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The effects of infantile handling and sensory deprivation on adult avoidance learning in the rat Marvin, Jeffrey 1970

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THE EFFECTS OF INFANTILE HANDLING AND SENSORY DEPRIVATION ON ADULT AVOIDANCE LEARNING IN THE RAT by Jeffrey Marvin B.Sc. (Honours), McGill University, 1S58 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS in the Department of Psycnology we accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA Apri l , 1970 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f t h e r e q u i r e m e n t s f o r a n a d v a n c e d d e g r e e a t t h e U n i v e r s i t y o f B r i t i s h C o l u m b i a ^ . I a g r e e t h a t t h e L i b r a r y s h a l l m a k e i t f r e e l y a v a i l a b l e f o r r e f e r e n c e , a n d s t u d y . I f u r t h e r a g r e e t h a p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y p u r p o s e s may be g r a n t e d by t h e H e a d o f my D e p a r t m e n t o r by h i s r e p r e s e n t a t i v e s . I t i s u n d e r s t o o d t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l n o t be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . D e p a r t m e n t o f Psychology  T h e U n i v e r s i t y o f B r i t i s h C o l u m b i a V a n c o u v e r 8, C a n a d a D a t e 30 A p r i l 1970 ABSTRACT Two groups of rats* handled on days (1-11) and days (21-32), and a nonhandled group were tested at 75 days of age on a modified two-way shuttle avoidance task. One-half of the animals were light-reared j the other half dark-reared. Measures taken included percentage correct avoidance responses (AE), intertrial interval responses (ITIE), escape response and avoidance response latencies (EEL and AEL) , and A-Scores in percentage form (AE - ITIR). No differences in any of these measures except EFL was observed as a result of handling, though rearing in differential environments provided significant differences in A E , A-Scores, and E E L . Ee suits were interpreted in terms of several relevant theories, with Melzack's (1968) hypothesis proving the most parsimonious in accounting for the data. i i TABLE OF CONTENTS Page ABSTRACT 1 LIST OF TABLES i i i LIST OF FIGURES iv ACKNOWLEDGEMENT v INTRODUCTION 1 METHODS Subjects . . . . . . . 6 Handling 7 Apparatus and Training Procedure . . . . . . . 8 RESULTS . Avoidance Responses . . . . . . . 10 Intertrial Interval Responses 12 A-Scores . . 13 Escape Response Latency 14 Avoidance Response Latency . . . . . . . 14 DISCUSSION 20 SUMMARY . . . . . . . 31 REFERENCES 33 iii ! LIST OF TABLES Page TABLE I. Summary of results on various measures obtained by experimental and control groups .. 10 TABLE II. Analysis of Variance tables for the five measures 11 ) iv LIST OF FIGURES' Page FIGURE 1. Percentage correct avoidance responses over blocks of 40 trials, all groups 15 FIGURE 2. Percentage correct avoidance responses collapsed across handling treatment levels, LR vs DR . . . . . . . . 16 FIGURE 3. Average number of ITIR over blocks of 40 trials, handling treatment levels combined 17 FIGURE 4. Percentage A-Scores collapsed across handling treatment levels, LR vs DR 18 FIGURE 5. Escape response latencies over blocks of 40 trials, all groups 19 V A CK NOW-LEDGE ME NTS The author wishes to. acknowledge the large contribution made to this thesis in the form of advice and encouragement by Dr. Rod Wong and by Dr. Richard C. Tees of the Department of Psychology at the University of British Columbia. Special thanks are extended to Dr. Tees for his generous assistance regarding apparatus and animal subjects. Statistical help was kindly given by Dr. J , Johnson and by Dr. William Petrusic, also of the Department of Psychology. I should like at this time to acknowledge with gratitude the time and effort expended on the author's behalf by M r . B i l l Coshow of the Computer Center at the University of British Columbia. Finally, I should like to thank my wife, Joyce, for her constant encouragement and infinite patience. ERRATUM On pp. 15, 16, 17 and 18, the word "blocs" should be read "blocks". INTRODUCTION Theoreticians like Hebb (1949) have emphasized the importance of early learning in the life of an organism. Indeed, the theoretical struc-ture of earlier writers such as Freud (1965) depended upon the importance of early learning in the development of the personality and cognitive capa-bilities of man. The methods utilized by experimenters to test such a hypothesis generally involved the addition of some sort of stimulation in some period of the animal*s life, or the subtraction of "normal" stimulation by rearing the animals in a "deprived" environment (Denenberg, 1968). At a later date, the experimental animals were compared to controls on any number of tasks in an attempt to isolate variables affected by the experimental procedure. In these studies, it was important to maintain a high degree of control over the environments of both control and experimental animals to ensure comparability across conditions (King, 1958). Too often, variables unaccounted for in the experimental procedure reduced the reliability of results. These included age of infantile stimulation (Den-enberg, 1968),. age at testing, and the method for testing the persistence of the effects (Denenberg and Bell , 1960), as well as the genetic background of the animals (Levine and Wetzel, 1963), housing conditions (Ader, 1965; McMichael, 1966), and specific husbandry conditions (Denenberg and Whim-bey, 1963). 