A c i r c l e and t r i a n g l e of equal intermediate s i z e were then presented and the animals were forced to jump, responses being at a chance l e v e l . Training to the large t r i a n g l e and small c i r -c l e was continued, a f t e r which the animals were presented with a large c i r c l e and small t r i a n g l e . The response was to the large c i r c l e , on the basis of s i z e , and i n contradiction of overtraining to form. This was one of a series of experiments the re s u l t s of which were not s i g n i f -icant but which tended i n the same d i r e c t i o n . ^ The rationale of t h i s experiment i s -that the animals are t r a i n -ed to two stimulus dimensions each of which i s presumably being r e i n f o r c -ed. I f t h i s assumption i s granted the change from c i r c l e to tria n g l e should r e s u l t i n a chance l e v e l of response on the basis of the continu-i t y hypothesis. As noted, the animals responded throughout on the basis of s i z e preference. However, i t should be noted that overtraining to a x The discussion of the v a l i d i t y of t h i s type of evidence i s not f e l t t o belong wit h i n the scope of t h i s section. 24 given form would not necessarily be transferred to a s i m i l a r form of d i f -f e r i n g dimensions, under the assumptions of continuity theory, which emphasise the s p e c i f i c i t y of each stimulus component. This experiment was re-run by Blum and Blum ( l ) with modificat-ions based on t h e i r c r i t i c i s m of the o r i g i n a l . B r i e f l y , these were based on the summation of i n h i b i t i o n a r i s i n g out of the proximity of the two sets of s t i m u l i on the generalisation continuum, which would slow the d i f f e r e n t i a l reaction. They substituted a small inverted t r i a n g l e f o r the small c i r c l e , and ran the experiment omitting the f i n a l t e s t . Five rats learned the preliminary discrimination i n a comparable number of t r i a l s to Lashley's r a t s . When they were tested-on an inverted and an upright t r i a n g l e of equal s i z e , the prediction being that they would jump to the rewarded figure, two of the rats f a i l e d to make the d i s -crimination, were retrained, and succeeded. I t seems remarkable that on t h i s evidence the authors concluded that the continuity position i s upheld, f o r while the resu l t s contradict those of Iashley, the f a i l u r e of the two animals to make the discrimination i n the c r u c i a l test can equally w e l l be explained on the basis of t h e i r having d i f f e r i n g "hypo-theses" . Space does not permit the f u l l e r discussion of t h i s type of experiment, of which there have been several. B r i e f mention might be made of an alternative design i n which the animals are divided into two groups each of which i s trained to a single stimulus card. Both groups are then presented with the two stimulus cards, the continuity predict-ion being that the group which has been reinforced on the negative card 25 of the f i n a l pair w i l l perform more poorly than the group trained to the po s i t i v e card. Lashley and Wade performed t h i s experiment i n the jump-ing stand with results contrary to the continuity expectations (31) • The experiment was repeated by Grice (7) using a discrimination box and a larger number of subjects with the opposite r e s u l t . However there seems to be some doubt as to the v a l i d i t y of t h i s experiment. The tech-nique i s to present the single stimulus opposed to a black card. I t i s assumed that the animal i s responding to the stimulus card only. How-ever, i t i s possible that some of the animals respond on the basis of a "figure/non-figure" or a brightness hypothesis. Thus when the animal comes to the s i t u a t i o n i t has had experience with two c o n f l i c t i n g hypo-theses, and may be expected to respond according to the expectations of either theory on the basis of non-continuity assumptions. While the transposition experiments seem promising, the contradictory results thus fa r obtained (7), combined with the f a i l u r e of the experimenters to meet the assumptions of both theories, make them as yet an unsatisfactory instrument. The material above serves a useful purpose, however, i n i l l u s t r a t i n g the extreme d i f f i c u l t y of formulating the non-continuity theory with any degree of precision. One further general type of evidence remains to be considered before turning to the recent work. Spence (42) suggested that one con-sequence of the continuity assumption would be to produce a correlation between the number of errors made p r i o r to the s h i f t of reward r e l a t i o n s , and the error scores a f t e r the s h i f t . He applied the method to his data and obtained a high rank order c o r r e l a t i o n . Lashley (30) reviewing the 26 controversy i n 1942, pointed out that a correlation could exist even with a high chance factor. He suggested that a more c r u c i a l test would be t o remove systematic errors from the data, which, i f the continuity assumpt-ions were correct, would r e s u l t i n a lowering of the correlation. Rework-ing Spence's data, he found the opposite to be true. Blum and Blum ( l ) repeated his work, however, using a product-moment technique and obtained the opposite r e s u l t . The conclusion of these authors i s that the cor-r e l a t i o n technique i s not s u f f i c i e n t l y sensitive at present to j u s t i f y i t s use i n t h i s way. Recent Trends I t w i l l be seen that during what we have chosen to regard as the " c l a s s i c a l " period of the controversy, two tendencies have been mani-fested. On the one hand there was a progressive c l a r i f i c a t i o n and r e f i n e -ment of the t h e o r e t i c a l position of each group, while on the other there was a successive introduction of new experimental problems and techniques. Before reviewing the recent experiments, i t w i l l be o f interest to sum-marise b r i e f l y some of the important experimental issues, since the value of an experiment directed toward the problem must be judged by the extent to which i t meets and overcomes the inadequacies of past attempts. ( l ) Probably the most important issue l i e s i n the appropriate d e f i n i t i o n of the pre-solution period. For the non-continuity th e o r i s t , the pre-solution period ends when the animal adopts the correct hypothesis. I t has been seen that the c r i t e r i o n determining t h i s point, while i t must 27 be behaviourally defined i n a broad sense, cannot v a l i d l y be assumed to be the point at which the correct response begins to be evidenced. (2) The d i f f i c u l t y of the discrimination i s c r u c i a l f o r the experimental r e s u l t s . _Only a problem of s u f f i c i e n t d i f f i c u l t y that the animal i s forced to test successively at l e a s t two "hypotheses" i s admis-sable as evidence for either theory. Of importance i n t h i s connection i s the experimental p o s s i b i l i t y that the animal i s responding simultan-eously to two hypotheses, with apparent chance scores. (3) From the standpoint of continuity theory the question of the a v a i l a b i l i t y of the relevant cues i s perhaps a restatement of the " d i f f i c u l t y " of the problem. However, here the terms of reference are the exposure of the sensorium i n the apparatus, and p a r t i c u l a r l y the actual v i s u a l f i x a t i o n at the moment of response. (4) No less important are the movements which the animal makes when f i r s t i n the apparatus, both those which may be considered receptor exposure adjustments, and those which are purely an outcome of the p a r t i c u l a r apparatus or mode of entry. (5) F i n a l l y , the issue of correction versus non-correction methods of t r a i n i n g has been demonstrated to have some influence on the r e s u l t s , since the correction method results i n the early elimination of pos i t i o n responses, and also r e s u l t s , i n the terms of the continuity t h e o r i s t s , i n the summation of i n h i b i t i o n which may generalize to each of the s t i m u l i . 28 An experiment which was directed at the f i r s t of these issues, the d e f i n i t i o n of the pre-solution period, has been carried out by Prentice (36) with human subjects. I t was based on the assumption that the verbal reports of the subjects themselves w i l l provide the most ade-quate d e f i n i t i o n of the state of solution. The second experimental issue was also attacked i n that the problem presented was extremely d i f f i c u l t . This experiment i s noteworthy i n that the stimulus relations t o be learn-ed were such as would be expected t o c a l l f o r t h a considerable number of possible hypotheses. Subjects were given two keys, one marked with a c i r c l e , the other with a square. They were instructed to press either key as each pair of s t i m u l i were presented, a correct response r e s u l t i n g i n a l i g h t , incorrect i n a buzzer. Stimulus cards consisted of eight pairs of cards presented i n random order, such that the choices to be made were between c i r c l e or square, l i g h t or dark background, large or small f i g u r e , r i g h t or l e f t position i n t h e i r various possible combin-ations » The correct response was to press the key marked with a c i r c l e whenever a figure with a dark background appeared on the r i g h t . Sub-jects were asked to verbalize t h e i r responses. Two groups (N = 20) were used, the control group being trained to a c r i t e r i o n of twelve er-rorless t r i a l s . The experimental group was given twenty t r i a l s with the reverse of the problem, then trained to the same c r i t e r i o n as the control. They were not t o l d that the problem had been changed. Sub-jects who f a i l e d t o make the discrimination after 100 t r i a l s , and those who succeeded before twenty t r i a l s were treated separately i n the r e s u l t s . Ignoring subjects who f a i l e d , the control group solved the 29 discrimination i n twenty t r i a l s less than the reversal group. Thus, i f the twenty p r e - s h i f t t r i a l s of the control group are ignored (cf. Krechevsky (24) ), each group was approximately equal. The authors argue that since f o r each group subjects were aware of only one problem, the t o t a l r e s u l t s should be compared. This i l l u s t r a t e s the d i f f i c u l t i e s inherent i n the non-continuity theory. Provided i t s assumptions were correct, the r e j e c t -ion of a hypothesis would s t i l l have an effect on post-reversal learning, without granting any of the assumptions of the continuity theory. The author interprets the continuity theory as predicting a difference not of twenty t r i a l s but of f o r t y , i . e . twenty t r i a l s to unlearn the pre-s h i f t responses and twenty more t r i a l s to learn the post-sh i f t problem. While oversimplified, t h i s suggestion i s undoubtedly cogent. Verbal reports were not as h e l p f u l as might have been supposed i n determining the state of solution. A further r e s u l t was that subjects who f a i l e d to make the discrimination showed no s i g n i f i c a n t differences between the groups. The author concludes that there was some continuous reinforce-ment, but that i t was not the major determinant, and suggests that mechanical stimulus-response learning was probably most effec t i v e i n the early t r i a l s . The factors i n t h i s experiment are obviously extremely complex, and i t might be questioned whether the s i t u a t i o n i s even minimally comparable to that i n past experiments. However, this type of study w i l l apparently introduce new issues and might prove of value. Cne conclusion that may be drawn from these r e s u l t s i s that neither the continuity nor the non-continuity theory i s adequately stated. An experiment with rats which was aimed at the control of 30 attention presents more clear-cut r e s u l t s . Ehrenfreund (5) , i n what i s probably the best controlled and c e r t a i n l y the most adequately reported experiment on the controversy to date, duplicated Krechevsky's experiment (24), taking account of the c r i t i c i s m s which had been put forward by Spence (23). I t w i l l be r e c a l l e d that these centered on the question of the rats a c t u a l l y receiving the s t i m u l i on t h e i r sensoria during the pre-solution t r i a l s . The experiment was conducted i n the Lashley jump-ing stand modified so that a two-pronged platform brought the animals d i r e c t l y i n front of the stimulus cards. The correction technique was used to a l i m i t of four r e p e t i t i v e errors. After being f a m i l i a r i z e d with the apparatus, both groups (N = 15) were given f i v e t r i a l s to the r i g h t i n response to a white square on a black background, i n order to establish a p o s i t i o n habit. The control group were then given equal reward and f r u s t r a t i o n on each card, while the experimental group was trained f o r f o r t y t r i a l s to the card which appeared f i r s t on the r i g h t . The stimulus cards presented a choice between an upright and an inverted t r i a n g l e , each placed at the top of the stimulus card. F i n a l l y , f i v e t r i a l s p o sition reversal were given each group, and each was trained on the f i n a l discrimination to a c r i t e r i o n of 9C$ errorless t r i a l s . The r e s u l t s of t h i s procedure were that the two groups d i f f e r -ed only by chance expectations, as Krechevsky had found. The experiment was then repeated i n a l l d e t a i l s except that the stimulus figures were placed at the center of the card, and the platform was adjusted so that the r a t was obliged to jump d i r e c t l y to the figure. Results gave high-l y s i g n i f i c a n t differences i n number of t r i a l s , number of i n i t i a l errors 31 and number of r e p e t i t i v e errors i n favour of the non-reversed group. Further, t h i s group did s i g n i f i c a n t l y better than did the control group i i n the f i r s t experiment. The author's conclusion i s that where an easy discrimination i s made, the results are clear-cut f o r the continuity t h e o r i s t s , who have never denied that conditions could be arranged so that no discrimination would be made, and consequently no habit strenth accumulated. This experiment w i l l be discussed further i n connection with the design of the present investigation. Yet another group of experiments i s of i n t e r e s t , those of Harlow (10), who demonstrated the capacity of chimpanzees and children to acquire learning sets. His findings are pertinent i n in d i c a t i n g that something l i k e a "hypothesis" may be learned with a high degree of eff i c i e n c y , such that the animals are capable of changing t h e i r responses on the second reversed t r i a l . " 1 " In a subsequent paper (11) the author suggested that the controversy i s a r t i f i c i a l i f past'experience i s taken i n t o account. He also states that both the in d i v i d u a l responses, and the learning sets, are gradually acquired, apparently on the basis of continuous reinforcement. This statement must be evaluated, however, with reference to the fact reported e a r l i e r , that a l l the Discriminations used were those which "could r e a d i l y and probably immediately be per-ceived by the subjects" (10). These and s i m i l a r studies on primates introduce an aspect of This phenomenom i s clos e l y analogous to the "conditional reaction" described by Lashley i n 1938 (29), and i s i n fact an outgrowth of the e a r l i e r study. 