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Preweaning handling and shock : their relationship to subsequent adult emotionality and discrimination… Toussaint, Nelly Adelina 1969

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PREWEANING HANDLING AND SHOCK: THEIR RELATIONSHIP TO SUBSEQUENT ADULT EMOTIONALITY AND DISCRIMINATION LEARNING by N. A. TOUSSAINT B.A., University of Tulsa, 1968 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS in the Department of Psychology We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA December, 1969 In presenting t h i s t h e s i s in p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree that the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study. I f u r t h e r agree tha permission for extensive copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the Head of my Department or by h i s r e p r e s e n t a t i v e s . I t i s understood that copying or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l gain s h a l l not be allowed without my w r i t t e n permission. Department of ?Sy<U+QAO <jT / The U n i v e r s i t y of B r i t i s h Columbia Vancouver 8, Canada Date ABSTRACT Three groups of nine male hooded rats each were either daily shocked, daily handled, or l e f t undisturbed from three to 22 days of age. When 67 days old, a l l S_s were administered a series of emotionality tests followed by five days of training i n a brightness discrimination task which required a minimum of locomotion. This was followed by a drinking suppression test based on a conditioned fear measuring procedure designed by Leaf and Muller (1965). The shocked rats showed less emotionality and superior learning than the handled and nonhandled rats. The drinking suppression test failed to distinguish between the groups although there was a significant conditioning effect. A correlation of a l l the dependent measures indicated that differences in locomotor activity might have been reflected in the learning scores. It was concluded that infantile handling and shock affected adult emotionality and learning differently, and that neither manipulation produced unitary effects on the emotionality meaaures. i i TABLE OF CONTENTS Page Abstract • i Introduction . . . . 1 Method 8 Q Subjects • •> • • • ' g Apparatus ; • Procedure . . . H Results . . i 16 35 Discussion . . . . . . . 43 References i i i LIST OF TABLES Page Table 1 Transformed (log e) Means and Standard Deviations of the Latencies of Firs t Emergence . . . 17 Table 2 Summary of Analysis of Variance of Latencies of F i r s t Emergence 17 Table 3 Transformed (log e) Means and Standard Deviations of the Latencies of Fi r s t Cross 18 Table 4 Summary of Analysis of Variance of Latencies of F i r s t Cross 18 Table 5 Means and Standard Deviations of the Number of Crosses . . . . . . 19 Table 6 Summary of Analysis of Variance of the Number of Crosses 19 Table 7 Transformed (log e) Means and Standard Deviations of the Time Spent in Home Cage 21 Table 8 Summary of Analysis of Variance of Time Spent in Home Cage 21 Table 9 Transformed (log e) Means and Standard Deviations of the Latencies of Entrance to Discrimination Chamber 22 Table 10 Summary of Analysis of Variance of Latencies of Entrance to Discrimination Chamber 22 Table 11 Means and Standard Deviations of the Time i n Min. Taken to Make Firs t 20 Choices 24 Table 12 Summary of Analysis of Variance of Latencies of Time Taken to Make First 20 Choices 24 Table 13 Means and Standard Deviations of the Suppression Ratios During the Pre- and Post-conditioning Drinking Tests 26 Table 14 Summary of Analysis of Variance of Suppression Ratios During the Pre- and Post-conditioning Drinking Tests 26 Table 15 Means and Standard Deviations of the Number of Correct Choices in the Discrimination Task 27 iv Page T a b l e 16 S u m m a r y o f A n a l y s i s o f V a r i a n c e o f t h e N u m b e r o f C o r r e c t C h o i c e s . . . . . . . . . 27 T a b l e 17 S i m p l e M a i n E f f e c t s A n a l y s i s o f V a r i a n c e o f t h e M e a n N u m b e r o f C o r r e c t C h o i c e s o v e r t h e S i x t h T r a i n i n g S e s s i o n s . . . 29 T a b l e 18 C o r r e l a t i o n M a t r i x o f t h e D e p e n d e n t V a r i a b l e s . . 31 T a b l e 19 C o r r e l a t i o n M a t r i x o f t h e T i m e D e p e n d e n t V a r i a b l e s 3 2 2 T a b l e 2 0 C o r r e l a t i o n C o e f f i c i e n t s a n d r b e t w e e n L e a r n i n g a n d E m o t i o n a l i t y S c o r e s . . . . 3 4 LIST OF FIGURES Figure 1 Apparatus used for discrimination training and latency of emergence tests Page Figure 2 Transformed (log e) latencies of f i r s t , emergence, f i r s t cross, and entrance into the discrimination chamber . . . . 23 Figure 3 Mean number of correct choices in the discrimination task as a function of training day for the Handled (H), Shocked (s), and Nbnhandled (NH) groups . . . 28 v i ACKNOWLEDGEMENT The writer would like to express her gratitude to those individuals whose cooperation made i t possible to accomplish this study. In particular, thanks are due to Dr. Roderick Wong and Dr. George A. Raymond who provided constructive criticism of the design and writing of the study and valuable technical assistance; and to Godfried, my husband, who provided the expert drawing of figures and a great deal of encouragement. 1 Handling and shock, administered to the rat during the f i r s t twenty days of l i f e , have been found to markedly change i t s adolescent and adult psychological and physiological functioning. When compared with each other and with a nonmanipulated control group, these two i n f a n t i l e t r e a t -ments have been found to produce d i f f e r e n t behavioral as we l l as psycho-l o g i c a l effects (Ader, Friedman, Grota, and Shaffer, 1968; Levine, Haltmeyer, Karas, and Denenberg, 1967; Ader, 1968; Ader and Friedman, 1965; Henderson, 1967, 1968; Goldman, 1965; Denenberg and Kl i n e , 1964; Salama and Hunt, 1964; Denenberg and Smith, 1963; Levine, Chevalier, and Korchin, 1956). However, whether the differences between the effects of the two treatments are quantitative or q u a l i t a t i v e s t i l l remains to be determined. For instance, several studies indicate that preweaning handling reduces emotionality while preweaning shock i s less e f f e c t i v e (Ader, 1965; Goldman, 1965; Denenberg and Smith, 1963; Denenberg, Carlson, and Stephens, 1962; Levine, 1957, 1958). Yet, other studies report opposite findings (Henderson, 1967, 1968; Ader, 1966; McMichael, 1966; Denenberg and Kl i n e , 1964). The lack of uniformity i n the findings may be the r e s u l t of the great variety of (1) procedures, (2) parameters of the independent variables (e.g. days of handling, i n t e n s i t y and frequency of shock, e t c . ) , and/or (3) the test situations used i n the various experi-ments. The d i v e r s i t y of results may also be due to the apparently sensitive nature of the effects of i n f a n t i l e treatments which seem to interact i n a complex manner with an assortment of variables whose effects have