1 2 There are a number of hypotheses posited to account for the changes in behaviour subsequent to infantile manipulation (i .e. , the addition or sub-traction of sensory stimulation from the environment). These are closely related to Scott's (1962) "critical period" hypothesis which postulated that an organism passes through a number of well-defined critical periods during which appropriate stimulation determines later adult behaviour (see also Hess, 1959). Denenberg's "monotonicity" hypothesis (Denenberg, Morton, Kline, and Grota, 1962; Denenberg and Kline, 1964)stated that stimulation at a certain period of an organism's development results in a decrease in emo-tionality responsiveness in adulthood, facilitating performance on "emo-tion-producing" tasks, such as avoidance tasks. However, too much stimu-lation in infancy produced an emotionally unresponsive adult whose perfor-mance on these tasks was thereby impaired. Denenberg's (1968) work was mainly concerned with animals exposed to increased stimulation in infancy. Thus any significant differences in adult behaviour were attributed to the infantile experience. Similarly, it might be predicted that certain kinds of infantile sensory deprivation would have the same effect; that is , "deprived" animals should differ significantly from "normal" animals on certain beha-vioural indices. Melzack (1965) suggested that much of the behavioural incapacities of 3 adulthood which resulted from infantile deprivation were due to deficient arousal control. In a stressful situation, this led to hyperarousal which made it difficult for the animal to cope with the bewildering array of stimuli presented to him by a novel environment (Melzack and Burns, 1965). Mel -zack's hypothesis might be broadened further to include the effects of infan-tile stimulation, rather than deprivation. If the assumption is made that infantile manipulation modifies the animal's normal ability to integrate pat-terns of behaviour, that is to control his arousal level such that response-selecting mechanisms are not rendered dysfunctional (Hebb, 1955), then it can be said that animals handled in infancy should excel over nonhandled ones on tasks where arousal factors are of prime importance. Riesen (1961, 1966) placed less emphasis on a deficiency in the general arousal system of the deprived organism. He suggested that the behavioural differences noted in the deprived adult animal were probably due to a more specific problem of the lack of perceptual and cognitive processes themselves. Riesen noted that "at least three or four levels of associative integration are involved in the changed courses of development that various restrictions of afferent input impose on the nervous system" (Riesen, 1961, p.80). In the present study, it is mainly the visual and (partially) the auditory systems which are deprived of stimulation. Past studies (Tees, 1968, 1969) revealed that such deprivation had little effect on complex discrimination learning and 4 activity in the rat. However, the task utilized in the present study is marked-ly different from the ones used by Tees. Hence, different results might be expected. Schaefer (1968) interpreted the handling phenomenon in terms of a "temperature" hypothesis. Earlier studies (Denenberg and Karas, 1960; Thompson and Schaefer, 1981) had found a critical period for the handling effects within the first week of the rat's life, a time when the pup is deaf, blind and hardly mobile (Small, 1899). Accordingly, any effects on adult emotionality would have to be mediated through the sensory capacities of this functionally immature creature which are limited to gustatory, olfactory, temperature, tactile, and kinesthetic stimuli. Schaefer's studies focussed on the temperature sensitivity of the rat pup for, as young mammals are unable to regulate their own body temperature, it might be postulated that young animals subjected to handling treatments underwent a change in body temperature. Animals separated from their mother during the handling situation are subjected to differing ai i temperatures which could provide " supranormal" stimulation via temperature receptors in the skin. Accor-ding to Schaefer (1968b, p. 10): If a temperature change accompanying handling is sufficient to lower body temperature in an infant rat, ongoing, tempera-ture-sensitive, enzymatic reactions involved in the develop-mental processes are likely to be affected. This could pro-5 du.ce permanent effects in developing physiological structures or processes which underlie emotionality and stress reacti-vity. The hypotheses of Denenberg, Melzack, Riesen and Schaef er all con-cur in one respect - and that is that infantile stimulation or deprivation results in significant differences from control in adult learning ability and behavioural capacities. These theorists differ essentially in their analysis of the variables responsible for the changed behaviour. The present study was designed to more accurately pinpoint such variables. According to the above hypotheses (Denenberg, 1968; Melzack, 1968; Riesen, 1966; Schaefer, 1968b) it can be predicted that animals handled in infancy, whatever their rearing condition, ought to perform better in adulthood on avoidance tasks than animals either handled in a different stage of their development or left unhandled altogether. Furthermore, light-reared animals ought to outperform dark-reared counterparts. Thus, the pre-dictions based on the above theories would be that light-reared handled animals should outperform both light-reared nonhandled and dark-reared animals, while dark-reared handled animals should do better than dark-reared nonhandled ones. Finally, within each rearing condition, animals handled on days 1-11 should do better than animals handled postweaning and the nonhandled controls (Denenberg, 1962). METHODS Subjects The subjects (Ss) consisted of six litters of the University of B r i -tish Columbia Department of Psychology inbred laboratory strain of Long-Evans rats, ranging between 4 and 8 pups per litter. To control for littering effects, litters were split at birth. The timetable of the experi-ment allowed this approach to be utilized across rearing conditions; thus, the two litters assigned to the light-reared (LR) and dark-reared (DR) cells of handling treatment (1-11) were split littered, similarly with the two litters in the (21-32) and nonhandled (NH) conditions. Sex was disre-garded as a factor in the litter-splitting (Denenberg and Smith, 1963). The Ss were born in plastic cages, 12 by 10 by 5 inches, with saw-dust on the floor of the cage to provide nesting material for the mother and offspring. They were kept in this condition until day 11 when they were transferred by litter into large wire mesh cages in the animal care rooms. DR animals were similarly treated, except they were located in a dark-room (deprived condition) which also tended to muffle over any extrane-ous noises indigenous to an animal colony. A l l Ss were weaned on day 21 and placed in separate wire mesh cages where they were left undisturbed in the colony room (except for handling if 6 7 in a handling condition) until day 75 which marked the commencement of testing. Animals were supplied with an ad lib diet of dry food (Purina Lab Chow pellets) and water at all times. A l l efforts were made to leave the Ss untouched and undisturbed until testing. Handling Handling treatments in the