32 the controversy which has received l i t t l e attention i n t h i s f i e l d of learning theory, v i z . , the phyletic implications of behavioural descript-i o n . While the issues remain i n doubt for experiments with r a t s , the recent work of Harlow, Evart and Nissen, and others of the Orange Park groups suggests that the controversy may be meaningless where primate behaviour i s concerned. In p a r t i c u l a r the routine use of the "single cue t e s t " of'abstraction", i n which the animals are trained to a d i s -crimination of multiple stimulus dimensions and are then tested on each dimension separately, y i e l d s a "normal" performance i n which each dimension i s correctly responded to (cf. the "altered set" experiments discussed e a r l i e r ) . The fact that t h i s behaviour i s r e l a t i v e l y sens-i t i v e to c o r t i c a l ablation implies that the phylum stage may be a major determinant, and suggests that the present controversy needs to be placed i n an appropriate perspective. (Indeed, the c o n f l i c t between cognitive and S-R theories of learning, which the controversy represents, may hinge l a r g e l y on the developing d i s t i n c t i o n between "abstract" and "concrete" behaviour, and on the prediction of the conditions under which each occurs i n various species.) One further type of experiment, although not directed primar-i l y at the controversy, merits attention before turning to a review of the very recent work. These are the attempts to apply factor analysis to the learning process. Wherry (47) has applied Thurstone's technique to data from Yoshioko's experiments with pattern discrimination, arranged so that intercorrelations could be drawn for each r a t f o r each ten t r i a l s during the learning series. (This arrangement arises out of the con-33 troversy over the e f f i c a c y of lumped data which does not primarily con-cern us here.) One of his findings was a confirmation of Krechevsky's "hypotheses" for insoluble problems. I t should be remembered however that the factors producing hypothesis formation as a molar phenomenon! i n 3 X 1 insoluble problem can be given adequate d e f i n i t i o n by the continuity theorists (40) • A l a t e r study by Rethlingshafer (3&) using data from Muenzinger, i s o l a t e d three factors by a s i m i l a r technique. One of these, the second i n order of percentage contribution t o variance, was a " r i s i n g and waning factor" which the author i d e n t i f i e s as " v a r i a b i l i t y i n the adoption of hypotheses". While neither space nor the writer's competence permits a detailed discussion of t h i s type of evidence i t i s apparent that the processes involved i n discrimination learning a t t a i n a l e v e l of complexity which i s not adequately met by either the continuity or the non-continuity descriptions of learning. The most recent review of studies i s that by Harlow i n the "Annual Review of Psychology, 1952". These studies w i l l not be discussed i n d e t a i l here, since they contribute nothing e s s e n t i a l l y new i n approach or r e s u l t s . The box score favours the continuity position, with the reservations noted i n the next section. One of these studies, that by Ri t c h i e (39) i s remarkable how-ever c h i e f l y as an i l l u s t r a t i o n of what i s not acceptable i n an experiment-a l approach to the controversy. Rats were trained i n the Lashley apparatus using a pattern discrimination, and reversing the reward relations i n the usual manner. The f i v e part design of Spence was employed, which i s i n i t s e l f objectionable, though perhaps not c r u c i a l l y so. In describing 34 the experiment the authors mention that the experimental animals were more "prone" to posi t i o n hypotheses than were the controls, and that three of the animals had to be discarded because they had already learn-ed the discrimination during the "pre-solution" period! Both of these factors would lead to a prediction of retarded learning on the basis of either theory, i n spite of which the authors put forward t h e i r r e s u l t s as favouring the continuity p o s i t i o n . The tendency here to place under attack a lud i c r o u s l y s i m p l i f i e d version of the opposing theory has been noted previously. Summary Summarising, very b r i e f l y , the h i s t o r i c a l development of the controversy i t w i l l be seen that while the trend of experimental studies has favoured the continuity p o s i t i o n , there has been a s u f f i c i e n t weight of evidence f o r the opposing view that i t cannot be discounted. Further, there has been some difference i n the types of experiment which favour each viewpoint. Thus Blum and Blum ( l ) point out that experiments i n -volving massed t r i a l s , punishment of the incorrect response, and the cor-rection method tend to favour the non-continuity position, while those i n which these conditions do not obtain have tended i n the opposite d i r e c t -io n . Another d i s t i n c t i o n which i s evident i s that experiments involving simple quantitative discriminations, or very simple form discriminations have tended to favour the continuity position, while those involving more d i f f i c u l t discriminations, or perceptual factors, have not. There i s an implication then that each theory may be appropriate to a p a r t i c u l a r 35 type of learning; and there i s the alternative implication that experi-mental factors demonstrating one or the other prediction may have been inadequate. These experimental factors obviously need c l a r i f i c a t i o n . C l a r i f i c a t i o n of the t h e o r e t i c a l issues i s also needed. Blum and Blum ( l ) suggest that for continuity theory the factors of extinction, reactive i n h i b i t i o n , and conditioned i n h i b i t i o n are not s u f f i c i e n t l y c l a r i f i e d to permit of adequate quantification. On the other hand the d e f i n i t i o n of "hypotheses" and p a r t i c u l a r l y the r e l a t i o n between simul-taneous and successive "hypotheses" needs c l a r i f i c a t i o n i n non-continu-i t y theory. I f t h i s theory i s i n any way adequate i t should be possible to perform experiments i n which the number and nature of "hypotheses" can be controlled. In both theories the d e f i n i t i o n s of attention and awareness need further c l a r i f i c a t i o n . I t i s unfortunate that the non-continuity theorists have at no time attempted t r u l y rigorous d e f i n i t i o n of t h e i r concepts l i n k i n g them t o antecedent variables. Spence i n con-sidering t h i s aspect of the controversy holds that the non-continuity theorists have misunderstood the continuity position, which i s however not as yet adequately developed f o r problems of perception. By way of summary also, i t might be mentioned that, while t h i s factor has been minimised i n the presentation, i n the i n t e r e s t of c l a r i t y , there has been a considerable tendency f o r the members of each group to misunderstand or misrepresent t h e i r opponents' case to gain a polemical advantage. More serious i s the extent to which experiments have been performed which v i o l a t e conditions of one or other of the positions, the res u l t s of which are then offered i n support of the writer's bias. 36 Leeper (32) i n a b r i e f but very cogent summary of the issues notes that the controversy has been hampered by loose use of terms, ignoral of ex-periments, use of t a c i t assumptions, and by the tendency to claim support fo r one position by claiming to have disproved the other. He also holds that the controversy i s p a r t l y a pseudo-issue and that both theories are p a r t i a l l y adequate. CHAPTER I I I CLARIFICATION OF THE TWO POSITIONS The Continuity Position Having reviewed, i n i t s s a l i e n t features, the h i s t o r i c a l develop-ment of the controversy, i t i s now possible to undertake a more detailed consideration of the issues involved. A convenient approach to t h i s task i s to consider separately the two positions, i n an attempt to c l a r -i f y t h e i r respective descriptions of the learning process. I t has been seen that a general statement of continuity theory describes discrimination learning as a gradual and continuous summation of increments to the response tendency of the animal toward the associat-ed s t i m u l i with each rewarded occurrence of the response. I t has also been seen that t h i s general statement must be q u a l i f i e d by a consider-ation of the factor of attention. A further q u a l i f y i n g factor i s the effect of stimulus generalization. Blum and Blum ( l ) have presented t h i s aspect of continuity theory i n explanation of the experimental trends noted above, v i z . , effect of massed t r i a l s , punishment, and the correct-ion method. Their explanation, based upon stimulus generalization and int e r a c t i o n , i s a model of sophistication, and demonstrates n i c e l y the d i f f i c u l t y of t e s t i n g the two theories. I t i s suggested that the actual afferent stimulus compound, to which the appropriate response w i l l eventual-l y be cued, i s composed of three temporal un i t s : the positive stimulus 38 card, the s i t u a t i o n a l cues, including the presence of the other stimulus card and of movement cues, and the reward stimulus. S i m i l a r l y the af-ferent stimulus compound which w i l l eventually e l i c i t an avoidant res-ponse consists of the stimulus of the negative card, the s i t u a t i o n a l cues, and the non-reward stimulus. Obviously the stimulus component represent-i n g s i t u a t i o n a l cues w i l l contribute the largest element to the afferent compound i n the early phases of learning, and w i l l be i d e n t i c a l for the rewarded and the non-rewarded compounds. Thus during a part of the pre-solution period the gradual accumulation of excitatory potential to the p o s i t i v e card w i l l be masked by the presence of these elements. I f the s i t u a t i o n favours the summation of i n h i b i t i o n through massed t r i a l s , and through punishment of the incorrect response, p a r t i c u l a r l y the repeated punishment involved i n the correction method, the generalization of i n -h i b i t i o n and e x c i t a t i o n each way between the f i r s t two temporal elements of the stimulus compound w i l l make them v i r t u a l l y equivalent, and the p o t e n t i a l of each compound w i l l be determined almost s o l e l y by the t h i r d element, the reward stimulus. But since i n h i b i t o r y potential accumulates more r a p i d l y than excitatory p o t e n t i a l , the reversal of reward relations may a c t u a l l y have the effect of f a c i l i t a t i n g , rather than retarding the learning, p a r t i c u l a r l y i f the two c r u c i a l s t i m u l i l i e close together on the hypothetical generalization continuum i n a d i f f i c u l t discrimination, ( i t w i l l be r e c a l l e d that i n Krechevsky's experiment the reversed group was superior t o the control.) This description rests of course on the additive treatment accorded the afferent compound i n continuity theory, and would be a p r i o r i meaningless i f each stimulus element were considered 39 separately. The effect of i n c i d e n t a l s t i m u l i i n masking the true stimulus generalization gradient has been elaborated and given systematic elegance by H u l l (14) following the suggestions of Blum and Blum. I t i s evident that t h i s type of formulation can be extended with almost i n f i n i t e complexity, and could be made to accommodate the effects of d i s t r a c t i o n , momentary fluctuations i n l e v e l of a c t i v i t y , the progres-sive diminishing of drive during a single experimental session with each successive reward period and so on.-'- Digressing for a moment i t i s in t e r e s t i n g t o speculate on possible applications of these minutiae to other phases of the process. For example, a f t e r the f i r s t few t r i a l s when the two stimulus compounds are s t i l l nearly equal some secondary re-inforcement based on the anticipatory goal reaction would r e s u l t from the animal's merely looking at the correct card, and the successive superposition of the two stimulus patterns on the r e t i n a (VTE) coincid-ent with t h i s state of reinforcement would r e s u l t i n a s l i g h t transfer of excitatory p o t e n t i a l to the negative card, again r e s u l t i n g i n f a c i l -i t a t e d learning of the reversed problem, under the appropriate circum-stances. While i t may be f e l t that t h i s description tends more to sophistry than sophistication, i t i s not inconsistent with the pattern of continuity theory, and serves to i l l u s t r a t e the potential complexity of that pos i t i o n . The obvious danger to molecular systematics i s i n producing an endless array of minutely sophisticated explanations for any experi-mental fact, with a consequent s t i f l i n g of research. In tr i b u t e to the energy of t h i s group of theorists i t should be noted that the danger remains p o t e n t i a l rather than actual. 40 This pattern having been made clear, i t becomes pertinent to attempt a b r i e f description of the animal's behaviour i n the discriminat-i o n learning s i t u a t i o n according to t h i s theory. During the pre-solution period two phases may be distinguished; the f i r s t i n which the animal i s not, properly speaking, responding to the relevant stimulus elements of the s i t u a t i o n , and the second i n which these are responded to, but not i n such a way as to be evidenced by systematic behaviour. Naive behaviour i n the apparatus i s not, of course, regarded as a t r i a l and error process, but rather as the r e s u l t of response ten-dencies already present, either native or acquired, together with accident-a l factors. Thus the animal when f i r s t placed i n the apparatus with a given momentary orientation of the sensoria responds to those stimulus elements which have excitatory value. In the l i m i t e d s i t u a t i o n these responses i n e v i t a b l y bring him to the goal box where he receives food, which constitutes a reduction i n drive-'- and a consequent increment to the excitatory p o t e n t i a l of a l l stimulus elements impinging on the sensoria at the moment of the f i n a l response. This also occurs i n diminishing degree to those elements present to the sensoria p r i o r to the response, depending on t h e i r temporal proximity. Each subsequent t r i a l i n t h i s phase of the learning r e s u l t s i n successive increments to the excitatory p o t e n t i a l of those stimulus elements which were most consistently present at the time of the f i n a l response. As a consequence there i s an i n -creasing tendency on the part of the organism to attend, i n the sense of physical orientation, to these elements. The second phase, and this i s not an abrupt d i s t i n c t i o n , i s on-The d e f i n i t i o n of S-R terminology i s not f e l t to be neces-sary here. 41 going when the animal i s responding to the s i t u a t i o n p r i m a r i l y i n terms of the goal box, i . e . , when the instrumental response i s occurring con-s i s t e n t l y . This does not necessarily imply that the animal i s respond-i n g to the stimulus r e l a t i o n s themselves, since the animal i n running or jumping to the goal box may not be f i x a t i n g the appropriate stimulus at the moment of response, his attention to these elements i n turn occurring gradually i n the manner described above. I f inappropriate systematic responses occur during t h i s period t h e i r occurrence i s ascribed to the accumulation of excitatory p o t e n t i a l to the inappropriate stimulus elements, due to the .fortuitous combination of these with the appropriate ones. The roles of stimulus generalization and i n h i b i t i o n have been described above. During t h i s phase the gradual accumulation of e x c i t -atory p o t e n t i a l to the "correct" stimulus i s masked by the effects of generalization, and by the additional contribution of other stimulus elements which may at any point outweigh the contribution of the appro-pr i a t e elements i n terms of the reaction threshold. This phase ends when a systematic tendency to respond t o the appropriate cues i s evidenc-ed by whatever s t a t i s t i c a l c r i t e r i o n i s selected. The Mon-Continuity Position The non-continuity position suffers by comparison with the r e l a t i v e l y precise formulation of continuity theory, i n that i t does not admit of so detailed an exposition. I t i s concerned with a broader description of the process, though with the underlying implication that the minutiae of determination are not i d e n t i c a l with those of the oppos-42 i n g view. I t has been seen that the fundamental issue i s that of d i s -continuous acqu i s i t i o n of the response. The o r i g i n a l formulation of Lashley regarding the " a l l or nothing" basis of learning has received so l i t t l e support from, and has been contradicted so frequently i n , experi-mental studies, that i t cannot be regarded as an adequate basis for t h i s position. Consequently, nearly the whole burden of the non-continuity po s i t i o n devolves upon the proposition that only those aspects of the stimulus complex which are relevant to the animal's "attempted solutions" are effective i n determining i t s behaviour. The implication i s that the animal selects and organises various discrete aspects of the s i t u a t i o n and responds to these. The term "attempted solution" demands c l a r i f -i c a t i o n which may be referred to the notion of selection, which implies organization, and to the function of reward. Learning i s regarded by both positions as p r i m a r i l y adaptive behaviour, i n which reward or s a t i s f a c t i o n i s the consequence of the learned response, and sustains i t . The "attempted solutions" represent modes of responding which are pur-posive i n the sense that they function as a means of securing s a t i s f a c t -ion or reward. I t seems to be a necessary assumption of t h i s type of theory that the organism i s equipped with an active tendency to secure the maximum s a t i s f a c t i o n of i t s needs, the mechanism of such a tendency being found i n the modes of response which are available to i t . ( I t should be noted that t h i s concept of "active tendency" does not go beyond that of Hull's "drive".) This i s purpose as Huxley defined i t f o r biology, the necessity of continuing the existence of a given organization into the succeeding instant. 