not yet been parametrically investigated (Henderson, 1968). Despite the d i s -crepancies i n the findings, the fact that does emerge i s that d i f f e r e n t i a l effects are produced by preweaning handling and shock. Preweaning Manipulation and Learning An important but less explored aspect of the effects of early manipulation on subsequent behavior concerns the effects of Infantile handling and shock on subsequent learning capacity i n adulthood. The questions of whether handling and shock affect learning a b i l i t y differently and of whether the effects on learning are independent of or interactive with the effects of emotionality have not been adequately examined. For example, one of the learning situations most commonly used i s avoidance learning. The results from the various experiments that have used this test are not completely comparable with each other; nevertheless, they have generally indicated that handled and shocked rats show superior learning than control controls and that the shocked rats tend to learn faster than the handled ones (Denenberg and Smith, 1963; Denenberg and Kline, 1964; DuPreez, 1963; Ader, 1968; Levine, Chevalier, and Korchin, 1956). Contradictory evidence i s also available (Goldman, 1965; Ader, 1965; Henderson, 1968). The avoidance test, however, does not specifically tap learning a b i l i t y as such since emotionality factors trand to be also reflected in i t s results. The situation involves a stressor, shock, that evokes emotional responses such as freezing and crouching which tend to interfere with the locomotor responses required in the learning task. Consequently, i t is not possible to conclude on the basis of the outcomes of the avoidance learning task that manipulated rats are better learners than nonmanipulated ones because of the con-tamination of the learning measure with emotionality factors. Denenberg and Morton (1962) used the Hebb-Williams problem-solving maze assuming this task to be a less stressful learning situation. They 3 found that food deprived handled and nonhandled animals did not differ from each other in the number of errors made in reaching the goal for food reward. Such a finding led them to conclude that, "preweaning stimulation such as shock and handling affect emotional processes but do not have any direct effect upon perceptual or problem solving behavior." (Denenberg and Morton, 1962, p. 1098). Such a sweeping generalization has not been subsequently followed by further investigations employing the same test. Moreover, replication of this experiment using preweaned shocked subjects has not been done. Therefore, in the absence of supporting data, this conclusion can be considered as somewhat of an overgeneralization. Perhaps a more serious criticism of Denenberg and Morton's (1962) conclusion is that the procedure followed in their study does not seem to present adequate conditions for a test of learning abilities. The pro-cedure involved 11 pretesting sessions of eight trials each during which the rats were exposed to the various problems on which they were subsequently tested. Hence, such an extended pretesting could have eliminated any learning capacity differences which might have existed between the groups. Several findings suggest that differences in emotionality between manipulated and unmanipulated rats tend to diminish the more they are exposed to a variety of situations (DuPreez, 1963; McMichael, 1961; Ader, 1959). An analogous trend could be suggested for the learning differences when these are measured in the Hebb-Williams maze. Simple instrumental learning tasks involving food reward have been also used to assess learning capacities, e.g. the straight runway (Spence and Maher, 1962; Goldman, 1965), the elevated T maze (DuPreez, 1963), and the enclosed T maze (Wong and Jamieson, 1968). The studies by Spence and 4 Maher (1962) and by DuPreez (1963) did not find a s i g n i f i c a n t f a c i l i t a t i o n i n learning due to i n f a n t i l e handling and shock. Goldman's (1965) study, on the other hand, did y i e l d a s i g n i f i c a n t difference i n learning attributed to i n f a n t i l e handling and shock. Wong and Jamieson (1968) were able to account for the discrepancies among these three studies i n terms of t h e i r v a r i a t i o n i n postweaning housing. Whereas Spence and Maher (1962) and DuPreez (1963) housed their animals i n groups, Goldman's (1965) animals were housed i n d i v i d u a l l y . Group postweaning housing has been shown to decrease or eliminate differences between animals d i f f e r e n t l y manipulated during early l i f e (Ader, 1965). In order to test i f housing was the s i g n i -f i c a n t variable, Wong and Jamieson (1968), a f t e r adopting a procedure of ind i v i d u a l postweaning housing, compared the running speeds of handled and nonhandled rats i n a brightness discrimination and reversal task. The manipulated rats ran s i g n i f i c a n t l y faster than the control group. Although Wong and Jamieson*s (1968) and Goldman's (1965) studies yielded superior learning scores by the manipulated groups, neither of them can be considered as the c r u c i a l experiment i n which differences i n associative capacity as a function of early manipulation were demonstrated. The weakness In Goldman's res u l t s was evidenced by the fact that differences between the groups i n the instrumental task were dependent on sex and on whether or not the rats had been previously shocked on the testing runway. Wong and Jamieson's data, on the other hand, even though i t showed strong and consistent differences i n the running speeds, showed no s i g n i f i c a n t differences i n the learning measure expressed by the percentage of correct choices. The groups d i f f e r e d s i g n i f i c a n t l y on t h i s measure only on the l a s t two days of the 20 days of acquisi t i o n . 5 Aside from the criticisms specific to the particular experiments, there s t i l l remains a very important question regarding the vali d i t y of the running speed as a comparative measure of learning among manipulated ' and unmanipulated rats. Handled, shocked, and unmanipulated rats have been found to diff e r i n their degree of exploratory behavior. Differ-ences i n exploratory behavior have been found particularly when such behavior has been measured i n short spans of time by the activity measure in the open f i e l d or by the latency-of-emergence tests (Goldman, 1965; Salama and Hunt, 1964; DuPreez, 1963; Ader, 1965; Henderson, 1966; DeNelsky and Denenberg, 1967). On the assumption that exploratory and running behavior are both dependent on locomotor activity, an aspect on which highly reactive animals are more l i k e l y to be impaired, i t could be expected that running speed, just as latency and activity measures, is again reflecting differences in emotionality rather than differences in learning. In a situation closely resembling a straight runway but i n which there was no reward involved,Meyers (1962) found that over a period of five days manipulated rats showed significantly