present study included groups which were handled on days 1-11 and 21-32 after birth, and a nonhandled control group within each rearing condition. The actual handling procedure, similar to that used by Hunt and Otis (1963), consisted of removing the pups from the home cages and replacing each animal into another cage separate from the other littenxiates. The Ss were left in this condition for approximately three minutes and then returned to the home cage. Mothers in all groups were removed from the home cage prior to handling of the infants. This controlled for the factor of modified nursing habits produced by the remo-val of the mother, although such have proven negligible in their effect upon subsequent adult learning (Du Preez, 1964; Bronfenbrenner, 1968; Schaefer, 1968b). Furthermore, infantile exposure to different environmental temp-eratures, which has been found to affect later adult behaviour (Schaefer, 1968b), was equated across all conditions by this method of handling. O r i -ginally, it was planned to have n=8 in each cell . Unfortunately, due to 8 deaths and uncontrolled litter sizes, this was not achieved, and what resul-ted was a matrix of 6 groups with n's ranging from 4 to 8, and a total N=40, Apparatus and Training Procedure The apparatus consisted of a two-way shuttle avoidance made of ply-wood on all sides, with a grid floor consisting of rods spaced 1/2" apart through which shock could be delivered. The dimensions of the box were 24" long x 13" high x 8" wide, divided into two equal compartments by a small hurdle which also had grids to prevent perching responses. The top of the box was made of clear plexiglass through which the Ss could be observed via a mirror arrangement. The Ss were introduced into the apparatus by doors attached to either end of the box, and therefore handling was mini-mized as S could enter the box directly from the light-tight carrying cage in which he was transported to the experimental room. The two compartments of the apparatus were alike in every respect -colour was a neutral beige, and tones were presented through two Gauss Model 9000 (FT-4 Flux) speakers, positioned at the end of each compartment. Shock was delivered to the rods from two shock scramblers set at appro-ximately 85 volts. Tone was produced by a Heathkit Model 1G-82 sine wave sound generator set at 2500 cps and about 80 db. A Shunt Electric Timer (64 D . C . , supplied internally) was activated from the control panel 9 delivering the tone. Shock to either side was produced by manipulating the appropriate shocker. All testing was carried on in a dimly-lit cubicle where the experi-menter would observe S's behaviour through the mirror arrangement. Extraneous noises were muffled over by .the ventilating system so that all testing took place in a relatively quiet environment. The S was required to avoid a UCS (shock) upon the presentation of a CS (tone). CS-UCS inter-val was 5 sec. (Nakamura and Anderson, 1964; Brush, 1966). Both CS and UCS were terminated with an escape response, which consisted of the animal's jumping over the low hurdle into the other compartment. In the case of an avoidance response, CS was terminated on response and UCS was not presented. Intertrial interval was 30 sec. and 3 was punished for any responses made during the ITI. All animals were run for five sessions, 40 trials per session, and one session per day. All Ss were run for 200 trials. Animals were brought to the testing room in light-tight carrying cages and allowed a few minutes to familiarize themselves with the apparatus prior to the initial trials. No responses were counted until at least one shock (escape response) had been experienced, and S was allowed five minutes after testing to recuperate before being returned to the home cage. All testing commenced on day 75. RESULTS Avoidance Responses (AR) Presented in Table I below is the average number of avoidance responses (AR) attained by each group over 200 trials in percentage form. Analysis of variance (A NOVA) carried out on this data (Table II) indicated significance for the rearing variable (F=15.332, df=L/34, p^Looi) while there was no significance attributed to the handling variable or the inter-action term. This indicated quite clearly that rearing in differential envi-ronments significantly affects adult avoidance learning, while, contrary to many studies (Denenberg, 1968; Bronfenbrenner, 1968), handling at differen-tial periods in the infant's development had no effect. Table I Summary of Re suits on Various Measures Obtained by Experimen-tal and Control Groups Group n AR ITIR A-Scores ERL ARL (mean %) (totals) (mean %) (mean seconds) L R ( l - l l ) 8 27.8 33 23 .7 5.79 3.17 LR(21-32) 7 35.0 170 25.6 6.18 . 3.02 LR(NH) 5 33 • o 46 29.9 5.78 3.05 means 6.7 32.1 83 26.8 5.92 3.08 DR( l - l l ) 8 11.2 83 7.9 5.86 3.00 BK(21-32) 8 6.0 39 9.4 5.67 2.78 BE(MH) 4 7.7 . 20 6.7 6.33 2.77 means 6.7 8.3 47.3 6.3 (Si 2 9 2.85 10 11 Table II ANOVA's for the 5 Measures Measure Source SS df EOS F P Mean 59258.133 1 59258.133 44.556 Avoidance Rearing 20391.683 1 20391.680 15.332 .001 Responses Handling 87;176 2 43.558 0;033 NS Interaction 1423.093 2 711.545 0.535 NS Error 45218.479 34 1329.955 Mean 3688.404 1 3688.404 27.098 Rearing 353.548 1 353.548 2.597 NS r r m Handling 449.863 2 224.931 1.663 NS Interaction 1129.045 2 564.522 4.417 .05 Error 4627.812 34 136.112 Mean 39670.114 1 39670.113 33.803 Rearing 14989.136 1 14989.133 12 . 772 .001 A-Scores Handling 232.969 2 116.484 0.099 NS Interaction 280.924 2 140.462 0.120 NS Err o r 39901.339 34' ' 1173.569 Mean 1387.318 1 1387.317 8339.938 Escape Rearing 1.283 1 1.283 7.712 .01 Response Handling 1.398 2 1.395 8.389 .005 Latencies Interaction 0.478 2 0.239 1.436 NS Error 5. 656 34 0.166 Mean 309.405 1 309.406 646.602 Avoidance Rearing 1.469 1 1.469 3.070 NS Response Handling 1;027 2 0.513 . 1.064 NS Latencies Interaction 0.341 2 0.171 0.357 NS Err o r 16.269 34 0.479 12 Figure 1 presents these data graphically. Because the ANOVA il lus-trated that there was no effect of handling treatment leVels on later adult avoidance response behaviour, it is possible to collapse across groups and this gives a clearer indication of how learning went in both rearing conditions (Figure 2). Further analysis on this measure included a Duncan's Multiple Range Test (Bruning and Kintz, 1968) which essentially compares the means two at a time following a successful F-test. The test indicated that LR groups in all treatment levels performed significantly better than their dark-reared counterparts. Intertrial Interval Responses (ITIR) ANOVA carried out on the total number of ITIR per group can also be viewed in Table II, and is graphically represented in Figure 3. As the analysis indicates, there is a significant interaction effect (F=4.417, df= 2 /34, p ^ . 