43 The r e a l d i s t i n c t i o n then, between the two theories reposes i n the function of reward, which for the non-continuity position has the effect of confirming those responses which are based on an appropriate organization of the si t u a t i o n once that organization has been adopted. That rewards may have a cumulative effect i n the process i s not incon-s i s t e n t with t h i s formulation. (indeed the issues would be more clear i f the non-continuity assertion was simply that reinforcement operates i n terms of response sets rather than i n terms of single responses.) Supplementing t h i s d i s t i n c t i o n i s one which i s equally r e a l but which cannot at present be defined operationally. I t serves, however, to i l l u s t r a t e a difference of conceptualization which i n part gives r i s e to the controversy and which may have operational consequences. This i s the d i s t i n c t i o n between the overview which regards behaviour as "stimulus-bound", the s a t i s f a c t i o n of tissue needs being accomplished i n the course of stimulated a c t i v i t y , and that which regards behaviour as purposive i n the sense that the organism's a c t i v i t y i s directed autonomously toward the s a t i s f a c t i o n of i t s needs, by means which are appropriate to i t s l e v e l of organization. Even t h i s sketchy presentation of non-continuity thinking goes somewhat beyond the formal position adopted e a r l i e r i n the controversy. I t i s regrettably the case that there i s no recent statement of the posi t i o n , and that there has never been a t r u l y adequate systematic statement of i t . However, i t i s possible t o attempt a c l a r i f i c a t i o n of i t s issues consistent with the pattern of the theory, with a view to presenting a meaningful background to the experimental issues. In doing 44 t h i s i t seems f a i r l y evident that the case for the cumulative effect of reward i n a broad sense may be conceded. The question then becomes what i s rewarded or reinforced, and a consistent answer i s that i t i s the cognitive structure on which the response i s based. I t has been seen that experiments which present a simple quantitative discrimination, e.g., brightness, weight, or a very simple form discrimination tend to support the continuity position. These are also, however, experiments i n which the stimulus elements are obtrusive, demand a simple l e v e l of cognitive organization and tend to admit of only two hypotheses, a position hypo-thesis and the "correct" hypothesis. I t would seem to be a meaningful elaboration of non-continuity theory to suggest that hypothesis formation occurs within an hierarchy of l e v e l s of organization, beginning with o l f a c t o r y dominance, as manifested by the s n i f f i n g behaviour characteris-t i c of rats i n a new s i t u a t i o n , and ascending through various levels of sensory dominance to perceptual organization involving the phenomena of pragnanz, and to various systematic combinations of sense modalities. This would postulate a "reluctance" to adopt a higher or more complex l e v e l of organization where a simpler one would achieve s a t i s f a c t i o n , such that, i n general, the animal's cognitive organization of a new s i t u a t i o n would be at a low l e v e l i n the postulated hierarchy, while the demands of a complex s i t u a t i o n would subsequently force the adoption of higher l e v e l s of organization. The p o s s i b i l i t y i s open for i n d i v i d u a l differences to determine the precise order of selection and the l e v e l of usual function as i s analogized i n sorting a c t i v i t i e s with human subjects. This general view i s i m p l i c i t i n Krechevsky's studies on proximity as a 45 factor i n the v i s u a l closure of the r a t (23) (25). One of the outcomes of such a view i s that the response i t s e l f i s regarded as l a b i l e and that a given "hypothesis" or cognitive structure may be r e a l i z e d v i c a r -i o u s l y by a v a r i e t y of behaviours. I t i s not suggested that the fore-going statement i s necessary or complete, nor that an experimental v e r i f i c a t i o n of i t s central issues would v e r i f y the theory as a whole. This i s also true, however, of the ramifications of continuity theory. A b r i e f attempt to describe the behaviour of the non-continuity r a t i n the discrimination apparatus w i l l serve to point out the d i f f e r -ences between the two theories. Again two phases may be distinguished i n the pre-solution period. The f i r s t may be regarded as that i n which the animal i s engaged i n "exploring" the new s i t u a t i o n , i . e . , his behav-iours are a c t i v e l y oriented at a low l e v e l of sensory dominance toward the s a t i s f a c t i o n of his needs. x Haire (9) has suggested that -in t h i s phase hypothesis formation includes attempts at escape and so on. This type of reasoning would seem to contribute l i t t l e to the r e a l issues of the controversy. Rather t h i s phase may be regarded as an active attempt to organize the s i t u a t i o n i n such a way that the animal can function w i t h i n i t t o achieve need s a t i s f a c t i o n . During t h i s a c t i v i t y the goal box acquires significance as a locus of s a t i s f a c t i o n . Again, t h i s phase may be regarded as ended when the animal's a c t i v i t y i s oriented primarily An alternative conceptualisation i s that of Weiss and of Tinbergen by which t h i s r e l a t i v e l y unstructured "appetitive behaviour" i s regarded as the highest l e v e l i n the hierarchy of physiological mechanisms underlying behaviour. 46 toward the goal box. In the second phase the animal responds i n accordance with his cognitive organization of the stimulus r e l a t i o n s . I f the discriminat-ion involves a simple l e v e l of organization the "correct" hypothesis i s r e a d i l y acquired. Under these circumstances, as i n those i n which the animal i s forced to attend to the relevant discriminanda, reversal of the reward relations may very e a s i l y retard learning of the f i n a l l y to be rewarded discrimination. I t w i l l be seen that up to t h i s point there i s no essential operational d i s t i n c t i o n between the two theories. (To the writer's knowledge, no. continuity t h e o r i s t has yet succeeded i n s a t i s f a c t o r i l y predicting the rate of accumulation of excitatory potential i n a given s i t u a t i o n , though t h i s could conceivably be done i f i t were a function of the gradual accumulation of increments rather than of the l a b i l e adoption of a response set.) I f , however, the discrimination involves a complex l e v e l of organization, as i n a d i f f i c u l t pattern d i s -crimination, or one involving two or more sensory modalities, the animal w i l l be obliged to adopt successively a number of hypotheses, and revers-a l w i l l consequently have no effect on the f i n a l learning. This phase ends when the "correct" hypothesis i s more or l e s s consistently adopted, depending upon the s t a t i s t i c a l c r i t e r i o n selected. These two presentations of the c o n f l i c t i n g theories have served to set a background f o r the experimental issues to follow. They also permit of comparision of wider t h e o r e t i c a l issues as, f o r example, the "pe r i p h e r a l i s t " versus the " c e n t r a l i s t " orientations which they em-body, the discussion of .which i s perhaps inappropriate here. One issue, 47 however, which i s of in t e r e s t i n approaching the experimental problem i s again that between the method of axiomatic molecular theory construction and that of molar description. I t w i l l be seen that each approach resu l t s f i n a l l y i n the l i m i t e d factual proposition : reversal of reward relations does/does not i n t e r f e r e with subsequent learning. And while i t becomes apparent that the experimental answer to t h i s question does not f i n a l l y validate either theory, i t i s interesting that the propos-i t i o n i t s e l f must be framed at the molar l e v e l , a fact which invalidates a p r i o r i any ad hoc molecular explanation of the experimental r e s u l t s . CHAPTER IV THE EXPERIMENT C r i t e r i a f o r an Adequate Experiment Holding i n view the material thus f a r presented, attention may now be directed toward ascertaining what might be an adequate experiment-a l test of the opposed theories; that i s , how may the l i m i t e d proposition be affirmed or negated without doing violence to either t h e o r e t i c a l p o s i t i o n . This question may be answered by considering the experimental issues which have been raised. Some of these have been discussed ear-l i e r i n t h e i r h i s t o r i c a l context and need only be reviewed here. I t has already been noted that i n order to s a t i s f y the requirement of non-continuity theory the discrimination must be s u f f i c i e n t l y d i f f i c u l t that the animal i s obliged to adopt successively at l e a s t two "hypotheses". Also noted was the problem of defining the pre-solution period. In the absence of adequate s t a t i s t i c a l c r i t e r i a the most suitable means of doing t h i s would seem to be by running a p i l o t study on the f i n a l d i s -crimination under conditions c l o s e l y approximating those of the experiment, and s e l e c t i n g the point of reversal at a convenient loc a t i o n between the run i n which the slowest learner began to give the instrumental response consistently, and the runs just preceding those i n which the fastest learner begins to manifest a better than 50$ response to the rewarded card. 49 Dealing f i r s t with experimental issues which ar i s e out of the continuity p o s i t i o n attention i s directed to the problem of awareness of the s t i m u l i . F i r s t there must be some means consistent with continuity theory of ensuring that the animals are a c t u a l l y f i x a t i n g the appropriate area of the stimulus card at the moment of response. Ehrenfreund's attempt to do t h i s (5) has been described. This condition must obtain for a s i g n i f i c a n t number of t r i a l s p r i o r to the reversal. Second, and complementary, there must be some means of ensuring that the animals are not f i x a t i n g the ground rather than the f i g u r e . These two conditions a r i s e out of Spence's c r i t i c i s m s (43) of the o r i g i n a l Krechevsky experi-ment. A further condition imposed by Spence i s that the animals must "receive discriminably d i f f e r e n t stimulation" from the beginning of the t r a i n i n g series (42). Precisely what i s meant by this i t i s d i f f i c u l t to i n f e r , and the matter has never been c l a r i f i e d . Without a more precise statement of i t s meaning t h i s condition cannot be regarded as offering an operational issue. Again there must be an avoidance of those factors which tend to the summation and generalization of i n h i b i t -io n , i n order to meet the issues raised by Blum and Blum. Thus punish-ment of the "incorrect" response i s unacceptable, and "non-reward" must be substituted.^ - Massed t r i a l s should also be avoided f o r the learning series, and the correction method which r e s u l t s i n repeated non-reward i s also unacceptable. The problem of stimulus generalization must of course be met as f a r as possible within the l i m i t s of the d i f f i c u l t 1 I t may s t i l l , of course, be argued that t h i s i s a form of punishment, however i t i s the mildest form which i s operationally possible. 50 discrimination required by the non-continuity position. The double pronged stand used by Ehrenfreund meets t h i s requirement t o some extent as f a r as s i t u a t i o n a l cues are concerned. Faster learning with t h i s type of stand has been experimentally demonstrated by Haire (9) and others. Another experimental issue which follows from continuity theory i s that the presence of d i s t r a c t i n g elements during the reversal period w i l l tend to produce a spurious r e s u l t i n favour of the non-continuity prediction. The issue of correction versus non-correction, while included above, merits separate discussion, since the objections to this method go beyond the problem of i t s i n h i b i t o r y effect. Spence has pointed out (43) that the correction method favours the r a p i d elimination of position responses during the f i r s t few t r i a l s , i . e . , those i n which the s t i m u l i are reversed, with consequent d i s t o r t i o n of the error scores before and a f t e r reversal. There are other methodological disadvantages to t h i s technique which have been summarized by Leeper (32), v i z . , that i t results i n unequal weighting of the contribution of each t r i a l i n the t o t a l scores; that the conditions of reinforcement or non-reinforcement vary between i n i t i a l and r e p e t i t i v e t r i a l s ; that the number of t r i a l s i s not controlled, or comparable f o r each animal; and that the d e f i n i t i o n of error i s not consistent from t r i a l to t r i a l . On the whole i t would seem inadvisable to use t h i s technique i n c r i t i c a l experimental studies, e n t i r e l y apart from i t s p a r t i c u l a r r o l e i n the controversy. By comparisicn with the issues just discussed, the r e l a t i v e paucity of experimental issues stemming from the non-continuity position 51 i s probably a measure of the degree to which that point of view has r e -mained inadequately structured. The issues can be reduced to three : the d i f f i c u l t y of the discrimination noted above, the i n v a l i d i t y of f o r c -ing attention to the relevant discriminanda discussed e a r l i e r , and a t h i r d issue which gains added importance i n that i t seems consistently to have been ignored or misunderstood by the opposing workers. This i s the issue raised by the so-called " f i v e point" design of Spence. The essen-t i a l feature of t h i s design i s the induction of a position preference during the preliminary t r a i n i n g , and i t s subsequent t r a i n i n g out, a f t e r the reversal. I t must be i n s i s t e d that the induction of a position preference by means of consistent rewards to a given position stimulus cannot be regarded, as a substitute f o r l a b i l e hypothesis formation i n the sense defined e a r l i e r . I t i s doubtful i f , i n view of the imposing e d i f i c e of experimental evidence i n d i c a t i n g the contrary, any non-continu-i t y t h e o r i s t would wish to deny e n t i r e l y the cumulative effect of reward. The issue, as has been pointed out, does not rest here, but rather with the problem of what i s rewarded. This technique and i t s variants does not then constitute an adequate test of the controversy from a non-continu-i t y point of view. I t follows from the foregoing that an adequate test of the con-troversy would be an experiment designed to meet a l l of the issues d i s -cussed above. Certain factors should however be borne i n mind. F i r s t i s that the s t a b i l i z a t i o n of issues presented here i s appropriate only to the contemporary alignment of the controversy and should by no means be regarded as f i n a l . However i f experiments which f u l f i l the specif-52 ica t i o n s given should repeatedly prove to be inconclusive or inoperable, those which do not are unacceptable as substitutes, and i t must be con-cluded that the controversy i n i t s contemporary form does not present an operational issue. Rationale of the Present Experiment The design of the present experiment i s offered as one which does f u l f i l the conditions of each posi t i o n . Before describing i t how-ever a very b r i e f review of the t h e o r e t i c a l position on which i t i s grounded, together with an analysis of the two relevant previous studies are i n order. The s p e c i f i c t h e o r e t i c a l issue under consideration arises out of possible sources of the controversy. I t i s conceivable that the two theories are describing i d e n t i c a l processes at dif f e r e n t l e v e l s . In t h i s case there i s no r e a l controversy. I t i s also possible that the continuity position i s e s s e n t i a l l y correct for simple situations while the non-continuity position i s appropriate to those which are more d i f f i c u l t . This d i s t i n c t i o n refers to simple versus d i f f i c u l t discriminations per se, that i s , those involving many t r i a l s and errors, as opposed to those in v o l v i n g r e l a t i v e l y few. The weight of evidence would seem to be against t h i s supposition.