shorter latencies of emergence and more entries into the runway than the nonmanipulated rats. Based on the similarities of the situations, i t could be suggested that since differences in activity in the runway are already present when no appetitive factor i s involved, such differences could show up when there is a reward involved. The primary purpose of the present study was to compare the learning performance of preweaned shocked and preweaned handled rats with the performance of nonmanipulated rats i n an instrumental learning situation involving positive reinforcement. The requirements of the task were such 6 that i t was expected that several of the usually confounded factors would be reduced, p a r t i c u l a r l y differences i n exploratory behavior. The learning task concerned brightness discrimination. I t was carried out i n a chamber of such dimensions and characteristics that the necessary locomotor a c t i v i t y required to obtain the reward would be minimized. Preweaning Manipulation and Suppression of Drinking A second purpose of the study was to use a conditioned fear measuring procedure designed by Leaf and Muller (1965) to determine i f such a technique could be used to distinguish among the dif f e r e n t emotionality levels of the handled, shocked, and unmanipulated groups. The most t y p i c a l l y used measure of conditioned fear i s the amount of suppression of some ongoing operant behavior during the presence of a signal which has been previously associated with shock (Estes and Skinner, 1941). Leaf and Muller's technique i s based on the same p r i n c i p l e ; however, i t i s a shorter and simpler technique and presented a t t r a c t i v e p o s s i b i l i t i e s for measuring emotionality mainly because i t i s based on the suppression of consummatory response, drinking. Consummatory baselines are r e l a t i v e l y easy to establish since they are based on responses forming a large part of the animals' natural repertoire of behavior, and are consequently more rea d i l y emitted than other operant responses. I t was thought that the degree of suppression of a response with high pro b a b i l i t y of occurrence would be a sensitive indicator of the degree of emotionality evoked by a previously fear-conditioned s i g n a l . The decision to use t h i s conditioned fear measuring technique was further prompted by the results from a previous p i l o t study (Toussaint, 1969), which shoved that i t was possible to d i f f e r e n t i a t e handled, shocked, and nonhandled rats by t h e i r degree of 7 suppression of lever pressing induced by the presentation of a signal which had been previously paired with shock. Relationship between Emotionality and Learning A t h i r d purpose of this study was to determine the extent to which the learning measure could be related to various measures of emotionality (e.g. latency of emergence from the cage, locomotor a c t i v i t y , etc). This could possibly give some information regarding the relationship between associative learning and other behavioral measures. Of special interest was the relationship between the learning score and locomotor a c t i v i t y . As mentioned above, locomotor a c t i v i t y has been generally confounded i n many standard learning tasks p a r t i c u l a r l y i n those i n which response latency i s used to in f e r learning. The extent of the relationship between learning and a c t i v i t y could indicate the degree to which locomotor a c t i v i t y would be related to the learning task here used. 8 METHOD Subj ects. Twenty-nine male hooded rats derived from the Long-Evans s t r a i n , bred i n the animal colony of the Department of Psychology of the University of B r i t i s h Columbia, were used. After b i r t h , pups within each of nine l i t t e r s were randomly assigned to each of three conditions: a shocked (S), a handled (H), and a nonhandled condition (NH). The pups were housed by l i t t e r s u n t i l they were 22 days old at which time they were weaned and placed i n i n d i v i d u a l cages. The S and NH groups had 10 Ss each and the H group had nine £>s. Disparity i n the number of Ss was the r e s u l t of the death of one of the handled jSs during the period between weaning and testing. Apparatus. Preweaning treatments: Preweaning treatments were carried out i n two s i m i l a r settings. The shock box had inside dimensions of 10 x 10 x 8% i n . , sides and back of aluminum, front and top of transparent plexiglass, and a f l o o r composed of 18 brass bars 5/32 i n . i n diameter and on 9/16 i n . centers. The handling box had inside dimensions of 11 x 11 x 9h i n . , three sides and the top of transparent plexiglass, the fourth side of aluminum, and the f l o o r composed of 15 stainless s t e e l bars 5/32 i n . i n diameter spaced on 12/16 i n . centers. Both boxes were divided into two equal compartments by a masonite panel so that two S_s could be contained simultaneously. The shock source was a matched impedance source (164K i n series with S) with intensity levels specified i n terms of source voltages. Postweaning tests: The emergence-from-the-cage test and the bright-ness discrimination test were carried out i n the apparatus schematized i n F i g . 1. The u n i t , constructed of plywood and painted f l a t gray, 10 consisted of three parts which could be seri a l l y connected: a home-cage l i d , a runway, and a discrimination chamber. Entrances to the runway and discrimination chamber were blocked by masonite guillotine doors. The top of the three parts were made up of transparent plexiglass and the floor of wire mesh. The runway had two lines painted on the floor, one at the start and the other 12 in. from the start. During testing in the discrimination chamber the top was covered with a one-way mirror underneath which there was a 6W cool white light bulb placed across the center of the top of the chamber. The bulb was covered with a paper towel i n order to diffuse the light and reduce the light intensity. The luminance level provided by the source inside the chamber averaged (measured at nine spots) 37.6 mL. The back wall of the disdrimihation chamber had two circular openings lh i n . in diameter, 1 3/4 in. apart, and- 1/4 in . above the floor level. Behind the wall there was a sliding panel with three openings which matched in size and separation those in the back wall of the chamber. These openings were covered with 2 x 2 in. masonite hinged doors which in the front side had the appropriate discriminative stimuli, black br white covers. Next to the bottom of the panel there was a sliding base on which there were three fixed plastic water cups of 5 cc, capacity spaced 1% in. apart. During the sessions one of these cups was f i l l e d with a 4% by volume sugar in tap water solution. When two of the openings in the panel were placed to match those in the back wall, pushing of the hinged doors gave access to the cups. Fear-conditioning t r i a l s were administered in the previously described handling box. The signal, delivered to the box through a