05), while the main effect of rearing does not quite reach signi-ficance at the .05 level (F=1.653, df=2/34, p<.10). A Pearson Product-Moment correlation coefficient was applied to the AR and the ITIR data to determine the extent to which ITI responding increased as avoidance respon-ding increased (Black and Carlson, 1959). The calculated coefficient (r= .845) was found to differ significantly from zero (t=1.917, df=18, p<. 05 one-tailed) thus indicating a significant correlation between the total number 13 of avoidance responses and the total number of intertrial interval responses by LR subjects. The curves represented in Figure 3 illustrate that the major differences occurred on days 3 and 4 of testing, and present a some-what paradoxical result in terms of the operational utility of the ITIR mea-sure. Further explanation may be found in the discussion below. A-Scores This measure is taken to be (number AR) - (number ITIR) per bloc of 40 trials (Table I) and is transformed into mean percentage form in Figure 4*. It is felt that this measure is a more accurate indicant of learning in this specific task as it reflects the animal's ability to incorporate both the facilitatory and inhibitory elements of the task, both of which ought to be severely disrupted by arousal defects (if present). A NOVA (see Table II) indicated that, as in the AR measure, the main effect of rearing was highly significant (F=12.772, df=l/34, p^.001) while the other main effect, * It can be observed in Table I that in certain cases the total number of ITIR was greater than the total number of AR. Hence, the A-Scores in such cases should be zero or negative. To permit consistency in the reporting of results, it was decided to establish a base rate for A-Scores of zero. In this way, in any bloc of 40 trials, if the animal performed more than 40 ITIR, his A-Score was set at zero. For example, in some blocks the ani-mal may have performed no avoidance responses and many intertrial inter-val responses, yet his A-Score was designated as zero. The total ITIR was included as an independent measure. 14 handling and the interaction terra did not reach significance. Therefore, it is possible to collapse across groups as Figure 4 illustrates. Duncan-s test indicated significance at the .01 level of all LR groups over DR ones. Escape Response Latency (ERL) ERL was averaged over the .40 trials per block for all subjects. ANOVA (see Table II) indicated significance on both main effects of rearing (F=7.712, df=l/34, p{.01) and handling (F=8.389, df=2/34, p<.05) with no significance on the interaction term. Figure 5 illustrates the ERL data over days, in which it can be seen that the major differences occurred on the first and second day of experimental testing. Avoidance Response Latency (ARL) A R L , like ERL above, was averaged over each block of 40 trials for each group. Due to the small number of responses in some cases, ANOVA (Table II) indicated no significant differences on any of the main effects or the interaction term. 15 FIGURE 1. Percentage correct avoidance responses (AR) over blocks of 40 trials, all groups (LR groups differentiated by closed dots. DR by open circles). 16 6 0 5 0 2 3 4 5 B L O C S FIGURE 2. Percentage correct avoidance responses collapsed across handling treatment levels, LR vs. DR. 17 2 3 4 5 BLOCS FIGURE 3. Average number of intertrial interval responses (ITIR) over blocs of 40 trials; handling treatment levels com-bined, LR vs DR. 18 6 0 5 0 4 0 2 3 4 5 BLOCS FIGURE 4. Number of A-Scores in percentage form collapsed across handling treatment levels, LR vs DR. I M U R E 5. Escape response latencies over sessions, in mean seconds. DISCUSSION T,he three handling treatments were selected on the basis of experi-ments performed by Scott (1962), Denenberg (1962), and pilot work for the present study. These studies have pointed to days 1-11 as the crucial period during which handling affects adult behaviour. Handling after this period has negligible effects, if any. Earlier pilot work for the present study indicated no difference between two groups handled on days 1-11 and 1-21 respectively so that only the 1-11 group was included*. Finally, hand-ling on days 11-21 does not seem to have any effect on later avoidance learning so this group was not included in the present study (Denenberg and Karas, 1961). The procedures and rearing conditions were designed to isolate a treatment in infantile development which would significantly affect adult behaviour. Specifically, it was hypothesized that excessive emotionality or hyperarousal would occur as a result of deficiencies in arousal control * The pilot study also indicated some rather puzzling results. Although the effects of handling on later avoidance learning agreed with other studies (see Denenberg, 1968), dark-reared animals were found to perform signi-ficantly better than light-reared ones. This discrepant finding can be ex-plained to some extent by the fact that the "n" of each group was very small, that animals were trained only a total of 100 trials (25 per day), and inter-trial interval responses were not recorded. Conceivably, therefore, in terms of the A-Score, such results may have indeed masked quite opposite tenden-cies. The fact that the handling variable was significant in both rearing conditions allowed the above handling periods to be chosen. 20 21 brought on by restricted infantile development (Melzack, 1968) thus dis-rupting normal integrative patterns of response (Riesen, 1966). The data indicated that visual deprivation produced an unmistakeable deficit in the learning of avoidance behaviour by adult rats. This deficiency in the two-way shuttle avoidance is illustrated by the fact that all LR groups, whether handled or not, performed significantly more AR and A-Scores than DR groups, and escaped significantly faster from an aversive situation, especially in the initial days of testing. Furthermore, contrary to an extensive literature (Denenberg, 1968; Schaefer, 1968b; Thompson and Schaefer j 1961), handling at various stages of an animal's early life had no appreciable effect on later avoidance learning. This last finding is difficult to reconcile with the theoretical assump-tions and experimental findings of Denenberg and his group (Denenberg and Karas, 1960, 1961; Denenberg and Haltmeyer, 1967; Bell and Denenberg, 1963). Denenberg, Morton, Kline and Grota (1962) found that increased duration of handling in infancy decreased adult emotional responsiveness only so long as the handling period included Denenberg's "critical period" for this effect (Denenberg, 1962; Denenberg and Kline, 1964). In light of the above analysis, the groups handled on days 1-11 ought to have performed significantly better than later handled and nonhandled groups. This was not the case in the present study. 