^ - Another i n t r i g u i n g p o s s i b i l i t y i s that d i s -criminations involving stimulus i n t e n s i t y are adequately described by continuity theory, while those involving perceptual factors are subject to discontinuous learning, i n a sense s l i g h t l y d i f f e r e n t to that ^ I t i s also possible of course that one of the theories i s i n v a l i d . 53 o r i g i n a l l y proposed. I t w i l l be r e c a l l e d that during the review of the his t o r y of the controversy, experiments which tended to favour the l a t t e r p o sition were those involving perception, and were carried out by workers interested i n t h i s aspect of the f i e l d . There i s some "face v a l i d i t y " i n the notion that stimulus i n t e n s i t y i s "binding" on the organism while perceptual organization i s subject to less mechanical causation. In t h i s connection Lashley's term " a l l or nothing basis of learning" while i t seems less than adequate i n i t s o r i g i n a l context, seems p e c u l i a r l y appropriate to the description of perception i n the l i g h t of studies on, e.g., closure. I t i s also i n t e r e s t i n g that Hull's most adequate attempt to quantify the postulate of afferent neural interaction i s l i m i t e d to s t i m u l i on the same physical continuum. (8). I t i s an experimental p o s s i b i l i t y then, that Krechevsky's o r i g i n a l r e s u l t s were due to the fact that h i s stimulus cards were of a type which demand some degree of perceptual organization i n order that they be d i f f e r e n t i a t e d . Indeed these were the i d e n t i c a l cards used by him and by Lashley i n studies on the factor of proximity i n v i s u a l c l o s -ure. I t i s also possible, of course, that his res u l t s were due to the v i o l a t i o n of one or more of the factors which have been discussed as esse n t i a l to an adequate test of the two theories. An experiment which included these factors,., together with Krechevsky's stimulus cards, would, i f p o s itive f o r the non-continuity prediction, i s o l a t e the stimulus cards as the source of these r e s u l t s , and lend some appearance of v a l i d i t y to the t h e o r e t i c a l considerations just discussed, though not to any conclus-54 i v e degree. Such a r e s u l t would, however, conclusively disprove the continuity position as i t now stands, as f a r as the area of perceptual organization i s concerned. I t should be noted that Spence has conceded the p o s s i b i l i t y that S-R theory as now organized i s inappropriate to the problems of perception and has stressed the fact that S-R theorists have not been p r i m a r i l y concerned with t h i s area of behaviour (45). I f how-ever the results of such an experiment were to uphold the continuity prediction i t would conclusively demonstrate the i n v a l i d i t y of the non-continuity position i n what must be more or less i t s l a s t outpost, while lending considerable weight to the adequacy of continuity theory.^ I t i s now appropriate to examine Krechevsky's experiment (24) i n order to ascertain the extent to which i t f a i l s to meet the c r i t e r i a which have been put forward. Spence's c r i t i c i s m that animals tend i n the jumping stand t o f i x a t e the lower part of the card has been noted. The correction method was used and the conventional technique of locking the incorrect door so that responses to i t are punished was also employ-ed. The data afforded three possible comparisons of which only one i s acceptable i n view of the use of the correction method, v i z . , that com-paring t r i a l s a f t e r reversal f o r experimental and control groups. The problem of d i f f e r e n t i a t i n g the effect of d i f f i c u l t y per se, as opposed to d i f f i c u l t y a r i s i n g out of perceptual factors, would remain open to experiment. Although the weight of evidence seems to be against the former, i t i s not conclusive. o I t i s acknowledged, of course, that a single adequate negat-i o n of an experimental proposition establishes the i n v a l i d i t y of the theory upon which i t r e s t s , while a single affirmation of such a propos-i t i o n merely lends an increment to i t s a c c e p t a b i l i t y . 55 L i t t l e more need be said of t h i s experiment, c r i t i c i s m s of which have been summarized e a r l i e r . Continuity theorists explain the results as the outcome of inadequate- f i x a t i o n (Spence) or the effect of i n h i b i t i o n (Blum and Blum); Spence also remarked that i f the figure and ground had been reversed the re s u l t s might have been e n t i r e l y d ifferent since the r a t tends to respond to the brightest portion of the card. Munn's c o l l a t i o n of data from r a t studies does not bear t h i s out (36). I t i s evident that t h i s experiment requires to be re-run i n order to meet these c r i t i c i s m s . Ehrenfreund 1s experiment attempts to do t h i s f o r the problem of f i x a t i o n . This experiment, while i n many ways a model for technique and reporting, i s nevertheless open to serious c r i t i c i s m s . His f i r s t experiment was c a r e f u l l y designed to provide a test s i t u a t i o n the r e s u l t s of which were already foregone on the basis of preliminary experiments. To argue, because he could demonstrate that the effects of inadequate stimulation produced results s i m i l a r to those of Krechevsky, that there-fore Krechevsky's r e s u l t s were due to t h i s factor i s merely invoking an analogy. A further c r i t i c i s m i s that while t h i s i s a discrimination between figures rather than stimulus i n t e n s i t i e s the figures chosen are among the easiest f o r the rat t o learn (35)* Again the use of the pos i t i o n preference method has been shown to be undesirable. There i s also a suggestion, although the report i s ambiguous as this point, that the pre-solution period was defined under the conditions of the d i f f i c u l t s i t u a t i o n of Experiment I . I f t h i s were the case then t h i s series would p a r a l l e l that of Krechevsky's Group I I I . (Indeed i t i s i n t e r e s t i n g that 56 f o r t y t r i a l s reversed t r a i n i n g was the number used for each of these groups.) The in t e r e s t here however centers on the stimulus cards them-selves, and i t i s evident from the considerations outlined e a r l i e r that t h i s experiment requires to be re-run using Krechevsky 1s stimulus cards and retaining Ehrenfreund's precautions against inadequate f i x a t i o n . This i s the experiment which was undertaken by the writer and which w i l l now be described. Apparatus The apparatus was i d e n t i c a l to that used by Ehrenfreund, specifications f o r which w i l l be found i n his a r t i c l e (5)« I t s essen-t i a l features were the double pronged jumping stand (Plate I ) , so con-t r i v e d that i t could be raised or lowered i n r e l a t i o n to the stimulus windows and moved back and forth from a distance of two inches to a d i s -tance of seven inches from them. The windows themselves were s i x inch-es on each side and were separated by a distance of two inches. Illum-i n a t i o n was provided by a goose neck lamp c e n t r a l l y placed so that equal i n t e n s i t y was provided f o r each window, as measured by a standard photo-meter. The goal box was painted white, the rest of the apparatus black, including the non-reward compartment, i n order to avoid generalization of the reward conditions. The stimulus cards were hinged at the base so that they f e l l back e a s i l y when touched by the animal. An e l e c t r i c timer was provided to regulate the reward period and was connected to a lamp which was shielded from the animals i n order to avoid conditioning to t h i s stimulus. A stop watch with a s i l e n t s l i d e was used to time PLATE I Stimulus windows and double pronged jumping stand. The card on the l e f t i s the f i r s t t r a i n i n g card of the series. 58 latencies. Controls In addition to those implied above, a number of s p e c i f i c con-t r o l s were employed. Munn (36) l i s t s f i v e requirements of discriminat-ion learning experiments,- ( i ) The order of stimulus presentation must be randomised. This was accomplished by selecting from Gellerman's table (6) ten series to meet the following c r i t e r i a . No series contain-ed more than two i d e n t i c a l positions i n succession. There were at least two ri g h t s and two l e f t s i n both the f i r s t and l a s t h a l f of each series of ten. Each series contained only f i v e reversals of l e f t - r i g h t or r i g h t - l e f t . Each series offered only chance reward to either single or double alternation of position responses. These c r i t e r i a were also met inncombining the series. ( i i ) Irrelevant cues must be removed. A l t e r -nate pairs of stimulus cards were provided. The jumping stand was scrubbed frequently each day and the goal box and non-reward boxes were cleaned d a i l y , i n addition to controls mentioned above. ( i i i ) The pos-s i b i l i t y of the animals hearing the stimulus cards changed must be elim-inated. The reward and non-reward boxes were arranged such that by appropriately s h i f t i n g them the s t i m u l i were changed (see Plate I I ) . These boxes were shifted a f t e r each t r i a l regardless of the stimulus re-l a t i o n s , ( i v ) The experimenter must be behind the animals during t h e i r runs. This was f u l f i l l e d . (v) Giving of cues by manual guidance of the animals must be avoided. This was tested by having a strange operator handle the animals from time to time. In addition to these 59 PLATE I I Goal box (center) and alternate non-reward compartments. 60 controls the apparatus was provided with additional panels (see Plate I I I ) shielding the jumping stand. Illumination i n the room was constant, and d i f f e r e n t i a l brightness was controlled by removing objects which would provide these cues and by the arrangements of the room and the ap-paratus . Controls were also involved i n the feeding and care of the animals. The weight of each animal was checked frequently and feed was apportioned such that weight loss was kept r e l a t i v e l y constant. Two animals were kept on ad l i b feeding throughout the experiment as a check on food intake and weight. Since there was considerable v a r i a t i o n i n the weight and s i z e of the animals d i f f e r e n t i a l feeding was regarded as the best means of ensuring r e l a t i v e l y constant motivation. The temperat-ure of the room containing the cages was regulated by means of heaters and a d a i l y record of maximum and minimum temperature was kept. During the actual running of the experiment the animals were caged singly. The di e t was a balanced r a t i o n provided by the Animal Husbandry Depart-ment . Plan of Procedure Forty Albino r a t s , twenty male and twenty female, from four 100-day l i t t e r s of the Wistar s t r a i n were trained as follows,- On the f i r s t day'" the animals were placed on the stand and allowed to "explore" The term "day" i s used throughout t h i s section to denote a complete run of a l l the animals. In practice t h i s frequently occupied two days owing to the large number of animals. In general, males and females were run on alternate days. The order of running was preserved from day to day. PLATE i n Apparatus from i n front. The window on the l e f t i s open to the white goal box. The stand i s raised as i n Ehrenfreund's Experiment I I . 62 the apparatus. The white goal box was accessible through the open win-dow on the r i g h t , while the non-reward window was closed with a black card. The jumping stand was placed so that there was a two inch gap l e v e l with the lower edge of the window. Each animal was allowed t o enter the goal box and eat for s i x t y seconds. On the second day t h i s procedure was repeated with the goal box on the l e f t , thus affording some ind i c a t i o n of i n i t i a l preferences. From t h i s point the procedure was as follows : (1) Three days t r a i n i n g (30 t r i a l s ) with the apparatus arrang-ed as above; animals allowed to eat for f i f t e e n seconds i n the open goal box; t r i a l s spaced t h i r t y seconds apart. In t h i s phase the animals are learning what i s e s s e n t i a l l y a brightness discrimination. (2) On the fourth day the gap was widened to three inches on the f i r s t t r i a l f o r every animal. Subsequently, since the animals varied i n s i z e and l e v e l of a c t i v i t y , the gap was widened for each animal on successive t r i a l s as soon as each animal had successfully crossed a given gap. This t r a i n i n g was continued to a l i m i t of eighty t r i a l s , a f t e r which the few animals which had not yet mastered the f i n a l gap of seven inches were given extra t r i a l s . I t w i l l be seen that t h i s procedure res u l t s i n over-training of the faster learners. I t was adopted i n order to avoid having a group of animals out of contact with the apparatus for a f a i r l y long period of time. I t was also f e l t that the varying degrees of t r a i n i n g , when equated i n control and experimental groups, would afford i n t e r e s t i n g cross comparisons. 