loud-speaker, was a 20 db white-noise signal from a Grason-Stadler Noise a Generator, Model 455C. A 200v shock of .10-sec duration Immediately followed each presentation of the 10-sec signal. The drinking suppression test was carried out i n a S c i e n t i f i c Prototype lever box Model A106 which had inside dimensions of 9 1/8 x 8 x 8 i n . , front and back of aluminum and the two sides and top of trans-parent plexiglass. The floor was composed of 16 stainless s t e e l bars, 5/32 i n . i n diameter and spaced on 9/16 i n . centers. The bar and food cup were removed; the l a t t e r was replaced by a removable water bottle attached to the back of the wall whose spout led into the box through an opening i n the lower righ t corner, \ i n . above the g r i d f l o o r . During t h i s session, the 10-sec white-noise signal was presented but not shock was delivered. The number of l i c k s was recorded by a d i g i t a l drinkometer (Physiological Electronics, Inc.). Procedure. Preweaning treatments: A l l infant treatments were ad-ministered from the t h i r d day after b i r t h u n t i l Ss were 22 days old, a t o t a l of 19 d a i l y treatments. At the beginning of each day's session each mother was removed from her nest; a l l l i t t e r s remained separated from the mothers approximately 35 min. At the end of each session each mother was replaced to her respective l i t t e r . Every day each S_ except those i n the NH group, was i n d i v i d u a l l y picked and marked at the base of the t a i l with one of various colors of ink i n order to allow E_ to i d e n t i f y S_s assigned to the d i f f e r e n t conditions within a given l i t t e r . Ss i n the S group were placed, two at a time, i n the shock box and administered an intermittent shock of 75v and .10 sec duration with an intershock i n t e r v a l of .50 sec for a three-min period. Ss i n the H group were simply placed, two at a time, i n the handling box for a period of three min. The NH Ss remained 12 undisturbed i n the nests. Postweaning maintenance and testing. S_s were weaned at 22 days of age at which time they were housed i n i n d i v i d u a l cages. They were maintained on ad l i b , food and water u n t i l they were 62 days old when they were put on a deprivation diet of approximately 15 gms. of Purina Rat Chow per day with one hour a day ad l i b , water. Ss were maintained on the schedule for f i v e days before testing and throughout the remainder of the experiment. On testing days Ss were fed the 15 gms. of chow one hour after the end of each in d i v i d u a l session. Emergence-from-the-cage test; For the emergence-from-the-cage test the cage l i d was hooked onto the home cage and also connected to the runway i n the manner depicted i n F i g . 1. Five minutes after connecting the parts and when the animal was oriented towards the g u i l l o t i n e door, the door was raised. From this moment on and for the next 10 min the following measures were recorded: (1) latency of f i r s t emergence, (2) latency of f i r s t cross of the middleline of runway, (3) t o t a l number of crosses of the runway's middleline and (4) time spent i n the home cage. Adaptation session to the discrimination chamber: The adaptation session followed immediately after the emergence-from-the-cage test. Each S_ was forced to return to the home cage by l i f t i n g the far end of the runway thus t i l t i n g i t and making the S_ s l i d e towards the home cage. This procedure was necessary only i n a few instances since most S_s were i n the home cage or i n i t s v i c i n i t y by the end of the 10-min period. The g u i l l o t i n e door of the cage l i d was replaced, the runway removed, and the home cage connected d i r e c t l y to the discrimination chamber. Five min after connecting the parts, and when the animal was oriented towards the 13 entrance of the chamber, the g u i l l o t i n e door was l i f t e d . Latency of entrance into the discrimination chamber was recorded. After S_ entered the chamber, the g u i l l o t i n e door was replaced i n order to prevent re-entry into the home cage. Ss were l e f t i n the chamber for 25 min during which period both openings had the doors removed. A 4% sugar water solution was available i n the cups behind the openings. After Ss had drunk at least two times from each cup, the openings were closed by s l i d i n g the back panel. Such motion made Ss move away from the openings. When S_s were not facing the openings, openings were again presented, thus making water accessible again. The procedure was repeated several times i n order to force S_s to retreat at the s l i d i n g of the panel and drink during the time allowed. Discrimination Training: On the f i r s t day of discrimination t r a i n -ing, 24 hrs after the adaptation session, both openings had the doors removed and water was available i n both cups. After j> had drunk once from each cup, openings i n the s l i d i n g panel were covered with the discriminative s t i m u l i , black and white hinged doors, and only the cup behind the rewarded door was f i l l e d with water. From then on water was available only by pushing the appropriate door. When Ss pushed either door, they were allowed to drink or inspect (when they pushed the wrong door) for a f i v e -sec period. After t h i s time, the panel was noved to the righ t or to the l e f t thus making the discriminative s t i m u l i inaccessible. This sequence was considered as one t r i a l . When Ss were not facing openings and preferably when they were away from them, the s t i m u l i were presented again. For half the J3s i n each group the rewarded stimulus was the black door and for the other half the white door. The sequence of positions 14 of the positive stimulus i n t h i s simultaneous two-choice brightness discrimination task was determined by Fellows' (1967) discrimination series. Ss were given 20 d a i l y t r i a l s for s i x consecutive days. The t o t a l time i t took Ss to make the 20 choices on the f i r s t day was recorded. Through-out the adaptation and the discrimination sessions Ss were observed by means of a one-way mirror. Drinking suppression test: Ss were f i r s t given a preconditioning drinking test immediately after the l a s t discrimination session. For t h i s drinking test each S_ was placed i n the lever box provided with the water b o t t l e containing a 4% sugared water solution. As soon as S_ started to drink a 10-sec white noise signal was presented on the average of once every minute u n t i l 12 presentations were completed. Licks during and i n the absence of the signal were recorded. Conditioned fear training was given four hrs after the preconditioning drinking test. Ss were placed i n the conditioning box and presented 12 pairings of the 10-sec white noise signal immediately followed by a 200v shock of .10 sec duration, on the average of one presentation of signal and shock per minute. The conditioned emotional response test was administered 24 hrs af t e r the conditioned fear t r a i n i n g . j>s were again placed i n the box provided with the water b o t t l e containing the 4% sugar water solution. As soon as S_ began l i c k i n g , the 10-sec white noise signal was presented again on the average of once every minute u n t i l 12 presentations were completed but th i s time no shock followed i t . The number of l i c k s during and i n the absence of the signal i n both the pre- and post-conditioning drinking sessions were compared by transforming them into suppression r a t i o s . In the formula b/a+b, b_ represented the rate of l i c k i n g during the time the 15 signal was on and a_ the rate of licking during the time the signal was not on. According to this ratio, .50 indicates no suppression of the licking response during the signal with respect to the licking response during the time the signal was not on; values above .50 indicate increase rather than suppresion, and values below .50 indicate suppression. 