22 This finding may be explained by the fact that the present study differed in a number of ways from other handling studies in which significant effects were obtained. There are few studies in which the two-way shuttle avoidance apparatus was used to test for the effects of infantile handling. Denenberg and his group, for example, have used one-way avoidance chambers and open-field tasks to measure emotionality (Denenberg, 1966) as has Scaefer (1968b). Secondly, nonhandled animals in both rearing conditions may have acquired more stimulation than animals in previous studies. In other studies, the rat pups were left with the mother in the nesting cage until weaning (Schaefer, 1968a, 1968b) while in the present study the animals were transferred to wire mesh group cages on day 11. This novel environment may have provided extra stimulation for the nonhandled groups which could have counteracted any effects due to handling. However, it can be seen that among light-reared animals, the nonhandled group does better (though not significantly) than the 1-11 group (see Table II). Considering the fact that both groups were removed to wire mesh cages at the same time, it seems hardly likely that the above criticism can account for the data. On the other hand, NH animals in the present study would be exposed to different temperatures during the handling procedure, as indeed were all the subjects (Schaefer, 1968b). Taking the data of Schaefer into account, this temperature change may have induced the reactions necessary to appro-ximate the handling condition. More research would have to be carried out 23 to determine if such were the case in the present study. Finally, the conditions in the colony room itself may have played a crucial role in the present study. Because there is quite a lot of activity in the colony room during the course of a normal day, it might be postulated that NH rats received a significant amount of "supranormal" stimulation which may have resulted in increased learning ability in adulthood. McMich-ael (1966) found that handled and nonhandled rats did not differ in a drinking test for emotionality if they were raised in the usual colony rooms as des-cribed above. He did obtain differences, however, if the rats were housed in a more secluded area where the daily noises, sights, and smells of the colony room were non-existent. As McMichael (1966, p.436) stated: " . . . the effect of a specific infant treatment is a complicated function of rearing and maintenance conditions, mode of response measured, and the sequence of stresses involved in later testing". Denenberg, Schell, Karas and Haltmeyer (1966) raised rats both in the noisier colony room commonly used for raising and housing experimental animals, and also in a quieter, more secluded room where the Ss were at-tended to by the e xperimenter alone. Half of each group was handled in infancy. These workers hypothesized that if ambient environmental st i-mulation were functionally similar to handling, then NH groups raised in the "normal" colony room ought to perform similarly to handled animals 23 on an open-field test when adult. Such was not the case in their study. These two rather discrepant findings are noteworthy for they illust-rate the importance of the response being measured. While colony condi-tions masked the effects of handling on a drinking test for emotionality (McMichael, 1966), differences were perceived on an open-field test suppo-sedly measuring the same underlying variable (Denenberg, Schell, Karas and Haltmeyer, 1966). In both these studies, animals were not raised in a visually deprived environment as were those in the present study, nor did they use avoidance responding as the critical measure. It is obvious that more research wil l have to be carried out to elucidate the effects of colony conditions on later adult avoidance responding. Another possible explanation of the results found in the present study is the finding of Harrington and Kohler (1966). They taught rats to press a lever for mild shock reinforcement and found that deprived animals learned this response significantly faster than nondeprived ones. They interpreted this finding according to an "optimum arousal" hypothesis which states that any stimulus can act as a positive reinforcer at appropriate intensity levels though it may be an aversive stimulus at higher levels. They felt that "the stimulus proved relatively more attractive to the animals with relatively less sensory experience" (Harrington and Kohler, 1966, p. 807). One could therefore interpret the present findings from this position, which would state 24 that the DE animals did more poorly than the LR ones because they appre-ciated the aversive UCS (shock) more. This kind of approach raises some intriguing questions, such as what is the crossover point on any stimulus dimension which converts it from a positive to a negative stimulus. It is possible to determine such a crossover point by simply varying the dimen-sion of shock presented to the animals, and observing any change in escape behaviour (ERL) and avoidance behaviour (A-Scores). In the present study, however, there was no difference in performance between handled and nonhand-led groups, and it would follow logically from the position of Harrington and Kohler (1966) that handled groups, because they have relatively more sensory experience, should outperform nonhandled animals. A much more reasonable and parsimonious theory in terms of the present data is that of Melzack (1968). According to his position, animals reared in restricted environments do not possess the necessary prior expe-riences upon which appropriate adult behaviour is based. Because cell assemblies (Hebb, 1949) are lacking, the animal's selective attentional mechanisms have no basis upon which to compare