63 (3) A stimulus card, the upper three-quarters of which was white and the lower area black, was now substituted f o r the open window and the stand was raised so that i t was l e v e l with the lower edge of the white portion (see Plate I, p. 57) • From t h i s point on, t r i a l s were spaced. This card was alternated with the open window (stand lowered) for eight t r i a l s , balancing the random order of stimulus presentation with t h i s alternation. This was followed by four successive t r i a l s to the card. Animals which were performing u n s a t i s f a c t o r i l y at the end of the eight alternate t r i a l s were given additional balanced alternation of card and open box before continuing. (4) The area of the white part of the card was now reduced at a rate suitable to each animal u n t i l each would jump to a rectangle, one and three-quarter inches by two and a quarter inches, placed d i r e c t l y i n front of the raised stand. This was done i n an e f f o r t to t r a i n out the avoidant tendency t o the black ground of the card. (5) The next step was to divide the animals into experimental and control groups on a random basis using a standard table of random numbers (4), and checking for the significance of differences between rate of learning the brightness discrimination, rate of learning t o jump the gap and to knock over the card, percentage weight l o s s , and d i v i s i o n of the sexes and l i t t e r s , i n order to ascertain that the a l l o c a t i o n of these factors could i n practice be attributed to chance. (6) F i n a l l y the experimental stimulus cards (see Plate IV) : J PLATE IV Fi n a l stimulus cards with an animal approaching. The stance i s t y p i c a l of the "scrambling" behaviour of an animal refusing to jump. 65 were to be presented i n accordance with the reward reversal design. In the absence of a sat i s f a c t o r y p i l o t study, the reversal period was to have been set at t h i r t y t r i a l s . This t r a i n i n g would have been continued to an adequate c r i t e r i o n of mastery. Description of Procedure While the preceding section outlined the plan of the experiment a statement of the procedure would be incomplete without some description of the animals' behaviour. This w i l l follow the outline of the proced-ure. On the f i r s t two days of the experiment a l l the animals located the food i n the goal box after varying lengths of time on the stand. (1) The behaviour of the animals during the f i r s t t h i r t y t r i a l s was very uneven p a r t l y owing to inadequate control of motivation. In spite of the careful precautions i n feeding, the animals l o s t weight at widely varying rates. This i s a function of skin area (area of heat loss) and of varying degrees of maturity within the r e s t r i c t e d age range. Eleven of the animals mastered the discrimination within the t h i r t y t r i a l s . ( F i r s t of ten successive t r i a l s without error or two successive days with only one error i n each day.) (2) During the t r a i n i n g t o the gap, motivation had become more For a l l p r a c t i c a l purposes the experiment was discontinued at t h i s point f o r reasons presented i n the next section. 66 even. A problem was raised by the tendency of the animals to f a l l i f the gap were too wide. I t was found that having once f a l l en very few animals would attempt the same gap again, and i t would have to be closed to a point at which the animal would again respond. This i s probably accounted for i n part by the technique of t r a i n i n g by which, i n accordance with the design, no pain or anxiety producing inducements to jump were employed. In a "continuity" frame of reference t h i s r e s u l t could be predicted from the steep l i n e a r curve f o r summation of i n h i b i t -ion as opposed to the og i v a l curve for summation of excitation r e s u l t i n g i n rapid accumulation of i n h i b i t i o n with the introduction of a punishing factor. An inte r e s t i n g feature of t h i s phase was that f o r each animal there was a point at-which i t could no longer step or walk Over the gap, but must adopt the r a d i c a l l y d i f f e r e n t muscular set involved i n jumping. Presumably the molecular description of t h i s behaviour would involve a decrease i n the excitatory potential of the open window i n e l i c i t i n g the new response, while the view which emphasizes d o c i l i t y and e q u i f i n a l i t y would postulate a l a b i l e adaptation to the new s i t u a t i o n . The subject-ive impression was that l i t t l e loss was occasioned. However, i t could also be argued that the effect of i n h i b i t i o n noted above would be sharp-ened by such a l o s s , i n conformity with the observed behaviour noted previously. That i s to say, the decrease i n excitatory potential of the window at t h i s point was added to the summation of i n h i b i t o r y p o t e n t i a l generated by f a l l i n g as an additional factor preventing repet-i t i o n of the response. Obviously the measurement of t h i s factor would require a rigorously controlled s i t u a t i o n , and measures more sensitive 67 than those available here. After eighty t r i a l s fourteen of the animals had not yet learned to cross the seven inch gap and s i x of the animals had not mastered the brightness discrimination. These were given add-i t i o n a l t r a i n i n g . (3) The f i r s t presentation of the white stimulus card presum-ably takes advantage of the transfer of t r a i n i n g from the white square v i s i b l e through the open window to the white card. In practice there was a tendency f o r the animals, after the f i r s t exposure of the card, to either refuse the jump or to jump i n such a way that they f e l l . I t was found that t h i s could be overcome by presenting the card and window a l -ternately for a few t r i a l s . I t w i l l be noted that t h i s behaviour and the stimulus conditions which overcome i t are both highly consistent with molecular continuity theory i n terms of stimulus equivalence and the generalization continuum. I t i s not, however, inconsistent with the opposing view. (4) The next step i n the procedure i s made necessary by the fa c t that the animals have been consistently trained t o avoid the black card. The procedure of reducing the area of white was arrived at em-p i r i c a l l y using a pair of the animals as a p i l o t group. The technique was successful within l i m i t s . However i t was during t h i s phase that the animals began to develop the behaviour which made i t necessary to discontinue the experiment. As the area of white was decreased there was an increasing tendency for the animals to jump "wild", i . e . , to miss the window and f a l l into the net below. Having once made such a jump 68 the tendency was to repeat the f a u l t y jump and to continue doing so u n t i l the animal had f a l l e n a s u f f i c i e n t number of times that i t would no long-er respond. Numerous attempts at "therapy 4 1 were undertaken, the most successful being to return the animal to an e a r l i e r phase i n the t r a i n -i n g, and i n a few t r i a l s repeat the steps which had preceded the inad-equate responses. This procedure was eventually adopted routinely as soon as a f a u l t y jump occurred. Before this technique had been develop-ed, however, eight of the animals had developed highly stereotyped jumps and were discarded. Four more animals developed these stereotyped i n -adequate responses i n spi t e of immediate r e t r a i n i n g . x (5) and (6) A tentative d i v i s i o n of the remaining animals i n t o experimental and control groups yielded two groups which were free of s i g n i f i c a n t v a r i a t i o n s . However, when the remaining animals were present-ed with the experimental discrimination the same type of behaviour devel-oped. I t would seem merely prodigal of space and time to record here the various attempts which were made to overcome t h i s tendency. The f i n a l technique, the rationale of which i s evident, was to substitute a card which was intermediate between the two stimulus cards, i . e . , had an equal number of squares equally spaced and opposed to the black card. This was further buttressed by adding to the center of the card a white patch the same si z e as that to which the animal would jump. While t h i s was the most successful technique, and one to which twenty of the animals responded, the tendency to jump "wild" continued. When the c r u c i a l pair of cards was f i n a l l y presented, only four of the animals continued to 1 Eight animals died during the experiment, a mortality rate of 17$. 69 respond a f t e r nine t r i a l s , with intervening sessions for "therapy". While i t would have been possible t o continue, allowing the animals to f a l l to the net and then be placed by hand i n the food box or non-reward box as appropriate, i t i s evident that such a technique would have i n -volved a drast i c reduction i n controls, an increase i n irrelevant s t i m u l i , and, not l e a s t , the i n v a l i d a t i o n of the no punishment requirement essen-t i a l to the experiment. At t h i s point, therefore, the experiment was discontinued. Analysis of Possible Causes of Failure While i t would be unprofitable to devote much space to t h i s topic i t i s at lea s t not irre l e v a n t to speculate on some of the causes of the behaviour just described. F i r s t i s the obvious p o s s i b i l i t y that the v i s u a l acuity of the animals was inadequate to the task. Not only were the animals albinoes, a circumstance which could not be avoided, but there was no way of adequately checking for the presence of con-ge n i t a l v i s u a l defects other than microphthalmia which was absent."'" I t might be noted too that s e l e c t i v e factors i n the breeding of these animals had been directed at t h e i r s u i t a b i l i t y f o r n u t r i t i o n studies, rather than f o r learning studies. These factors might i n themselves account f o r the wide range of performance i n learning the i n i t i a l bright-ness discrimination. Also since the behaviour of some of the animals i n the apparatus i n the l a t e r t r i a l s resembled i n i t s stereotypy the behaviour Dr. A. J. Wood, Department of Animal Husbandry, U.B.C 70 of rats i n an insoluble discrimination, i t seems possible that these animals were not receiving adequate stimulation. The degree of stereo-typy was curiously exemplified by one animal which would jump and f a l l , and which learned unaided to climb back to the rjumping stand where i t would repeat the jump. This cycle of behaviour would continue u n t i l the response had been exhausted, and would be continued after a period of res t . Another p o s s i b i l i t y which should not be overlooked i s that the o r i g i n a l avoidant t r a i n i n g to the ground of the f i n a l stimulus card presented a learning situation which was too f i n e l y equilibrated t o be susceptible of mastery by the animals. I f t h i s i s the case i t i s d i f -f i c u l t to surmise what alternative method would ensure that the animals do not f i x a t e the ground during reversal. A further p o s s i b i l i t y with a s i m i l a r bearing i s that a discrimination design of t h i s complexity i s simply not soluble i n the absence of some technique f o r forcing the jump and for some punishment of the inappropriate response. I t should be born i n mind that the jumping stand with these two features enabled Lashley to obtain discriminations which had thitherto been considered im-possible, t h i s at a time when the learning dynamics were not a major source of i n t e r e s t . I t may be merely naive then to denude Lashley's technique of two of i t s features, and then to expect learning of a d i f -f i c u l t discrimination to occur. In t h i s connection i t i s i n t e r e s t i n g that an experiment, undertaken recently at the University of C a l i f o r n i a , encountered a problem s i m i l a r to the one encountered here i n that some 71 60$ of the animals jumped wild. I t might be noted that t h i s experiment used hooded rats and did not attempt the figure-ground controls employed here. I f i t i s the case that an experiment involving a discrimination s u f f i c i e n t l y d i f f i c u l t t o s a t i s f y the requirements of non-continuity theory cannot be performed without punishment factors, i t follows from the previous discussion that there i s not at present a v a l i d operational d i s t i n c t i o n between the two theories. x Oral communication from Mr. Wyers, Assistant, Department of Psychology, U. of C. CHAPTER V RESULTS Descriptive Analysis of Data While the use of the term " r e s u l t s " , i n the l i g h t of the preced-ing disclosures, i s purely gratuitous there are one or two areas of i n t e r -est i n the data collected up to the conclusion of the experiment. These data include records of t r i a l s and errors for the i n i t i a l brightness discrimination, mastery of the seven inch gap, and performance during the card presentations, a rather impure measure of latency for each t r i a l , records of "therapy" t r i a l s , a b r i e f description of behaviour f o r each t r i a l (organized i n seven discrete categories), and a record of percent-age weight loss f o r each animal at selected periods during the series. Not a l l of these are of i n t e r e s t . However, i t i s i n t e r e s t i n g t o attempt an analysis of the data, i n the absence of conclusive experimental r e s u l t s , bearing i n mind the two theories discussed. While t h i s cannot be present-ed as experimental evidence, i t constitutes, perhaps, a useful matrix of observations. F i r s t a b r i e f s t a t i s t i c a l description of the course of the experiment may be of i n t e r e s t . The preference exhibited on the f i r s t two days were as follows : r i g h t going, four animals; l e f t going, eight animals; dark-preference, nineteen animals; brightness preference, seven animals; not inferred, two animals. Thus twelve of the animals 73 had i n i t i a l p o sition preferences, while twenty-six animals had phototaxic preferences. This tabulation assumes of course that no responses were due to random factors, and i s probably highly contaminated. The brightness discrimination was learned i n an average of 37*75 t r i a l s , with a range from 2 to 114 t r i a l s , and S.D. of 27«4» Three of the animals learned t h i s discrimination i n less than ten t r i a l s . The average number of t r i a l s required to master the s even inch gap, from the t r i a l at which the gap was enlarged, was 44-08, with a range from 8 to 86, S.D. of 13*8 (N = 34)* There was more v a r i a t i o n i n the number of t r i a l s required to learn the gap a f t e r mastery of the i n i t i a l b right-ness discrimination, average being 34«73 with range from 34 to 84, S.D. of 29*2. This range includes negative values f o r four animals who mastered the seven inch gap before the discrimination had been learned. I f either of these functions were dependent upon the other or on a common factor some positive correlation would be expected between the number of t r i a l s to learn the brightness discrimination, and the number required to master the gap. ,An i n s i g n i f i c a n t product moment correlation of .33 i n -dicates the unlikelihood of a common factor. On the other hand, i f learning of the two tasks interfered with one another the rate of mastery of the gap f o r those animals which learned the discrimination before the introduction of the gap (N = 13) would d i f f e r from that of those animals which learned after i t s introduction. While there i s a difference of t r i a l s favouring the former group, i t i s not s i g n i f i c a n t (t = .59). I t i s of some int e r e s t to know i f a relationship i s involved i n these measures since by the rationale of continuity theory the effect of 74 introducing the gap would be s l i g h t l y to retard learning of the d i s -crimination by reducing the excitatory potential of the stimulus f o r the new response. S i m i l a r l y the learning of the gap would be retarded by the reduced tendency to make the response under these conditions. I t i s of course possible that a re l a t i o n s h i p of t h i s kind i s masked by the extreme v a r i a b i l i t y , as suggested by the i n s i g n i f i c a n t difference i n t h i s d i r e c t i o n . An i n t e r e s t i n g comparison i s that between animals which refused to jump on the f i r s t presentation of the reduced white area on a black ground and those which responded. I t w i l l be re c a l l e d that one of the suggested causes of the breakdown of the jumping response was the presence of black to which an avoidant response had been learned. I f t h i s were the case, then overtraining to the brightness discrimination would presum-ably bear a relationship to the f a i l u r e to respond."