16 RESULTS In order to achieve an equal number of Ss In each group, one S_ from the S group and one S_ from the NH group were randomly eliminated. The resu l t i n g number of Ss i n each group was nine (n=9). Emotionality measures. Natural log transformations of the time measures expressed to the .10 sec were carried out i n order to reduce v a r i a b i l i t y . One-way analyses of variance were conducted on a l l the tests except on the suppression r a t i o s during the pre- and post-conditioning drinking sessions on which a two-way analysis of variance was performed. 1) Latency of 1st emergence. As Tables 1 and 2 indicate, comparison of the group means on t h i s measure revealed no s i g n i f i c a n t differences among the groups (F=.91, df=2/24, p>.42). 2) Latency of 1st cross. Analysis of the group means showed a s i g n i f i c a n t meain effect (F=4.98, df-2/24, p<.01). The data analysis summarized i n Tables 3 and 4, indicated that the s i g n i f i c a n t effect was the r e s u l t of a s i g n i f i c a n t difference between the means of the S group, 1.75, and the mean of the H group, 4.01 (HSD=2.26, p<.05) as tested by Tukey's HSD (honestly s i g n i f i c a n t difference) s t a t i s t i c for multiple comparisons of means (Tukey, 1953). The NH group did not d i f f e r s i g n i f i -cantly from the S or the H group (p>.05). 3) Number of crosses i n the runway. For t h i s measure, as shown i n Table 5, the S group exhibited the greatest number of mean crosses, 14, and the NH group exhibited the least number of crosses, 9. However, the differences between the means were not s t a t i s t i c a l l y s i g n i f i c a n t (F=.83, df=2/24, p>.45). Analysis of variance i s summarized i n Table 6. 17 Table 1 Transformed (log e) Means and Standard Deviations of the Latencies of Fi r s t Emergence Handled Shocked Nonhandled Mean SD Mean SD. Mean SD 4.14 1.58 3.57 .61 4.08 .94 Table 2 Summary of Analysis of Variance of Latencies of Fir s t Emergence Source M S df F p Treatment 88.535 2 .91 .418 Within 96.633 24 Total 26 — Table 3 Transformed (log e) Means and Standard Deviations of the Latencies of Firs t Cross Handled Shocked Nonhandled Mean SD Mean SD Mean SD 4.01 1.66 1.75 1.06 2.16 1.75 Table 4 Summary of Analysis of Variance of Latencies of First Cross Source MS Treatment 13.084 Within 3.433 Total df F p 2 4.98 .01 24 26 19 Table 5 Means and Standard Deviations of the Number of Crosses Handled Shocked Nonhandled Mean SD Mean SD Mean SD 11 8.3 14 4.7 9 6.4 Table 6 Summary of Analysis of Variance of the Number of Crosses Source MS df F p Treatment 52.481 2 .83 .45 Within 63.065 24 Total — 26 2d 4) Time spent i n the home cage. The analysis of t h i s measure summarized i n Tables 7 and 8 d i d not r e v e a l s i g n i f i c a n t d i f f e r e n c e s among the group means (F=1.90, df=2/24, p>.16). I t i s apparent that i n t h i s measure as w e l l as i n the previous ones the v a r i a b i l i t y i n the scores of the H and NH groups expressed by the standard deviation was larger (SD=.66 and SD=.84, resp e c t i v e l y ) than that of the S group (SD=.47). 5) Latency of entrance to the d i s c r i m i n a t i o n chamber. Analysis of t h i s data, summarized i n tables 9 and 10, indicated a s i g n i f i c a n t main e f f e c t (F=6.43, df=2/24 s p<.005). The S group had the shortest mean latency, 3.26, which was s i g n i f i c a n t l y d i f f e r e n t from the mean l a t e n c i e s of the H group, 4.61, and the NH group, 5.07 (HSD=-1.35, p<.05 and HSD=»1.81, p<.01, r e s p e c t i v e l y as tested by Tukey's HSD s t a t i s t i c ) . The H and the NH groups d i d not d i f f e r s i g n i f i c a n t l y from each other (HSD=.46, p>.05). The corresponding three mean l a t e n c i e s , 1st emergence, 1st cross, and 1st entrance, f o r each group are depicted i n Fig. 2. This graph shows that for the latency of entrance into the d i s c r i m i n a t i o n chamber the NH group exhibited a longer latency than any of the manipulated groups. This trend i s opposite to that of the latency of 1st emergence and 1st cross i n which i t was the H group which took the longest time to emerge. 6) Time ( i n min) to make the f i r s t 20 choices. The analysis summarized i n Tables 11 and 12, indicated a s i g n i f i c a n t main e f f e c t ( F*4.58, df=2/24, p<.02) which was produced by a s i g n i f i c a n t d i f f e r e n c e between the S group, with the shortest mean time, 29.88 min* and the NH group, with the longest time, 54.55 min (HSD=?4.67, p<.02, Tukey's 21 Table 7 Transformed (log e) Means and Standard Deviations of the Time Spent i n Home Cage Handled Shocked Nonhandled Mean SD Mean SD Mean SD 5.50 .66 4.93 .47 5.49 .84 Table 8 Summary of Analysis of Variance of Time Spent i n Home Cage Source MS df F p Treatment 97.510 2 1.90 .16 Within 51.279 24 Total 26 22 Table 9 Transformed (log e) Means and Standard Deviations of the Latencies of Entrance to Discrimination Chamber Handled Mean SD 4.61 .91 Shocked Mean SD 3.26 .64 Nonhandled Mean SD 5.07 1.43 Table 10 Summary of Analysis of Variance of Latencies of Entrance to Discrimination Chamber Source MS df F p Treatment 7.976 2 6.43 .005 Within 1.239 24 Total 26 u p Co o 5 -8> oo 8 s o C O 3-2-• O • NONHANDLED O HANDLED A SHOCKED O • A o A • A 1st em erg. Lat. of cross Lat. entrance to discr. chamber Figure 2. Transformed (log e) latencies of f i r s t emergence, f i r s t cross, and entrance into the discrimination chamber. 24 Table 11 Means and Standard Deviations of the Time i n Min. Taken to Make F i r s t 20 Choices Handled Shocked Nonhandled Mean SD Mean SD Mean SD 43.66 20.54 29.88 12.66 54.55 14.80 Table 12 Summary of Analysis of Variance of Latencies of Time Taken to Make F i r s t 20 Choices Source MS df F p Treatment 383.14 2 4.48 .02 Within 300.46 24 Total 26 25 HSD s t a t i s t i c ) . The H and the NH groups did not d i f f e r s i g n i f i c a n t l y from each other (HSD=10.89, p>.05). 