incoming stimuli. Thus, filtering or centrifugal mechanisms do not screen out irrelevant information which, together with normal input, bombard the central nervous system, and especially the reticular formation (Melzack and Burns, 1965). This model, then, "describes a vicious circle in which failure to filter out i r re -25 levant information (on the basis of prior experiences) leads to excessive arousal, which in turn interferes with mechanisms, both innate and acquired, that would normally act in the selection of cues for adaptive response" (Mel-zack, 1968, p. 11). If one accepts the assumption that two-way shuttle avoi-dance learning with shock contingencies can be arousal-producing, then Melzack*s hypothesis accounts quite adequately for the effects of differential rearing on adult behaviour. However, if his theory is extended to include the effects of handling, it might predict that handled Ss should outperform nonhandled ones. This was not the case in the present study. If indeed Melzack1 s theory would lead to such a prediction, it is in need of modifica-tion. Dark-reared animals are deprived of the visual cues so essential to the formation of stable acquisitive functioning and there are numerous physiological concomitants to emphasize the point (Bennett, Diamond, Krech and Rosenzweig, 1964; Riesen, 1966; Valverde, 1967). Furthermore, dark-rearing, at least in the present study, filtered out much of the auditory stimulation normally encountered in a laboratory situation. It is interesting to speculate on the relevant anatomical substrates which are affected. For example, certain areas of the inferotemporal cortex (A-IV) are composed of cells which respond actively to both visual and auditory information (Des-medt, 1960). It is also known that there are extensive connections between 26 this area and certain regions of the reticular formation which is thought to underlie the arousal properties of normal behaviour (Lindsley. 1961). Taking into account the anatomical evidence and Melzack's theorizing, it might be fruitful to survey these relevant areas more closely (by cell count, for example) in an attempt to uncover the physiological deficiencies in the DR animals which are associated with the behavioural deficits; One of the most revealing pieces of information uncovered by the pre-sent study is the relation of ITIR rate to learning of the task. Thompson, Sachson and Higgins (1969) analysed the intertrial response rate (ITIR) of animals in a two-way shuttle avoidance apparatus in an attempt to determine the relationship between ITIR rate and learning. As they point out, ITER rate has been observed to increase (Black and Carlson, 1959), decrease (Murphy and Miller, 1958), remain constant (Mowrer and Lamoreaux, 1942), or first decrease and then increase (Black and Annau, 1S63) over shuttle avoidance learning. Thompson, Sachson and Higgins demonstrated that ITIR rate varies systematically over the course of avoidance conditioning. Early freezing associated with novel exposure to the CS-UCS situation reflects a low rate of spontaneous barrier crossings. Furthermore, it has been shown that both spontaneous barrier crossings prior to avoidance training and movement during the CS in early conditioning are highly correlated with subsequent performance in a positive fashion (Weiss, Krieckhaus and 27 Conte, 1968). Interestingly, these workers also demonstrated that the probability of correct avoidance responding could be reliably predicted from movement during the CS. Finally, Thompson, Sachson and Higgins (1969) stated: "Assuming that ITIR's and movement during the CS reflect some general activity level, it follows that animals with high ITIR rates should learn more rapidly than animals with low ITER rates" (p. 565). Though the correlation between total AR and total ITIR over all trials for light-reared Ss was significant, this is not sufficient evidence to conclude that there is some crucial relationship between ITI activity and avoidance responding in the present study. Specifically, it might be hypothesized that the peak of the LR curve in Figure 3 could be utilized as a learning crossover point; that is, as the animal learns the proper nature of the response - both to jump at the CS and not to jump during the ITI - the number of ITIR's ought to first increase, then decrease as learning proceeds. This situation should parallel the avoidance response curve in Figure 2; that is, many more ITIR's should be committed as the animal first begins to associate a jumping response with the CS, only to drop off as the animal makes a discriminated response to the CS alone. However, it can be seen in Figure 3 that the greatest num-ber of ITIR's occurred on days 3 and 4, while the greatest increase in AR occurred on day 2 (see Figure 2). This indicates that, in terms of the present study, it is not possible to use the ITIR curve peak as a hypothetical learning 28 crossover point. One can interpret the failure of the dark-reared animals to learn the avoidance response from the viewpoint that they did not learn to discriminate a CS from a non-CS condition (Anderson, 1969; Herrnstein, 1969). This does not account, however, for their total lack of performance, independent of CS contingencies. The task itself was difficult in that there were two conflicting components involved: (i) the animal had to learn to jump into a compartment at the sound of a CS, a compartment which was associated with fearful cues in that the animal was inevitably shocked there at least a number of times; and (ii) S had to learn not to jump until the CS had oc-curred. That arousal was a factor can be noted from the finding that hyperar-oused animals tend to misjudge a temporal task (Falk and Bindra, 1954, cited in Milner, 1970) and thus to perform the task prior to a designated signal. This was clearly seen in the case of the light-reared animals. As for the dark-reared animals, one can only assume that they were in such a state of hyperarousal that nearly al l responding was inhibited (Hebb, 1966; Melzack and Thompson, 1956; Wahlsten and Sharp, 1969). This latter statement is further strengthened fry the fact that dark-reared animals escaped significantly more slowly in the initial two days of training when the novelty of the situation can be presumed to have its greatest effect. The one feature of the experiment which is difficult to interpret in 29 light of recent evidence is the generally low rate of responding for all Ss. There are