*" Since the continu-ous variable representing the number of t r i a l s of overtraining i s hap-hazardly d i s t r i b u t e d , i n a roughly trimodal form, i t i s not feasible to attempt a correlation. However, the f a i l u r e s are f a i r l y evenly d i s t r i b u t -ed along the continuum, suggesting that t h i s i s not a s i g n i f i c a n t factor. Interestingly enough when these groups are compared on the number of t r i a l s of overtraining i n jumping the seven inch gap i t i s found that of the 14 animals f a i l i n g , 10 had had 19 or more t r i a l s overtraining, while only 4 had had 14 or l e s s . The d i s t r i b u t i o n of these t r i a l s i s also f a r x In t h i s t r i a l a more drastic reduction of the white area was presented than was used i n subsequent t r i a l s , and i t seems u n l i k e l y that the higher response tendency to the white would offset the avoidant ten-dency to the black, although t h i s remains a p o s s i b i l i t y . 75 from normal, but an approximate notion of the relationship may be obtain-ed by a r b i t r a r i l y d i v i d i n g the subjects into two groups representing two populations and determining the significance of the proportion of f a i l u r e s i n each group. I f the animals are divided into those f a l l i n g above, and those f a l l i n g below, the median f o r overtraining to the gap, i t i s found that 59$ of the former group f a i l e d to make the c r u c i a l response, while only 26$ of the l a t t e r group also f a i l e d . These proportions are s i g n i f -i c a n t l y d i f f e r e n t at the 5$ l e v e l of confidence (two t a i l e d t e s t , cor-recting f o r the continuity of the measure). The mean number of t r i a l s overtraining f o r the two groups thus a r b i t r a r i l y formed are 26.23 and. 13.53 respectively, t h i s difference being s i g n i f i c a n t at the 1$ l e v e l of confidence. A s i g n i f i c a n t difference (5% l e v e l of confidence) also exists between the proportion: of f a i l u r e s i n the group l y i n g above the midpoint of the range, and i n that l y i n g below the midpoint. These two a r b i t r a r y groups received an average of 38.40 and 1 6 . 5 0 .trials over-t r a i n i n g respectively. While a very crude comparison, these figures suggest that the greater the degree of overtraining to the jump, the les s the l i k e l i h o o d that i t would be performed under altered stimulus conditions, regardless of the amount of overtraining to the discriminat-ion. I t i s not without i n t e r e s t that these findings p a r a l l e l the general Hull-Spence position of continuity theory, and tend to be i n opposition to a theory, such as that of Krechevsky or Tolman, which emphasizes l a b i l i t y of the response i n terms of means-end expectancies. (There i s no question here of a response to the incorrect card. The usual behaviour of these f a i l u r e s was to run to the correct prong of the 76 stand where they would scramble and hesitate but refuse t o jump.) I t i s stressed of course that the foregoing observations are i n no way re-garded as experimental evidence, and are made pri m a r i l y for t h e i r i n -terest value. Analysis of Error Scores There i s a further area of the data which seems to present i n -te r e s t i n g p o s s i b i l i t i e s for analysis. Before turning to t h i s analysis the rationale on which i t rests w i l l be presented i n some d e t a i l i n or-der to f a c i l i t a t e c r i t i c i s m of i t s postulates. I t w i l l be remembered that Krechevsky's o r i g i n a l formulation of the concept of "hypotheses" resulted from an analysis which assumed that no responses were the r e -s u l t of chance factors, i n opposition to the notion of "random" t r i a l and error. The re s u l t of t h i s analysis was to present an "error curve" f o r various systematic position responses which was compared to the con-ventional error curve representing solution of the discrimination. A "chance zone l i m i t " (50$ + ?>/t!Q) was set and i t was shown that f o r the - ^  N e a r l i e r t r i a l s the curve representing p o s i t i o n "errors" f e l l outside the chance zone, while the error curve f o r brightness hovered within the chance zone l i m i t . In the l a t e r t r i a l s the position curve rose to chance, while the error curve dropped. On t h i s evidence i t was con-cluded that during the systematic position responses the animals were not responding to brightness. There i s an erroneous implication, at least i n a casual interpretation of these r e s u l t s , that the curve for brightness, l i n g e r i n g at the chance l e v e l , i s an independent function 77 free to vary with respect to the position curve and remaining i n the chance zone as a r e s u l t of the chance l e v e l of response to brightness which the curve seems t o represent. x In point of fact the two curves are of course r e c i p r o c a l , due to the structuring of the presentation of the s t i m u l i , which presents an equal number of randomly alternated positions of the "correct" card. In other words, i n any given sequence the number of responses to a given position i s necessarily related to the number of "correct" responses. Thus, for example, i f i n a series of ten, there are nine r i g h t going responses (however determined) four of them must necessarily be to the "incorrect" card, and the tenth or l e f t response may be either correct or incorrect, so that the error score must be either s i x or four, depending on the disposition of the remain-in g response. In any systematic series of position responses then, there i s a necessary l i m i t t o the possible error scores. For convenience of reference, these l i m i t s are presented i n Table I, which shows the pos-s i b l e d i s p o s i t i o n of scores for any given number of r i g h t going responses between f i v e and ten i n a series of ten responses. (A ri g h t going response l e v e l of four i s of course equivalent to a l e f t going l e v e l of si x . ) The scores are broken down in t o r i g h t bright (RB), r i g h t dark (RD), l e f t bright (LB),- and left-dark (LD). Dark going combinations (RD, LD) represent conventional errors, and are summated i n column 5> giving the possible error scores for the series (E). The number of ri g h t going responses gives the name to the category f o r each table. That misunderstandings of th i s process have occurred i s evidenced i n Haire's treatment of the Spence theory (9)' 78 TABLE I POSSIBLE DISPOSITIONS OF ERROR SCORES FOR GIVEN CATEGORIES OF POSITION RESPONSES # CATEGORY 10 CATEGORY 9 RB RD LB LD E RB RD LB LD E 5 5 0 0 5 5 4 1 0 4 4 5 0 1 6 CATEGORY 8 CATEGORY 7 RB RD LB LD E RB RD LB LD E 5 3 2 0 3 5 2 3 0 2 4 4 1 1 5 4 3 2 1 4 3 5 0 2 7 3 4 1 2 6 2 5 0 3 8 CATEGORY 6 CATEGORY 5 RB RD LB LD E RB RD LB LD E 5 1 4 0 1 5 0 5 0 0 4 2 3 1 3 4 1 4 1 2 3 3 2 2 5 3 2 3 2 4 2 4 1 3 7 2 3 2 3 6 1 5 0 4 9 1 4 1 4 8 0 5 0 5 10 # The possible disposition of position responses for given error scores may also be deduced from the Table by switching column headings. 79 I t w i l l r e a d i l y be seen that the higher the number of responses to a given p o s i t i o n the fewer the possible error scores. This perhaps over laborious presentation of the obvious merely serves to i l l u s t r a t e the fact that the curve for position responses and the curve f o r brightness responses are r e c i p r o c a l l y related without necessarily representing a r e c i p r o c a l r e l a t i o n between the two functions measured. I t w i l l also be seen that where ten, nine, or eight r i g h t going responses occur, i n any series of ten, the error score cannot f a l l higher than seven or low-er than three, that i s , i t must remain within the apparent "chance zone l i m i t . " I t i s also evident that f o r these categories the chance zone l i m i t i s spurious with regard to the brightness scores, since there i s permitted only a narrow l a t i t u d e of v a r i a t i o n . The true chance d i s t r i b u t -ion within t h i s l a t i t u d e i s a function of the number of possible combin-ations which w i l l produce the respective error scores. For example, where eight r i g h t going responses occur an error score of three can i only be given by the occurrence of two LB responses, and s i m i l a r l y an error score of seven can only arise out of the occurrences of two LD responses. Within the series of ten, however, an error score of f i v e may r e f l e c t either the sequential combination LD-LB or LB-LD giving two p o s s i b i l i t i e s of occurrence. Thus the chance d i s t r i b u t i o n of responses for the error scores 3> 5, and 7, would be 1:2:1. S i m i l a r l y for other categories, summarised i n Table I I , p. 80. Thus i t follows, since the stimulus conditions are pre-arranged to avoid any systematic relationship between position and brightness, that i f the animals are a c t u a l l y responding at a chance l e v e l to bright-TABLE I I PROBABILITY OF CHANCE OCCURRENCE OF THE ERROR SCORES PRESENTED IN TABLE I CATEGORY 10 CATEGORY 9 Error Scores Error Scores 4 6 Chance D i s t r i b u t i o n 0 Chance Di s t r i b u t i o n 1 : 1 CATEGORY 8 CATEGORY 7 Error Scores 3 5 7 Error Scores 2 4 6 8 Chance Dis t r i b u t i o n 1 : 2 : 1 Chance Dis t r i b u t i o n 1 : 3 : 3 : 1 81 ness during those series of t r i a l s i n which responses to a given position are s i g n i f i c a n t l y high, the d i s t r i b u t i o n of t h e i r error scores should be i n accord with the p r o b a b i l i t i e s outlined. Armed with these deductions i t i s appropriate to turn now t o an analysis of the data accumulated f o r the i n i t i a l brightness discrimination. The data are presented i n Table I I I which f i r s t requires a word or two of explanation. The f i r s t column represents the subjects by rank, the second by code number, while the succeeding columns represent blocks of ten t r i a l s corresponding with the "days" of this phase of the experiment. The t o t a l number of responses" to l e f t or r i g h t on each day, whichever i s higher, i s given on the l e f t of the column, the number of errors, i . e . , dark going responses i s given on the r i g h t . The correspondence by days i s not exact since after t r i a l 80 those animals which had learned the discrimination"and had mastered the seven inch gap were rested while the slow learners were continued. Thus t r i a l s 81-100 for the former group represent the f i r s t twenty successive jumps to the card (Phase 3)« For the slow learners t r i a l s 81-130 represent a d d i t i o n a l t r a i n i n g . T r i a l s 101-130 include only those animals which had not yet learned the discriminat-i o n . The post solution t r i a l s to a l i m i t of 100 are presented i n order to provide a summary of behaviour a f t e r the mastery of the discrimination. The c r i t e r i o n f o r learning i s ten successive t r i a l s without error, or two successive days with only one error i n each day, unless i t i s obvious from the succeeding t r i a l s that since (a) the calculation of the S.D. i s loaded with the scores at the s i g n i f i c a n t extremes, and (b) i t i s custom-ary i n non-continuity practice to l a b e l as "hypotheses", any series of &4 t r i a l * R s 1 1-10 li-20 21-30 1 20M j 6R 1 5 0 5 0 2 13 1 6R 1 5 0 5L 0 3 13M I 6R 1 •v 5 0 7R 2 k 3 7R 2 6R 3D ' 0 5 Hi 5 2 5 0 5 0 6 11 7L 2 6R 1 5 0 7 2CP 7R 2 6L 1 5 0 8 h 6L 1 5 2 5 0 9M 10R 5 f 7R 2 6L 1 10 12M 6L' 7 8L 3 6R 1 11 19 5 U 6R 3 5 0 , 12 2M 5 0 "J 8R 5 7R l i 13 liM 6R l / 5 2 5 2 Hi 6 7R 2 6R 1 5 2 15 10 5 2 8R 3 6L 5 16 IliM 5 2 7R 2 8R 3 17 5M 8R 7 ; 8R 3 7L 2 18 8 6R 3 6R 3 6L 3 19 19M 7R 2 5 6 6R 1 20 3M 7L li 6L 3 7R 0 21 15M 5 I 6L 1 7L 2 22 16 7R 6 7R 2 6L 1 23 17M 9R li 6R 3 6R 3 2k 18M 9R li 10R 5 6R 1 25 1 6L 1 6R 3 6R 3 26 5 5 2 5 2 6R 3 27 8M 8R 7 7L U 6R 3 28 11M 5 0 5 0 8R 3 29 7M 8R 7 6R 3 6L 3 30 15 8L 5 10L 5 5 2 31 17 7R 6 7L 6 7R 2 32 16M 8R 5 6R 3 7R 2 33 7 6R 7 8L 3 6L 5 3U 9 8R 3 9R U 6L 3 35 12 8R 3 6R 1 6R 1 36 1M 5L 2 10R 5 6L 5 37 2 6L 5 8R 3 7L U 38 10M 7R l i 6R 5 7R !» 39 18 8R 3 9R li 5 2 ! 31-I+0 5 o 5 2 l l l l 0 0 0 1 '6R 6L 6L 6L 5 5 5 5 5 6L 6L 6R 7L 6L 6L 5 5 L 5 6R 7R 8L 6L 6R 8R 5 5 6R 5 6L 6R 5 7L 5 9R 6R 0 0 1 1 1 2 3 3 2 2 2 3 2 5 3 3 3 2 U 1 2 3 7 2 6 l i 6 3 Ui -50 6R 5 6L 5-5 6L _6a. 5 5 5 6L 5 6R 5 5 6R L6L 5 5 5 5 5 6R 7L 5 8R 7R 6R 6R 5 10L 8R 8R 7R 5 5 8R 7R 1 ©J 1 0 0 1 6 0 0 3 0 1 0 0 1 1 1 0 0 0 0 0 1 li 2 3 2 1 3 0 5_ 3 5 2 2 0 5 l i 51-60 5 5 6L 6R 5 6R 5 5 5 6R 6L '6"L 6R 7L 5 5 5 6 L 6R 6R 5 6R 5 6R 0 2 1 5 0 1 0 0 0 1 1_ " i l 2 0 0 0 1 1 1 0 3 2 1 6L 6R 6R 7R 7R 7R 8R 6R 7R 1 1 3 2 2 li 3 1 6 JL 7R 2 5 2 6R 5 5 10 6L 5 61-70 5 6R 6L 9R 5 6L 5 5 5 6R 6L 6L 6L 7L 5 6L '6L 6R 5 5 5 0 1 1 li 0 1 0 0 0 1 1 1 1 2 0 1 r 1 0 0 0 + 6L 1 5 o 6L 1 6R 1 6R 5 7R 10L 7R 6R 7L 6L 7R 5 6B 5 7L 1 0 2 5 2 3 l i 3 l i 0 5 2 li 71-80 V » \ 5 5 5 5 5 6L 5 6L 6L 7R 5 8L 6L 7L 5 5 5 6L 5 6R 6L 0 0 0 li 0 l 0 1 1 2 0 3 1 2 0 0 0 1 0 1 1 5 2 5 _o 6L 1 5 o 5 o 6w 1 5R 6L 6R 5 6R 6R 5 7L 6L 6L 8R 0 1 1 6 1 1 li 2 5 l 7 81-90 7L 2 5 0 5 0 + 5 5 6L 5 7L 5 • 6L 5 7 L 5 6L 0 0 1 0 1 0 1 0 1 0 1 . + 6L 1 5 o 5 o 6R I 5 5 5 o o 2 5^  o + 7L. 2 6R 1 _5 D_ 5 6L 5 7R 0 3 2 2 9R l i 5 2 + 6L. 3 91-100 5 6R 5 5 5 5 6R 6L 5 5 5 6R 5 5 5 5 5 7L 5 5 5 5 5 6E 5 6R 6R 5 7R 0 1 0 0 0 0 1 3 o o o 1 0 0 0 0 0 2 0 0 2 0 0 6L 1 5 2 5 2. 7R 1 101-110 111-120 82 121-130 P i 1 0 1 1 ii 5 0 7L 2 5 5 . l i 6L 7R 2 6R Q2 n • j 1 | 8R 9/3 0/3 0/3 e/3 o/3 0/2 oA 0/3 oh 0/2 o/5 2/5 0/3 0/3 1/3 °£ oA ° £ oA 2/3 oAo oA 2/8 0/3 0/3 % 0/3 1/2 2 A l Table I I I : showing the performance of each subject i n block of ten t r i a l s 83 responses which are f a i r l y consistent ( i . e . , an "hypothesis" i s of course not thought of as coming into existence just at the point at which the curve crosses the 3 sigma l i n e ) . The operational issue, then, l i e s i n the d i r e c t i o n and degree of departure, i f any, of the error scores from the chance d i s t r i b u t i o n which i s to be expected i f , during the appearance of position "hypo-theses", the animals are a c t u a l l y "ignoring" brightness cues, as the non-continuity position asserts. The description given by continuity theory leads to the prediction that the error scores w i l l d i f f e r from chance i n the dire c t i o n favouring a response tendency to brightness, since the animal's response tendencies from t r i a l to t r i a l are regarded as a function of the combined excitatory p o t e n t i a l of a l l the stimulus elements present. The technique of the analysis i s to select a l l the instances during the pre-solution period i n which the operation of a position response during a run of ten t r i a l s may be inferred from the l e v e l of response to r i g h t or l e f t . The technique could be extended to "alternating", "double alternating", "perserverative hypotheses", and so on, but for the present purpose of demonstration the choice has been l i m i t e d to l e f t and r i g h t going "hypotheses". The t e n - t r i a l units have been l i m i t e d to the series representing "days" on the assumpt-ions that t h i s sample represents the data, that i t avoids the inclusion of day to day variations i n running conditions, and i n order to avoid duplications or overlapping. Results are presented i n Table'IV for 9, 8, and 7 po s i t i o n responses respectively, the l a t t e r category being i n -cluded because, while not s i g n i f i c a n t as a departure from the chance zone 84 TABLE IV FREQUENCY OF OCCURRENCE OF POSSIBLE ERROR SCORES PERMITTED BY THE OCCURRENCE OF 9, 8, OR 7 POSITION RESPONSES IN TEN TRIALS CATEGORY 9 (6 cases) (1) Error scores 4 or 6 (2) Theoretical frequency 1 1 (3) Observed frequency 5 1 (4) f t % 50 50 (5) fo % (rounded) 83 17 CATEGORY 8 (24 cases) (1) Error scores 3 5 7 (2) f t 1 2 1 (3) fo Ik 6 4 (4) f t % 25 50 25 (5) f o % 58 25 17 CATEGORY 7 (43 cases) (1) Error scores 2 4 6 8 (2) f t 1 3 3 1 (3) fo 25 12 6 0 (4) f t % 12.5 37-5 37-5 12.5 (5) fo % 52 25 13 0 85 l i m i t i t i s consistent with, the general notion of "hypothese" and contains error scores which do remain within the chance zone. The question which i s asked of these r e s u l t s i s : When there i s a momentary departure from the "hypothesis", what i s i t s d i r e c t i o n and what i s i t s degree? The answer to t h i s question may throw some l i g h t on the issues which have been discussed. An examination of Table IV reveals consistent departures from chance i n the d i r e c t i o n of the lowest error score for each category. Distributions i n each category y i e l d highly s i g n i f i c a n t values of c h i -squared at the 1% l e v e l of confidence, that for Category 9 being of course questionable owing to the small number of cases. While t h i s t e s t of significance does not take account of d i r e c t i o n , i t i s obvious by i n -spection Tvhere the major contribution l i e s . These results would seem, granting the assumptions of the analysis to o f f e r rather s t r i k i n g con-firmation of the continuity prediction i n a simple brightness discriminat-ion. The p o s s i b i l i t y that the majority of animals were responding on the basis of two c o n f l i c t i n g hypotheses w i l l be dealt with i n consider-ing i n d i v i d u a l scores.''