7) Suppression r a t i o s during the pre- and post-conditioning drinking sessions. Analysis of these measures, summarized i n Tables 13 and 14, indicated that a l l the groups underwent a suppression i n t h e i r drinking response as a resu l t of the fear conditioning (F*10.84, df=l/21, p<.005) but that there were not differences i n the suppression r a t i o s due to the treatment conditions (F=.139, df=2/21, p>.05). Learning measure. Data from the discrimination sessions was analyzed by a one-way analysis of variance for repeated measures. The analysis, summarized i n Tables 15 and 16, showed a s i g n i f i c a n t Treatment effect (F=49.53, df=2/24, p<.001), as we l l as a s i g n i f i c a n t Day effect (F=28.57, df=5/120, p<.001) and a s i g n i f i c a n t Day x Treatment interaction (F==2.41, df=10/120, p<.Ol). The mean number of correct choices for each group as a function of t r a i n i n g sessions was plotted i n F i g . 3. In order to assess the s i g n i f i c a n t interaction, a simple main effects analysis of variance was carried out. A summary of t h i s analysis, presented i n Table 17, indicated that the groups did not sta r t to d i f f e r u n t i l the fourth day of t r a i n i n g . The s i g n i f i c a n t difference was maintained through the s i x t h day of t r a i n i n g . Multiple comparisons of the means of each group for days 4, 5 and 6 were carried out i n order to determine which group or groups were producing the s i g n i f i c a n t differences. Pairwise mean comparisons by Tukey's HSD s t a t i s t i c indicated that for a l l the three days the S group, with the greatest number of mean correct choices throughout a l l the sessions (Fig. 3), diff e r e d s i g n i f i c a n t l y from the NH group (HSD=6.05, p<.001; HSD=6.18, p<.001; and HSD=5.37, p<.001 for 26 Table 13 Means and Standard Deviations of the Suppression Ratios During the Pre- and Post-conditioning Drinking Tests Handled Mean SD Pre .381 .082 Post .220 .140 Shocked Mean SD .336 .093 .248 .150 Nonhandled Mean SD .386 .054 .154 .150 Table 14 Summary of Analysis of Variance of Suppression Ratios During the Pre- and Post-conditioning Drinking Tests Source MS df F p Total 26 — -Shock 4284.47 1 10.84 .005 Treatment 55.05 2 .139 n.s. ShxT 288.02 2 .728 n.s. Error 395.296 21 27 Table 15 Means arid Standard Deviations of the Number of Correct Choices i n the Discrimination Task Handled Shocked Nonhandled Mean SD Mean SD Mean SD 13 1.81 14 1.41 11 1.32 Table 16 Summary of Analysis of Variance of the Number of Correct Choices Source MS df F p Treatment 144.34 2 49.53 .001 Error, 15.35 24 b Day 83.26 5 28.57 .001 D X T 7.01 10 2.41 .01 Error 2.91 120 Total 161 Figure 3. Mean number of correct choices i n the discrimination task as a function of training day, for the Handled (H), Shocked (S) and Nonhandled (NH) groups. 29 Table 17 Simple Main Effects Analysis of Variance of the Mean Number of Correct Choices over the Sixth Training Sessions Source Between Subjects Between T at s. Within Cel l s Within Subjects Between S at t. Treatment x Session Error w Total MS 6.33 10.81 5.48 51.37 56.48 48.93 4.98 32.29 54.92 97.29 7.01 2.91 df 2 2 2 2 2 2 144 5 5 5 10 120 161 1.26 2.16 1.09 10.30** 11.32** 9.81** 11.08** 18.85** 33.39** 2.41** * * s i g n i f i c a n t with p<.01 T = treatment S = session 30 the 4th, 5th, and 6th day respectively). The S group differed s i g n i f i -cantly from the H group only on the 5th day (HSD=3.7, p<.05). The NH and the H groups differed significantly from each other on the 4th and 6th training sessions (HSD=4.33, p<.05 and HSD=4.62, p<.01, respectively). Relationship among the dependent variables. The nine dependent variables measured were intercorrelated in order to determine the degree of relationship among them p.s expressed by Pearson r_ coefficients. The intercorrelation matrix appears in Table 18. ?:xtean out of the 36 inter-correlations were s t a t i s t i c a l l y significant (Fisher's Z transformation, df=25). A breakdown of the table showed a main cluster of variables that intercorrelated positively with each other and correlated negatively or not at a l l with the rest of the variables. The obvious cluster is that composed of a l l the time measures (Table 19). The number of crosses in the runway, a rough measure of locomotor activity, was negatively correlated to a l l the time measures. The learning measure (row 1 in Table 18) was also negatively correlated or not correlated at a l l to the latencies and time measures, and i t only showed, a significant positive correlation with the number of crosses in the runway (r-~.39). Within the cluster of time measures i t is of interest that a l l emergence scores did not inter-correlate highly. The lack of high positive correlations among the latency measures could be partially attributed to the. reversal of scores for the NH group (Fig. 2). The suppression ratios during the pre- and post-conditioning sessions correlated significantly with each other (r=.41) which indicated that Ss tended to have similar suppression ratios i n both measures. Both suppression ratios showed very low or no correlation with the rest of the 1 Learning measure 2 Lat. of 1st emerg. 3 Lat. of 1st cross 4 Time i n home cage 5 Lat. of entrance into d i s . chamber 6 Number of crosses 7 Time taken to make f i r s t 20 choices 8 Suppression during preconditioning 9 Suppression during po s t cc nd i t ioning * s i g n i f i c a n t with p<.05 *si g n i f l e a n t with p<.01 Table 18 Correlation Matrix of the Dependent Variables 1 2 3 4 5 6 1.00 -.40* .01 -.34 -.53** .39* 1.00 .32 .58** .39* -.68** 1.00 .46** .13 -.57** 1.00 .53** -.69** 1.00 -.26 1.00 7 8 9 -.47* .03 .10 .23 -.08 -.31 .27 .10 .05 .54** .09 -.30 .61** .26 -.35* -.41** .07 .19 1.00 .18 -.19 1.00 .41** 1.00 Table 19 Correlation Matrix of the Time Dependent Variables 3 2 1 Lat. of 1st emorg. 2 Lat. of 1st cross 3 Time i n home cage 4 Lat. of entrance into d i s . chamber 5 Time taken to make f i r s t 20 choices 1 2 3 4 5 1.00 .32 .58** .39* .23 1.00 . 46* * .13 .27 1.00 .53** .54** 1.00 .61** 1.00 * s i g n i f i c a n t with p<.05 * * s i g n i f i c a n t with p<.01 33 emotionality measures. The suppression r a t i o s during the pre-conditioning session showed no s i g n i f i c a n t correlation to any of the rest of the measures. The suppression r a t i o s during the post-conditioning session, on the other hand, correlated s i g n i f i c a n t l y only with the latency of thir d emergence (r=-.35). Because of the pattern of correlation of the learning scores with the time measures, and with the a c t i v i t y measure, the correlation c o e f f i c i e n t s between the two sets of data were squared i n order to obtain the degree of variance accounted i n one variable by the sp e c i f i c a t i o n of the other. The squared Pearson r_ co e f f i c i e n t s are shown i n Table 20. The maximum percentage of common variance was 28% between the emergence into the discrimination chamber and the learning score. The learning measure and the number of crosses i n the runway shared 11.56% of common variance. Table 20 2 Correlation Coefficients and r between Learning and Emotionality Scores Measure r r ^ Lat. of 1st Emerg. -.40 16.3 Lat. of 1st Cross .01 00.0 Time i n Home Cage -.34 11.5 Lat. of Ent. -.53 