a number of factors which can account for this discrepancy. Age has been found to affect avoidance behaviour (Klein and Spear, 1969) and, as Ss were run at 75 days of age in the present study, it might be valuable to repeat certain aspects of the experiment with both older and younger animals. Another important consideration is the type of apparatus used and the task required of the animal. In the present study, a two-way shuttle avoidance box utilizing one CS (tone) was used. Other studies have used multiple cues (Levine, Chevalier and Korchin, 1956), one-way avoidance chambers (Denenberg, 1962), and automated chambers where the response required was different from locomoting between two chambers (Baum, 1969). Also, various training procedures have been attempted, from giving the Ss five trials per day (Denenberg, 1962) to the full 200 trials in one session (Thompson, Sachson, and Higgins, 1969). Criteria to acquisition have ranged from ten correct avoidance responses (Thompson, Sachson and Higgins, 1969) to three in a row (Coulter, Riccio and Page, 1969), to a percentage or raw total out of the entire testing period, which itself can range from 40 to 200 trials (Denenberg, 1968). A l l of these factors, including levels and types of CS and UCS, can be assumed to affect the learning in some way. Finally, so many different tasks have been used (Bolles, 1969) that for this, and the reasons enumerated above, one must be cautious in drawing genera-SUMMARY Groups of rats were either handled on days 1-11 or 21-32, or left non-handled. Half of the Ss in each of these handling conditions were raised in a darkroom (deprived environment), half were raised in the normal colony. On day 75, al l rats were run on a modified two-way shuttle avoidance task. The CS was a 2500 cps pure tone, UCS was scrambled foot shock, and CS-UCS interval was 5 sec. Intertrial interval responses (ITIR) were punished. The ITI itself was 30 sec. A l l animals were run on one session a day, 40 trials per session, for a total of 200 trials. The five measures taken included percentage correct avoidance responses, intertrial interval responses, A -Scores (number correct avoidance responses-ITIR), and escape and avoid-ance response latencies. Handling had no effect on any of the measures except the escape response latency, while rearing in differential environments produced significant results with light-reared animals outperforming dark-reared counterparts on percentage avoidance, early ITI responding, A-Scores, and escape response latencies. A number of theories were discussed in relation to the above findings. It was felt that the present study provided negative evidence for the theory of Denenberg (1962) and Schaefer (1968a, 1968b), while it seemed that Melzack's (1965, 1968) formulations could best account for the data. A number of questions raised by the findings of Harrington and Kohler (1966) 31 32 were discussed. It was concluded that rearing animals in a deprived environ-ment results in an inability to appropriately integrate response patterns due to arousal control difficulties. Hence performance was inferior on the task used in the present study by animals reared in deprived environments. REFERENCES Ader, R. Effects of early experience and differential housing on behaviour and susceptibility to gastric erosions in the rat. Journal of Compa- rative and Physiological Psychology, 1965, 60, 233-238. Anderson, N.H. Variation of CS-UCS interval in long-term avoidance con-ditioning in the rat with wheel-turn and with shuttle tasks. Journal  of Comparative and Physiological Psychology, 1969, 68, 100-106. Baum, M . Extinction of an avoidance response following response prevention: some parametric investigations. Canadian Journal of Psychology, 1969, 23, 1-10. Bell, R.W. and Denenberg, V.H. The interrelationships of shock and critical periods in infancy as they affect adult learning and activity. Animal  Behaviour, 1963, 11, 21-27. Bennett, E.L., Diamond, M.C., Krech, D. and Rosenzweig, M.R. Chemi-cal and anatomical plasticity of brain. Science, 1964, 146, 610-619. . Black, A.H. and Annau, Z. Time-out responding during avoidance condition-ing and extinction in the rat. Canadian Journal of Psychology, 1963, 17, 165-173. Bolles, R. C. Avoidance and escape learning: simultaneous acquisition of different responses. Journal of Comparative and Physiological  Psychology, 1969, 68, 355-358. Bronfenbrenner, U. Early deprivation in mammals and man. In Newton, G. and Levine, S. (Eds.): Early Experience and Behaviour. Spring-field, Illinois: C.C. Thomas, Publishers, 1968. Bruning, J. L. and Kintz, B. L. Computational handbook of statistics. Palo Alto: Scott, Foresman and Company. Brush, F.R. On the differences between subjects that learn and do not learn to avoid shock. Psychonomic Science, 1966, 5_, 123-124. Coulter, X., Riccio, D.C. and Page, H.A. Effects of blocking an instru-33 34 mental avoidance response: facilitated extinction but persistence of "fear". Journal of Comparative and Physiological Psychology, 19S9, 68, 377-381. Denenberg, V.H. An attempt to isolate critical periods of development in the rat. Journal of Comparative and Physiological Psychology, 1962, 55, 813-815. Denenberg, V. H. A consideration of the usefulness of the critical period hypothesis as applied to the stimulation of rodents in infancy. In Newton, G. and Levine, S. (Eds.): Early Experience and Behaviour. Springfield, Illinois: C.C. Thomas, Publishers, 1968. Denenberg, V.H. and Bell, R.W. Critical periods for the effects of infantile experience on adult learning. Science, 1960, 131, 227-228. Denenberg, V.H. and Haltmeyer, G.C. Test of the monotonicity hypothesis concerning infantile stimulation and emotional reactivity. Journal of  Comparative and Physiological Psychology, 1967, 63, 394-396. Denenberg, V.H. and Karas, G.G. Interactive effects of age and duration of infantile experience on adult learning. Psychological Reports, 19®0, 7, 313-322. Denenberg, V.H. and Karas, G.G. Interactive effects of infantile and adult experiences upon weight gain and mortality in the rat. Journal of  Comparative and Physiological Psychology, 1961, 54, 685-689. Denenberg, V.H. and Kline, N.J. Stimulus intensity versus critical periods: a test of two hypothesis concerning infantile stimulation. Canadian  Journal of Psychology, 1964, 18, 1-5. Denenberg, V.H. and Smith, S.A. Effects of infantile stimulation and age upon behaviour. Journal of Comparative and Physiological Psycho- logy, 