* A further prediction of the continuity p o s i t i o n , i s that t r i a l s during the e a r l i e r phases of learning the discrimination would produce less tendency to low error scores, than those during the l a t t e r I t should be noted that t h i s analysis does not represent an "ad hoc" reduction of the data, since the prediction i s clear before the technique of analysis i s applied, and the analysis i s applied to a l l cases. This i s not hoxvever true of the next section as noted i n the te x t . 86 phase. Table 7 presents the data arranged f o r the f i r s t quarter of the pre-solution period, the second quarter and the l a s t h a l f . The t h i r d and fourth quarters are not shown separately owing to the drop i n number of "position hypotheses" during t h i s l a t t e r phase. The f i r s t and second quarters are therefore combined i n Column 3 as a comparison. I t w i l l be seen that the trend i s i n the direction predicted by continuity theory. This i s p a r t i c u l a r l y exemplified i n passing from the f i r s t quarter to the second quarter (Columns 1 and 2) and from the f i r s t h a l f to the second hal f (Columns 3 and k)> None of these d i s t r i b u t i o n s y i e l d s i g n i f i c a n t values of chi-squared when tested for independence, so that t h i s breakdown of the data can only be regarded as being suggestive of conformity to the prediction. Nevertheless, i t i s i n t e r e s t i n g t o speculate on the drop i n proportion of bright going responses i n the l a s t h a l f (cf. Columns 2 and /».)• I t has so far been assumed that the position l e v e l was the main determinant of the l i m i t -a t i on i n error scores f o r each category. This assumption was merely f o r convenience i n c l a r i f y i n g the presentation. More rigorously the expression of position tendencies i s regarded i n continuity theory as a combined function of the strength of the response to the given position stimulus, and the gradually increasing response tendency to the consist-ently rewarded brightness stimulus. Thus the appearance of a given l e v e l of position responses i n any ten t r i a l series may either be a function of high excitatory potential i n the position stimulus, or r e l a t i v e l y low values i n the brightness stimulus, the actual responses from t r i a l t o t r i a l being a function of both these factors. I t i s TABLE V THEORETICAL AND OBSERVED DISTRIBUTION OF ERROR SCORES DURING THREE PHASES OF THE PRE-SOLUTION PERIOD 01 02 01 & 02 03 & Q4 CATEGORY 9 ( l ) Error Scores 4 6 4 6 4 6 4 6 (2) f t 1 1 1 1 1 1 1 1 (3) fo 4 0 0 1 4 1 1 0 (4) f t % 50 50 50 50 50 50 50 50 (5) fo % (rounded) 100 0 0 100 80 20 100 0 CATEGORY 8 ( l ) Error Scores 3 5 7 3 5 7 3 5 7 3 5 7 (2) f t 1 2 1 1 2 1 1 2 1 1 2 1 (3) fo 5 2 3 6 3 0 11 5 3 3 1 1 (4) f t % 25 50 25 25 50 25 25 50 25 25 50 25 (5) fo % 50 20 30 66 33 0 55 25 15 60 20 20 CATEGORY 7 ( l ) Error Scores 2 4 6 8 2 4 6 8 2 4 6 8 2 4 6 8 (2) f t 1 3 3 1 1 3 3 1 1 3 3 1 1 3 3 1 (3) fo 3 5 3 0 9 1 1 0 25 12 6 0 13 6 2 0 (4) f t % 12.5 i 37-5 37-5 12.5 12.5 37-5 37-5 12.5 12.5 37-5 37-5 12.5 12.5 ; 37.5 ; 37.5 12, (5) fo % 27 45 27 0 82 9 9 0 58 28 14 0 62 28 10 0 0> —•3 88 therefore possible that animals which develop high position values dur-ing the second h a l f of the pre-solution period are those whose rate of acqu i s i t i o n of the brightness response has been slow, with consequent p i l i n g up of position tendencies, as opposed to animals whose position tendencies i n the f i r s t h a l f are the main determinant of the l e v e l of pos i t i o n response with consequent masking of the brightness response. Note that t h i s i s not a d i s t i n c t i o n between fast and slow learners per se, but between two populations of learners, those whose position respons-es are c h i e f l y a r e f l e c t i o n of high position tendency, and those whose pos i t i o n responses are expressed p r i m a r i l y as a r e s u l t of the r e l a t i v e l y slow rate of acquisition of the brightness response consistent with varying slopes for the ogi v a l curve representing t h i s function i n con-t i n u i t y theory. Two trends i n the data would bear t h i s out. ( l ) I f the animals contributing high position l e v e l s i n the s econd h a l f were a di f f e r e n t population from those contributing high po s i t i o n levels i n the f i r s t h a l f . Table I I I indicates that t h i s i s act u a l l y the case, with the exception of three animals out of the four slowest learners. (2) I f the contribution of error scores f o r the t h i r d quarter were higher than those f o r the fourth quarter. This breakdown i s shown i n Table VI for category 7, the only one having a s u f f i c i e n t number of cases to j u s t i f y the demonstration. The di r e c t i o n of the trend i s appropriate i n each column, and bears out the tentative hypothesis that these scores may represent animals whose position responses are the result of a depressed gradient i n the curve f o r the acquisition of brightness tendencies, with consequent 89 TABLE VI DISTRIBUTION OF ERROR SCORES IN THE THIRD AND FOURTH QUARTERS OF THE PRE-SOLUTION PERIOD FOR CATEGORY 7 03 (1) Error Scores 2 4 6 (2) f t 1 3 3 (3) fo 7 5 2 (4) f t % 12.5 37-5 37-5 (5) fo % 51 36 14 04 8 2 4 6 8 1 1 3 3 1 0 6 1 0 0 12.5 12.5 37-5 37.5 12.5 0 85 15 0 0 90 fortuitous p i l i n g up of p o s i t i o n tendencies. I t i s again emphasized that none of the results presented i n Tables V and VI represent s t a t i s t i c -a l l y s i g n i f i c a n t differences. The discussion has been presented merely to show that the d i s t o r t i o n of the trend toward lowering of the error scores during learning i s not necessarily inconsistent with continuity theory. These results also gain i n t e r e s t through the rather high degree of consistency i n the temporal trend toward the p i l i n g up of error scores i n a rank order of frequency under each column. Obviously, i n view of the r e l a t i v e infrequency of cases i n the s i g n i f i c a n t categories, t h i s type of analysis demands a very large number of subjects. While i t i s u n l i k e l y that the analysis stands or f a l l s by the comparison of i n d i v i d u a l scores, since the assumptions on which i t rests are commonplace enough, i t i s relevant to examine the i n d i v i d u a l perform-ance i n Table I I I . I t must be remembered that results f o r i n d i v i d u a l animals cannot possibly be s i g n i f i c a n t owing to the small number of units involved; indeed, t h i s i s one o r i g i n of the controversy. However, certain indicators may be sought. For example, i f the ten t r i a l s f o l -lowing the expression of a position "hypothesis" usually contain an error score below f i v e , i t w i l l be an indication of the trend expressed i n the analysis. Inspection of Table I I I shows that t h i s i s almost i n -v a r i a b l y the case, p a r t i c u l a r l y beyond the f i r s t ten t r i a l s . Subjects ranked 9 (9M) 15 (10) and 24 (IBM.) are e s p e c i a l l y i n t e r e s t i n g i n t h i s connection since they present position responses levels of ten successive t r i a l s . I t w i l l be seen that number 36 (1M) contradicts the expected trend and presents a peculiar picture generally. Another indication i s 91 found i n the position responses which occur after solution of the d i s -crimination. The general pattern of the analysis i s upheld i f error scores here f a l l i n the lowest category permitted by the position l e v e l . Inspection of the table w i l l show that t h i s i s the case, with the notable exception of-the animal ranked 4 (3)' One further comparison i s of i n t e r e s t . From Table I I I the scores of i n d i v i d u a l animals can be read to determine the number of errors occurring at various l e v e l s of position response f o r each animal. I t would be possible but extremely laborious to calculate the combined p r o b a b i l i t i e s for each animal. On the other hand a summation of bright and dark favouring responses would ignore the p r o b a b i l i t y weighting of s p e c i f i c values. An approximation may be achiev-ed by simply adding the amounts by which the error scores exceed 5 and the amounts by which the error scores are less than f i v e separately f o r each animal. This information i s contained i n the l a s t column of Table I I I fo r p osition levels of 9, 8 and 7' The numerator represents amounts above f i v e , the denominator amounts below f i v e , the continuity predict-io n being that the numerator w i l l usually be the smaller value. The d i s t r i b u t i o n of the scores during the successive t r i a l s can be read f o r each animal. These r a t i o s again support the continuity position. I t i s also of interest i n inspecting the table to notice that the f i r s t ten t r i a l s of Day 1 indicate a preponderance of either bright or dark going responses, with few at the 50$ l e v e l , ^ probably i n d i c a t i n g that even i n ^ The data have not been presented by days because t h i s d i v i s -io n , beyond the point noted, offers no new findings, and i s more a r t i -f i c i a l than that adopted i n Table IV. The trend i s consistent however when the analysis i s made. 92 these very early t r i a l s the animals were responding to t h i s element of the stimulus complex. Summarising t h i s section i t i s suggested that the proper evalu-ation of error scores accompanying high l e v e l s of position response rests not with the significance range of ten responses but with the l i m i t e d range permitted by the l e v e l of po s i t i o n responses. Analysis of these scores asks the question : When an animal departs from a high l e v e l of position responses, i s the departure most frequently to the positive or to the negative stimulus of the discrimination problem? Since stimulus conditions are arranged to provide random va r i a t i o n between position and brightness, i t follows that i f the error scores are actual-l y the product of chance these departures w i l l be approximately equal toward the po s i t i v e and negative s t i m u l i . Highly s i g n i f i c a n t variations from chance are found for position l e v e l s of 7, # and 9 responses out of ten i n the d i r e c t i o n favouring the continuity prediction.^ - I t must be r e a l i z e d of course that t h i s analysis i s highly a r t i f i c i a l i n that i t ignores the fa c t o r of response sequence, and assumes that summated scores represent the tendency of a l l animals, a usage which i s nevertheless general i n animal learning experiments. I t would seem then that the view which regards the learning of a simple discrimination as a process i n which the animals, when respond-i n g to position aspects of the stimulus complex, are ignoring or not responding to brightness aspects as w e l l , represents an inadequate view x I t need hardly be said that t h i s i s also true for categories 6 and 5« 93 of such learning; and that the apparent chance l e v e l of the "correct" response during position dominated series of t r i a l s i s a spurious effect of the structuring of the stimulus sequences, and does not represent a chance l e v e l of functioning. The p o s s i b i l i t y remains that the scores r e f l e c t the performance of those animals which were responding on the basis of two c o n f l i c t i n g hypotheses."1" I f t h i s i s the case, an inspect-ion of Table I I I would seem to indicate that very nearly a l l of the animals are included i n t h i s category, and none may d e f i n i t e l y be ex-cluded. Further, the conditions of the experiment were not those which would force the animals to attend to the relevant discrirainanda from the beginning. The question arises then, which theory provides the more precise description of the discrimination learning process i n the s i t u a t i o n of the present experiment. I t would seem that the theory which predicts the results obtained i s preferable to that which can merely be applied after the fact and i n a modified form. The continu-i t y theory predicts these r e s u l t s , for a simple discrimination, without equivocation. The foregoing analysis, together with the rationale on which i t i s based, are presented therefore as demonstrating the adequacy of the central proposition of continuity theory f o r a simple brightness discrimination. I t i s suggested that t h i s method of analysis might p r o f i t a b l y be applied to more complex discriminations, using large groups of subjects and meeting the requirements outlined e a r l i e r . I t i s the """ I t might be noted that t h i s problem does not a r i s e i n con-nection with position l e v e l s 8, 9 or 10, since the error scores are within the "chance zone l i m i t " . The concern i s with the remaining t r i a l s . 94 writer's opinion that t h i s experiment would be preferable to the reversed pre-training experiment as a c r u c i a l t e s t of the opposed theories since the problem of defining an acceptable point of reversal does not a r i s e . Before leaving these data one other point w i l l b r i e f l y be mentioned. The continuity theory describes the appearance of system-a t i c and consistent responses to the appropriate s t i m u l i as being a function not only of the gradual accumulation of excitatory p o t e n t i a l to the appropriate s t i m u l i , but also as a function of the equalization of pos i t i o n tendencies. I t follows that for the a r b i t r a r y c r i t e r i o n chosen here, which does not demand 100$ l e v e l of responses, the t r i a l s of the two days following, mastery of the c r i t e r i o n w i l l be approximately normal i n d i s t r i b u t i o n of the number of position responses, with the mean at 5 responses to each position. I f such a te s t y i e l d s a d i s t r i b u t i o n pre-ponderantly favouring either r i g h t or l e f t responses the operation of a systematic factor can be assumed. I f however the d i s t r i b u t i o n i s symmetrical i t strongly suggests that position responses are randomly allocated, since the l i k e l i h o o d of a precise balance between subjects retaining r i g h t going and l e f t going tendencies i s very s l i g h t under the conditions of the experiment. The interest of the following data derives c h i e f l y from t h e i r s t r i k i n g conformity to the predicted d i s -t r i b u t i o n . The frequency of 8, 7, 6, 5, 4, 3 and 2 r i g h t going responses during the twenty t r i a l s following attainment of the c r i t e r i o n was 0, 2, 12, 32, 12, 2, and 0, respectively. The Spence Assumptions . One further area of potential interest i n the data concerns 95 the measure of latency. There i s an implication i n Spence's table for a hypothetical discrimination learning series, that i f latency be ac-cepted as a measure of the strength of the momentary response tendency, then the latencies f o r the respective stimulus element combinations w i l l be arranged i n rank order determined by the r e l a t i v e strength of each component. For example, an animal i n a given t r i a l whose strongest position tendency was r i g h t and whose strongest tendency was to bright-ness, would, before these tendencies became evident i n systematic responses to brightness.,, present the following relationship among latencies : RB<cLB«c:RD«=:LD. Thus, i f the r i g h t going tendency were s u f f i c i e n t l y high to mask the bright going tendency the RD latencies when a negative card coincided with the r i g h t position would be longer than the RB latencies i n which the p o s i t i v e card was presented on the r i g h t . And since these tendencies are assumed to be f a i r l y stable f o r series of t r i a l s , the latency curve f o r each animal for each t r i a l would contain markedly serrated portions. The appearance of t h i s feature i n the data collected i n the present experiment i s rather frequent and s t r i k i n g , p a r t i c u l a r l y when combined with behavioural observations i n -dicating that during the prolonged latencies the animals appeared to be "exploring" "washing" etc., but only on those t r i a l s i n which the i n -appropriate s t i m u l i were combined, the.other t r i a l s being d i r e c t . I t would of course be highly inappropriate merely t o select these instances as evidence, and suggest that the design was obscured for other subjects and t r i a l s . The data were rather exhaustively analysed but f a i l e d to show s i g n i f i c a n t differences (e.g., the prediction that latencies f o r LB 96 and LD responses would be correlated, that there would be a correlation between RB and LB responses, that the variance of the latency measure would be greater i n the t r i a l s immediately preceding mastery than i n those on equal preceding periods, etc.)