28.4 Time to make 1st 20 choices -.47 22.5 Supp. during pre-conditioning .03 00.00 Supp. during post-conditioning .10 00.01 Number of Crosses .39 15.21 3 5 DISCUSSION Emotionality Measures The emotionality data indicated that the handled and nonhandled subjects did not d i f f e r s i g n i f i c a n t l y from each other i n emotionality and that only the shocked subjects d i f f e r e d s i g n i f i c a n t l y from the nonhandled ones. This outcome i s contrary to those obtained by numerous studies i n which the handled rats have been found to be less emotional than the nonhandled rats (Ader, 1965; Goldman, 1965; Denenberg and Smith, 1963; Denenberg, Carlson and Stephens, 1962; Levine, 1957, 1950). One reason why the handled and nonhandled did not d i f f e r i n emotionality could be related to the postweaning conditions to which the subjects were exposed. After weaning rats were housed i n a general colony room but, because of unforeseen circumstances, they were exposed to loud noises and other sources of environmental stimulation. Several findings indicate that various postweaning environmental conditions produce d i f f e r e n t i a l effects on adult emotionality tests. McMichael (1966) found di f f e r e n t patterns of drinking i n a water consumption test depending on. whether the animals tied been kept after weaning i n a colony room i n which they received a great deal of stimulation from the environment or kept i n a control room which provided minimal environmental stimulation. McMichael's (1966) data indicated that the handled and control groups reared i n the colony room did not d i f f e r from each other i n the water consumption t e s t , while the shocked groups, maintained also i n s i n i l a r conditions, di f f e r e d s i g n i f i c a n t l y from both the control and the handled group. Such results are i n agreement with the ones obtained i n the present study. 36 Another instance of differential effects of environmental post-weaning stimulation on subsequent adult emotionality tests is provided by a study by Denenberg, Schell, Karas, and Haltmeyer (1966) in which activity in the open f i e l d of handled and nonhandled rats reared in a quiet room and after weaning maintained in a noisy room, was found to be decreased relative to the open f i e l d activity of similarly reared rats which after weaning were maintained in a quiet environments On the basis of these findings, i t could be hypothesized that the present postweaning conditions decreased emotionality differences between handled and nonhandled subjects. The direction of the present emotionality findings does support previously obtained results in which preweaning handling and preweaning shock have been found to produce different effects on emotionality; data is especially in accordance with that of previous studies in which the shocked rats have appeared less emotional than the handled and nonhandled ones (Henderson, 1967; Ader, 1966; McMichael, 1966; Denenberg and Klino, 1964). It can be concluded that the shocked rats were the least emotional of the three groups despite some apparent contradictions in the latency of emergence measures. The latency of emergence measures are purported to measure the degree or tendency to explore a novel situation; and highly emotionally reactive rats have been found to exhibit longer latencies to explore novel situations (Denenberg, 1967). In the present data of the three latency measures taken only in one, latency of entrance to the discrimination chamber, did the nonhandled subjects show significantly longer latencies than the other groups. Greater activity and exploratory behavior by the more emotional rats has been reported i n other experiments. 37 Salama and Hunt (1964) found that nonmanipulated subjects on the f i r s t day of testing i n a T maze showed equal or shorter latency measures than the manipulated subjects, while on the second day of testing the manipulated subjects were s i g n i f i c a n t l y more active than the non-manipulated ones. Whtmbey and Denenberg (1967) also found that on the f i r s t day of testing on the open f i e l d nonhandled rats showed greater a c t i v i t y and shorter latencies to emerge than handled rats while on sub-sequent test sessions the reversal relationship was obtained. The high a c t i v i t y scores on the f i r s t day were also highly correlated with other emotionality measures (e.g. defecation). Whimbey and Denenberg concluded that greater a c t i v i t y on the f i r s t day of testing i n a novel s i t u a t i o n can be indica t i v e of high emotionality rather than low emotionality and t h i s conclusion i s supported by other findings (Welker, 1957, 1959; Salama and Hunt, 1964) but also, depending on the characteristics of the novel s i t u a t i o n , i t can be i n d i c a t i v e of high exploratory tendencies (Hayes, 1960). For the present study a f e a s i b l e explanation of why the emergence measures for each group did not correspond i n d i r e c t i o n and extent with each other i s provided by some relationship obtained by Lester (1967, 1968) regarding the amount of exploratory and the fear arousing properties of the s i t u a t i o n . On the basis of his findings, Lester (1967, 1968, 1969) has proposed that mild fear f a c i l i t a t e s exploratory behavior whereas strong fear i n h i b i t s i t . Lester has defined fear arousing properties i n terms of the novel elements present i n the s i t u a t i o n . Lester (1968) has also hypothesized that exploratory behavior i s affected by the basal fear of the animal. Concerning the 38 latter proposition, Lester (1968) found that fearful rats, so rated on the basis of their defecation scores, tended to be more active than less fearful rats in a situation, open field, presumed to produce mild fear arousal. The opposite relationship was obtained when the comparison was made under a presumably more fear arousing condition such as an elevated maze. In the present study, a comparison of the two loci into which the Sis entered upon their emergence from the home cage revealed that they differed greatly in their degree of novelty. While the first emergence led into the narrow gray runway, illuminated only by the light coming from the room lamp, the emergence into the discrimination chamber led into a relatively wide area, brightly l i t , and with extra stimuli such as the two openings in the back wall (Fig. 1). On the basis of the physical discrepancies of the two settings from the characteristics of the home cage characteristics and according to Lester's findings, it can be said that the two situations differ in their degree of fear arousing properties. It is in the least novel of the two settings that the nonhandled group* presumably the more emotional group, exhibited shorter latencies than the handled group. In the more novel setting, the discrimination chamber, the nonhandled group took a significantly longer time to emerge into it and a significantly longer time to make the first twenty choices. The degree of novelty of the situation appeared to have affected