1963, 56, 307-312. Denenberg, V.H. and Whimbey, A.E. Infantile stimulation and animal hus-bandry: a methodological study. Journal of Comparative and Physio-logical Psychology, 1963, 56, 312-315. Denenberg, V.H., Morton, J.R.C, Kline, N.J. and Haltmeyer, G.C. Com-35 parisons of background stimulation and handling as forms of infan-tile stimulation. Psychological Reports, 1966, 19, 943-948. Desmedt, J . E . Neurophysiological mechanisms controlling acoustic input. In Rasmussen, G . L . and Windle, W . F . (Eds.): Neural mechanisms  of the auditory and vestibular systems. Springfield, Illinois: C . C . Thomas, Publishers, 1960. Du Preez, P . D . The persistence of some effects of handling in infancy on the behaviour of the adult rat. Quarterly Journal of Experimental  Psychology, 1964, 16, 147-155. Ferguson, G . A . Statistical analysis in psychology and education (2nd Edi - tion). New York: McGraw-Hill, 1966. Freud, S. A general introduction to psychoanalysis. New York: Washington Square Press, 1965. Harrington, G . M . and Kohler, G.R. Sensory deprivation and sensory rein-forcement with shock. Psychological Reports, 1966, 18, 803-808. Hebb, D.O. The organization of behaviour. New York: Wiley, 1949. Hebb, D . O . ' A textbook of psychology (2nd Edition). New York: Wiley, 1966. Hebb, D.O. Drives and the c.n.s, (conceptual nervous system). Psycho-logical Review, 1955, 62, 243-254. Herrnstein, R . J . Method and theory in the study of avoidance. Psychologi- cal Review. 1969, 76, 49-69. Hess, E . H . Imprinting. Science, 1959, 130, 133-141. Hunt, H . F . and Otis, L .S . Early "experience" and its effects on later beha-vioural processes in rats: I. initial experiments. Transactions of  the New York Academy of Sciences, 1963, 25, 858-870. King, J . A . Parameters relevant to determining the effects of early experience upon the adult behaviour of animals. , Psychological Bulletin, 1958, 55-, 46-58. Klein, S. B. and Spear, N . E . Influence of age on short-term retention of 36 active avoidance learning in rats. Journal of Comparative and  Physiological Psychology, 1969, '68, 583-589. Levine, S. and Wetzel, A . Infantile experiences, strain differences, and avoidance learning. Journal of Comparative and Physiological  Psychology, 1963, 56, 879-881. Levine, S., Chevalier, J . A . and K or chin, S.J . The effects of shock and handling In infancy on later avoidance learning. Journal of Persona-lity, 1956, 24, 475-493. Lindsley, D . B . The reticular activating system and perceptual integration. In Sheer, D . E . (Ed.): Electrical stimulation of the brain. Austin: University of Texas Press, 1961. Melzack, R. Effects of early experience on behaviour: experimental and conceptual considerations. In Hoch, P . H . and Zubin, J . (Eds.): Disorders of perception. New York: Grune and Stratton, 1965. Melzack, R. Early experience: a neuropsychological approach to heredity environment interactions. In Newton, G. and Levine, S. (Eds.): Early experience and behaviour. Springfield: C . C . Thomas, 1968. Melzack, R. and Burns, S.K. Neurophysiological effects of early sensory restriction. Experimental Neurology, 1965, 13, 163-175. Melzack, R. and Thompson, W.R. Effects of early experience on social behaviour. Canadian Journal of Psychology, 1956, 10, 82-90. Milner, P. Physiological psychology. New York: Holt, Rinehart and Winston, 1970. Mowrer, O . H . and Lamoreaux, R .R . Avoidance conditioning and signal duration - a study of secondary motivation and reward. Psychologi- cal Monographs, 1942, 54 (5, Whole #247). Murphy, J . V . and Miller, R . E . The effect of intertrial responding on condi-tioning and extinction of avoidance behaviour. Journal of Experimental  Psychology, 1958, 56, 256-261. 37 McMichael, R.E. Early experience effects as a function of infant treatment and other experiential conditions. Journal of Comparative and Physio- logical Psychology, 1966, 62 , 433-436. Nakamura, C.Y. and Anderson, N.H. Avoidance conditioning in wheelbox and shuttle box. Psychological Reports, 1964, 14 , 327-334. Riesen, A.H. Stimulation as a requirement for growth and function. In Fiske, D.W. and Maddi, S.R. (Eds.): Functions of varied experience. Homewood, Illinois: Dorsey Press, 1961. Riesen, A.H. Sensory deprivation. In Stellar, E. and Sprague, J. (Eds.): Progress in physiological psychology, volume I. New York: Aca-demic Press, 1966. Schaefer, T. Early "experience" and its effects on later behavioural processes in rats: II. a critical factor. Transactions of the New York Academy  of Sciences, 1963, 25, 871-889. Schaefer, T. Infantile handling and body temperature change in the rat. I. Initial investigations of the temperature hypothesis. Transac-tions of the New York Academy of Sciences, 1968a, Series 11, 30, 977-984. Schaefer, T. Some methodological implications of the research on "early handling" in the rat. In Newton, G. and Levine, S. (Eds.): Early  experience and behaviour. Springfield: C.C. Thomas, 19633. Scherrer, J. and Fourment, A. Electrocortical effects of sensory depri-vation during development. Progress in Brain Research,1964, 9, 103-112. Scott, J. P. Critical periods in behavioural development. Science, 1962, 138, 949-958. Small, W.S. Notes on the psychic development of the young rat. American  Journal of Psychology, 1899, 11, 80-100. Tees, R. C. Effect of early visual restriction on later visual intensity dis-crimination in rats. Journal of Comparative and Physiological  Psychology, 1968, 66, 224-227. 38 Tees, R . C . Effect of early visual restriction on subsequent activity and emotionality in the rat. Journal of Genetic Psychology, 1969, 114, 193-202. Thompson, C. P . , Sachson, S. M . and Higgins, R. C. Distribution of inter-trial responses in shuttle-box avoidance conditioning. Journal of  Comparative and Physiological Psychology, 1969, 69, 563-572, Valverde, F . Apical dendritic spines of the visual cortex and light depriva-tion in the mouse. Experimental Brain Research, 1967, 3, 337-352. Wahlsten, D. and Sharp, D. Improvement of shuttle avoidance by handling during the intertrial interval. Journal of Comparative and Physiolo-gical Psychology, 1969, 68, 252-259. Weiss, J . M . , Krieckhaus, E . E . and Conte, R. Effects of fear conditioning on subsequent avoidance behaviour and movement. Journal of Compa- rative and Physiological Psychology, 1968, 65, 413-421. Winer, B . J . Statistical principles in experimental design. New York: McGraw-Hill, 1962. 


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