* The p o s s i b i l i t y of t e s t i n g these and s i m i l a r predictions remains open, however, since the latency measure here i s very crude and contains, f o r error t r i a l s , the time spent returning from the incorrect to the correct window on the double stand. I t i s suggested that a controlled study i n t h i s d i r e c t i o n might prove i n t e r e s t i n g and that the differences might be increased by placing a m i l d l y charged g r i d before each window. A direct approach to the continuity assumptions concerning combination of stimulus elements was made aft e r the conclusion of the experiment, the design of which w i l l be b r i e f l y described. Fourteen animals whose jumps to the small white square were sa t i s f a c t o r y and who had had considerable overtraining to brightness were placed i n the stand and presented with two equal white squares (one and three-quarter by two and a quarter inches) on a black ground. They were rewarded on whichever side they jumped. They were then given f i v e rewarded t r i a l s on t h i s side a f t e r which they were tested for strength of the position response by determining the amount of increase i n area of white on the non preferred side that was necessary to induce a jump to t h i s side. Training was given for ten t r i a l s to an upright as opposed to an inverted e q u i l a t e r a l t r i a n g l e (two inches base) randomly alternated to right and l e f t , the upright t r i a n g l e being consistently rewarded. During these t r i a l s responses were consistently to the preferred side. They were 97 then tested again, half the animals with the upright t r i a n g l e f i r s t and inverted t r i a n g l e second for any change i n area of white necessary to induce a response to the non preferred side. These series of ten t r i a l s , followed by test were continued. The prediction of continuity theory i n t h i s s i t u a t i o n i s clear-l y that as the number of rewarded t r i a l s to the upright t r i a n g l e i n -creases, and before systematic responses to brightness are evidenced, the area of white necessary to induce the non preferred position response with the positive figure on the preferred side w i l l increase, while there w i l l be a decrease i n the area of white required to induce the departure i n the presence of the negative figure on the preferred side. I t w i l l be seen that the design i t s e l f i s based on continuity theory. The test for strength of the position habit had previously proven efficaceous, f i v e animals requiring an increasing amount of white on the non preferred side as t r a i n i n g to that side continued, and a decreasing amount as non reward of the preferred p o s i t i o n accumulated. In t h i s connection i t was observed that fewer t r i a l s were required to produce a stable position response than to t r a i n i t out. Results of t h i s procedure tended i n the d i r e c t i o n predicted. However i n view of the f a i r l y large number of t e s t i n g t r i a l s required between t r a i n i n g t r i a l s to establish the relationships, the s i t u a t i o n was not w e l l controlled. In addition to t h i s the animals again develop-ed spoiled jumps, and as the t r a i n i n g proceeded the number of animals dwindled. For this reason the actual data are not presented here. The p r i n c i p a l i n t e r e s t of t h i s experiment was i n demonstrating the 98 relationship between previously acquired position and brightness cues as being roughly equivalent to the continuity description. I t i s f e l t that t h i s type of design,.which i s too crude here even to j u s t i f y d i s -cussion of r e s u l t s , might very e a s i l y be refined by the use of e l e c t r i c -a l l y controlled continuous gradations of brightness, possibly i n a hurdle discrimination, and naive subjects. The technique would afford d i r e c t comparisons of the r e l a t i v e strength of each stimulus component at selected points throughout the learning, and would not have to be l i m i t -ed to p o s i t i o n trained animals. The writer believes that i f more experiments of t h i s type were run, i n which a descriptive prediction i s made from theory, and the description empirically quantified, at vary-ing levels of complexity, there would be less l i k e l i h o o d of controvers-i a l pseudo-issues appearing i n the l i t e r a t u r e . I t i s suggested that non-continuity theory would benefit by t h i s type of experimentation, before further d i r e c t tests involving a c o n f l i c t of r e s u l t s between the two theories are attempted. CHAPTER VI SUMMARY AND CONCLUSIONS Summarising r a t h e r . b r i e f l y the foregoing material the following points appear relevant. The continuity controversy o r i g i n a l l y concerned the issue of continuous versus discontinuous learning of the f i n a l s t i m u l i i n discrimination situations. Subsequent refinements were i n -troduced, among others the issues of awareness or attention, the roles of i n h i b i t i o n and generalization, and the issue of successive as opposed to simultaneous hypothesis formation, p a r t i c u l a r l y as related to the com-p l e x i t y of the s i t u a t i o n . Experimentally the test which was found most acceptable was the reversed pre-training discrimination which appeared to y i e l d clear cut predictions but which was found to y i e l d contradictory r e s u l t s . P a r a l l e l i n g the refinement of theory was the introduction of a number of experimental issues the most important of these concerning the receptor orientation of the animals i n the early phases of learning, the necessity of providing a discrimination s u f f i c i e n t l y d i f f i c u l t that two or more hypotheses must be tested, the avoidance of any technique which forces attention to the relevant discriminanda from the beginning of learning, and the necessity of avoiding punishment factors i n the t r a i n i n g of the animals. Various writers reviewing the experimental l i t e r a t u r e have put forward suggestions as to i t s significance. Among the more cogent of these are the suggestions that experiments using a 100 simple discrimination, or those using a minimum of punishment techniques, or those involving a low l e v e l of sensory dominance and perceptual organ-i z a t i o n have tended respectively to favour the continuity prediction while those involving the opposites of these conditions have tended to favour the opposing view. Among suggestions offered as to the nature of the controversy there has been some stress recently on the view that the issues have been oversimplified, on the view that each of the theories are i n r e a l i t y presenting descriptions of i d e n t i c a l processes at d i f f e r -i ng l e v e l s , and the view that each theory may be appropriate to a d i s -crete range of events. Consideration might also be given by way of summary to the view that, as Underwood (46) suggests, the r o l e of the yes-no controver-sy i n psychology may represent an immature stage of theory development. From the standpoint of Learning Theory i t would seem that an answer, to the controversy i t s e l f i s , i n a f i n a l analysis, rather less important than the elaboration of each theory, and the r e f e r r a l of each theory separately t o empirical tests appropriate to i t s constructs. In th i s process, the non-continuity theory has lagged. This i s not, however, s u f f i c i e n t ground on which t o reject i t , e specially since i t contains germinal hypotheses whose f i n a l adequate acceptance or r e j e c t -i o n i s extremely important f o r psychology. That such a l a g need not 0 be the case i s perhaps suggested by Brunswick's treatment of theory construction (3) i n which bases f o r extending the systematic development of t h i s type of theory are suggested. An experiment i s described i n which an attempt was made to 101 t e s t the p o s s i b i l i t y that Krechevsky "s r e u l t s i n his o r i g i n a l reversed pre-training experiment (24) were due to the s p e c i f i c nature of the f i n a l stimulus cards. This was to have been effected by c a r e f u l l y eliminating those aspects of Krechevsky's technique which were object-ionable i n terms of recent statements of continuity theory. I t was not possible t o complete t h i s experiment and the suggestion i s made that i f experiments of t h i s design prove to be inoperable, as did the present one, then the operational v a l i d i t y of the controversy must be held i n question. F a i l i n g results from the scheduled experiment the data of the i n i t i a l brightness discrimination are analysed and are found to favour with s i g n i f i c a n t differences the prediction of continuity theory, for a simple brightness discrimination. A l i m i t e d number of conclusions consistent with the material presented may be drawn. ( l ) I t would seem to be f a i r l y evident that the o r i g i n a l statement of non-continuity theory must be modified i f i t i s to be ac-cepted as an adequate description of learning. The weight of experiment-a l evidence, including that presented here, does not seem to j u s t i f y the notion that those responses to a single stimulus component i n a simple  quantitative discrimination which precede systematic responses to the relevant stimulus components represent a period of learning during which reward of the f i n a l cues i s i n e f f e c t i v e . I t should be noted that non-continuity theory does not predict but merely admits the p o s s i b i l i t y of, simultaneous hypotheses being formed i n learning such a discriminat-ion, and that the objection to the reversed pre-training design i n 102 simple discriminations i s merely that t h i s process may occur with con-sequent retardation of learning i n the reversed group. (2) -From an operational standpoint i t must be conceded that the adequacy of a modified non-continuity theory for discriminations involving complex perceptual organizations of s t i m u l i has not been adequately tested. I t i s suggested that the most p r o f i t a b l e re-evalu-ation of the non-continuity theory might be directed at t h i s range of events. (3) I t must be concluded on the basis of the present survey that an experimental test which i s designed to provide clear cut and c o n f l i c t i n g r e s u l t s f o r each theory cannot be said to have been perform-ed unless i t meets the c r i t e r i a presented i n Section IV ( l ) of this study. I f experiments which do f u l f i l these c r i t e r i a should prove, as did the present one, to be inoperable or to give inconclusive results i t must be concluded that the controversy as i t i s presently formulated does not provide an operational issue. REFERENCES Blum, R.A., and Blum, J.S. Factual issues i n the "continuity controversy". Psychol. Rev.. 1949, 56, 33-50. Brogden, W.J. Animal studies of learning. In Handbook of experimental psychology (Ed., Stevens, S.S.). New York: John Wiley and Sons, Inc., 1951, 568-612. Brunswick, E. The conceptual framework of psychology. Inter- national Encyclopedia of Unified Science. Chicago: Univers-i t y of Chicago Press, 1952. Edwards, A.L. Experimental design i n psychological research. New York: Rinehart and Co. Ltd., 1950. Ehrenfreund, D.J. An experimental t e s t of the continuity theory of discrimination learning with pattern v i s i o n . J . comp.  Psychol., 1948, 41, 408-432. Gellerman, L.W. Chance orders of alternating s t i m u l i i n v i s u a l discrimination experiments. J . genet. Psychol., 1933, 42, 206-208. Grice, G.R. The acq u i s i t i o n of a v i s u a l discrimination habit f o l -lowing responses to a single dimension. J . exp. Psychol., 1948, 38, 633-642. Haire, M. A note concerning McCulloch's discussion of discriminat-ion habits. Psychol. Rev., 1939, 46, 298-303-Haire, M. Some experimental data r e l a t i v e to f i e l d and associat-ive theories of discrimination learning. J . genet. Psychol., 1942, 26, 267-288. Harlow, H.F. The formation of learning sets. Psychol. Rev., 1949, 56, 51-65-104 Harlow, H.F. Analysis of discrimination learning by monkeys. J . exp. Psychol., 1950, 40, 26-39. H u l l , C.L., and Spence, K.W. Correction versus non-correction method of t r i a l and error learning i n r a t s . J . comp. Psychol., 1938, 25, 127-145-H u l l , C L . The discrimination of stimulus configurations and the hypothesis of afferent neural interactions. Psychol. Rev., 1945, 52, 133-142. H u l l , C L . Simple q u a l i t a t i v e discrimination learning. Psychol.  Rev., 1950, 57, 303-313. Krechevsky, I . Hypothesis i n r a t s . Psychol. Rev., 1932, 39, 516-532. Krechevsky, I . "Hypothesis" versus "chance" i n the pre-solution period i n sensory discrimination learning. Univ. C a l i f . Publ. Psychol., 1932, 6, 27-44-Krechevsky, I . The genesis of hypotheses i n r a t s . Univ. C a l i f . Publ. Psychol., 1932, 6, 45-64-Krechevsky, I . , and Tolman, E.C Means-end readiness and hypo-thesis - a contribution to comparative psychology. Psychol.  Rev., 1933, 40, 60-70. Krechevsky, I. The docile nature of "hypothesis". J. comp.  Psychol., 1933, 15, 429-441-Krechevsky, I . The hereditary nature of "hypotheses". J. comp.  Psychol., 1933, 16, 99-116. Krechevsky, I. Brain mechanisms and "hypotheses". J. comp.  Psychol., 1935, 19, 427-462. Krechevsky, I. A note concerning "the nature of discrimination 105 33* McCulloch, T.L., and Pratt, J.G. A study of the pre-solution period i n weight discrimination by white r a t s . J. comp. 106 Psychol., 1934, 18, 271-290. McCulloch, T.L. Comment on the formation of discrimination habits. Psychol. Rev.. 1939, 46, 75-85-McCulloch, T.L. Reply to a note on discrimination habits. Psychol. Rev., 1939, 46, 304-307-Munn, N.L. Handbook of psychological research on the rat. Boston: Houghton M i f f l i n Co., 1950. Prentice, W.CH. Continuity i n human learning. J . exp. Psychol., 1949, 39, 187-194-Rethlingschafer, A. The learning of a v i s u a l discrimination problem under varying motivating conditions. J . comp. Psychol., 1941, 32, 583-591-Ritchie, J . An experimental attack on the continuity controversy. J. comp. Psychol., 1950, 43, 170-180. Spence, K.W. The nature of discrimination learning i n animals. Psychol. Rev., 1936, 43, 427-449-Spence, K.W. The d i f f e r e n t i a l response i n animals to s t i m u l i varying within a single dimension. Psychol. Rev., 1937, 23, 77-100. Spence, K.W. Gradual versus sudden solution of discrimination problems by chimpanzees. J. comp. Psychol., 1938, 25, 213-224. Spence, K.W. Continuity versus non-continuity interpretations of discrimination learning. Psychol. Rev., 1940, 47, 271-288. Spence, K.W. An experimental t e s t of the continuity and non-con-t i n u i t y interpretations of learning. J . exp. Psychol., 1945, 35, 253-266. 107 45- Spence, K.W. Cognitive versus S-R theories of learning. Psychol. Rev., 1950, 57, 159- . 46. Underwood. Learning. In Annual review of psychology. Stanford: Annual Reviews, Inc., 1953-47' Wherry, R.J. F a c t o r i a l analysis of learning dynamics i n animals. J . comp. Psychol.. 1939, 28, 263-272. 

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0106474/manifest

Comment

Related Items