the nonhandled and handled subjects. The shocked rats exhibited the shortest latencies to emerge despite the characteristics of the situation. Drinking Suppression Test The other aspect of the emotionality data concerned the suppression 39 test. Leaf and Muller's <1965) technique for measuring conditioned fear did not d i f f e r e n t i a t e among the various treatment groups; however, i t did produce a signifleant;suppression effect as a res u l t of the fear conditioning. The reason for the f a i l u r e of t h i s technique to distinguish among tfie groups i s not readily apparent. Since t h i s test was carried out a f t e r the rats had been exposed to s i x days of consecutive testing, i t i s possible that by the end of t h i s period the emotionality differences might have attenuated. A conditioned fear measuring procedure based on the suppression of a leverpressing response which was used i n a previous p i l o t study (Toussaint, 1969) was successfnl i n differentiati - i & among the groups even though the suppression test was administered a f t e r 11 days of lever-press t r a i n i n g . Maybe within the drinking suppression test a more sensitive measure of the degree of suppression produced by the conditioned signal would be the rate of recovery of the o r i g i n a l consummatory l e v e l ov2r a period of days. Learning Measure One important aspect of t h i s study concerned whether the preweaned shocked, preweaned handled, and unmanipulated rats d i f f e r i n an appetitive learning task i n which the locomotor requirements to obtain the reward have been minimized. The differences observed during the l a s t three days of t r a i n i n g indicated that both the handled and shocked groups diff e r e d from the control group but that the handled and the shocked group did not show consistent s i g n i f i c a n t differences from each other. Learning seemed to be affected by manipulation as such but not d i f f e r e n t i a l l y by the s p e c i f i c type of manipulation. The important question concerning these results i s whether the 40 behavior reflected i n the learning measure i s different from that represented i n the emotionality scores. While i n the learning data both handled and shocked groups diff e r e d s i g n i f i c a n t l y from the control group, i n the emotionality measures only the shocked group differed from the control. Despite the differences i n the patterns of results there i s the p o s s i b i l i t y that differences i n emotionality were reflected i n the learning scores. Relationship between Emotionality and Learning An indication that emotionality and learning could have been related Is suggested by the pattern of relationship of the emotionality and learn-ing measures. The i n t e r c o r r e l a t i o n matrix (Table 18) indicated that s i x of the nine emotionality measures had s i g n i f i c a n t negative correlations with the learning measures and that only the number of crosses i n the runway, a measure of the subjects' locomotor a c t i v i t y , showed a s i g n i f i c a n t p ositive c o r r e l a t i o n with the number of correct choices i n the discrimina-t i o n task (r=.39). To the extent that these correlation c o e f f i c i e n t s indicate the degree to which learning and emotionality variables varied together, i t can be said that learning and emotionality scores were related. I t could be further hypothesized that the emotionality of the subjects somewhat affected the outcome of the learning scores. This l a t t e r proposition i s substantiated by the casual observation that during the discrimination training sessions i f a rat appeared to be emotionally affected by the s i t u a t i o n (e.g. crouched for a long time), i t would tend to remain so throughout most of the entire twenty-trial session. I t appears that, although the learning task was designed to decrease differences i n exploratory behavior and a c t i v i t y , a c t i v i t y s t i l l influenced 41 the learning scores. A c t i v i t y was highly correlated to the other emotionality measures. The pattern of s i g n i f i c a n t correlations seemed to indicate that i f an animal was active, as measured by the number of crosses i n the runway, i t also tended to emerge sooner from the home cage, to cross the runway sooner, to take a shorter time to make the f i r s t twenty choices, and to make a greater number of correct choices. However, even though the learning and emotionality measures were correlated, i t i s also apparent that the extent of th e i r relationship was not very high. The c o r r e l a t i o n c o e f f i c i e n t s between the two sets of data were r e l a t i v e l y low. This i s evidenced by the rather low variances shared by the emotionality and the learning scores (Table 20). The maximum common variance was 28.4% between the latency of entrance into the discrimination chamber and the learning scores. This c o r r e l a t i o n a l data obviously does not t e l l whether indeed emotionality differences affected the learning scores; i t does provide, however, some ideas as to which variables could be manipulated i n order to assess more c l e a r l y the effects of early experiences on emotionality and learning. For instance, a more ide a l way to measure the effects of different degrees of fear arousing situations on the learning of groups d i f f e r i n g i n emotionality could be by f a c t o r i a l l y comparing the learning of handled, shocked, and nonhandled groups on several situations varying i n degree of novelty. I t can be concluded that i n f a n t i l e handling and shock affect learning and emotionality d i f f e r e n t l y . However, whether i n f a n t i l e manipulations w i l l appear to affect learning and emotionality independently, or i n an 42 i n t e r a c t i v e manner, seems to be related to the extent to which the learning task i s dependent on behaviors which are also influenced by emotional reactions. In the present study, for instance, differences i n locomotor a c t i v i t y might have been reflected i n the learning scores. Such differences are d i f f i c u l t to control: but> there s t i l l remains the p o s s i b i l i t y that a learning task or procedure could be devised i n which the r o l e of emotionality could be further minimized or better assessed. I t can also be concluded that the effects of i n f a n t i l e handling and shock are not. unitary. The effects of each manipulation varied i n manner and extent for each of the behavioral aspects measured. This points to the inadequancy of talking about the effects or i n f a n t i l e manipulations on "emotionality" when the various behaviors which have been subsumed under such phenomenon do not seem to vary concomitantly as a result of early manipulations. At t h i s stage, a more f r u i t f u l approach would seem to be one directed at establishing more precise parametric relations between i n f a n t i l e manipulations and s p e c i f i c behavioral aspects. 43 References Ader, R. 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