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An investigation of the Voeks postremity hypothesis Koppenaal, Richard John 1956

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AN INVESTIGATION OP THE VOEKS POSTREMITY HYPOTHESIS by RICHARD JOHN KOPPENAAL A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE HEQUIREMENTS FOB THE DEGREE OF . MASTER OF ARTS i n the Department of P h i l o s o p h y and Psychology We accept t h i s t h e s i s as conforming to the standard r e q u i r e d from candidates f o r the degree of MASTER OF ARTS . Members of the Department of Ph i l o s o p h y and Psychology THE UNIVERSITY OF BRITISH COLUMBIA May, 1956 AN INVESTIGATION OP THE VOEKS POSTREMITY HYPOTHESIS Abstract This experiment was undertaken to investigate the v a l i d i t y of the postremity p r i n c i p l e . This p r i n c i p l e pre-d i c t s , f o r recurring situations, such as maze, that a response to a given s i t u a t i o n w i l l be- the same response that was l a s t made to the stimuli present i n that s i t u a t i o n . The p r i n c i p l e i s hypothesized as ever-operating. The lack of perfect p r a c t i c a l predictions i n the maze situ a t i o n i s explained by the i n s t a b i l i t y of stimuli, e s p e c i a l l y proprioceptive s t i m u l i , from t r i a l to t r i a l at the same choice point. While the importance of proprioceptive s t a b i l i t y upon successful pre-dictions has been f r e e l y hypothesized, very l i t t l e has been done to test t h i s . One s p e c i f i c purpose of the present experiment was to test postremity i n t h i s regard. The other s p e c i f i c purpose of this experiment was to determine i n what way, i f any, successful predictions are related to ' r i g h t 1 responses. I t was noted by one i n v e s t i -gator that the number of successful predictions increased with the number of t r i a l s (and increase i n ' r i g h t 1 responses). The p o s s i b i l i t y of some relat i o n s h i p has Tbeen hinted at by several investigators but never apparently thoroughly explored. A mental maze was used i n t h i s experiment. There were twelve choice points, each one with one ' r i g h t ' and one 'wrong' choice possible. The methods used to control s t a b i l i t y of proprio-ceptive stimuli consisted l a r g e l y of control of motor responses and posture. In one group r e l a t i v e l y l i t t l e control of motor responses or posture was exercised, while i n another group the motor responses and the posture of the subject were held constant. In a t h i r d group the s t i m u l i were varied on cer-t a i n t r i a l s . A fourth group had, i n addition to stimulus constancy, any choice point that e l i c i t e d a 'wrong' response repeated immediately, so that the subject corrected h i s res-ponse. This was done to gain more accurate recording of responses, which was hypothesized as being very d i f f i c u l t when the l a s t response i s 'wrong'. The analysis of the r e s u l t s indicated differences i n the number of successful predictions only between the fourth group (repeated choice points), on the one hand, and each of the other three groups, on the other hand. Thus, no differences were found between the three groups where only s t a b i l i t y of proprioceptive stimuli varied. Purther analysis indicated postremity was a suc-cessful predictor only when i t predicted a ' r i g h t ' response. In r e l a t i o n to t h i s f i n d i n g , a simple prediction of the •right" 1 response at each choice point proved as e f f i c i e n t as postremity. The r e s u l t s led to the conclusion that the obtained differences i n the number of successful predictions between Group IV and the other three groups was due to the incidence of more 'right* responses In this group (which had more p r a c t i c e ) . Thus the r e s u l t s of t h i s experiment did not support the hypothesized importance of stimulus s t a b i l i t y for postremity, arid also provided an analysis which showed i t s successful predictions were coincident with r e p e t i t i o n of fright'*" responses. This r e p e t i t i o n of 'right* responses could be predicted by many theories. The v a l i d i t y of postremity as a p r a c t i c a l predictor and as a t h e o r e t i c a l concept was, within the l i m i t a t i o n s of this experiment, questioned. ACKNOWLEDGMENT The writer would l i k e to express h i s gratitude to Dr. D.T. Kenny f o r o r i g i n a l l y suggesting the area of research and f o r h i s stimulating suggestions and encouragement dur-ing the course of the work. CONTENTS CHAPTER PAGE I. INTRODUCTION AND STATEMENT OF THE PROBLEM . . . 1 Introduction 1 Purpose of the Present Experiment . . . . 16 I I . EXPERIMENTAL MATERIALS, .SUBJECTS AND PROCEDURE , 18. Materials . 18 Subjects 20 Procedure 21 I I I . THE DATA AND THEIR TREATMENT 31 IV.. CONSIDERATION OF THE RESULTS IN RELATION TO THE HYPOTHESES TESTED 1+2 Discussion 1+2 Conclusion * . 1+7 V. SUMMARY 1+9 BIBLIOGRAPHY £2 APPENDICES A. The Mental Maze . f?3 B. . Results of the Analysis of the C r i t e r i o n learned to $1+ % # # * TABLES TABLE PAGE I. Analysis, of Variance of the Number of Correctly Predicted Responses, on T r i a l s 3 , 6 , and 9 3k I I . Differences between the Means of the Four Groups 3$ I I I . Percentage of Correct Predictions by Postremity and the Percentage of 'Right 1 Responses, f o r Each of the Four Groups 3 9 * -£ * . . . CHAPTER I. INTRODUCTION AND STATEMENT OP THE PROBLEM One of the central problems In psychology Is the accurate prediction of behavior. Prom t h i s problem arises the necessity of determining what factors can be used i n the prediction of behaviour i n a given s i t u a t i o n . In t h i s regard many psychologists, have been concerned with the prediction of responses i n maze learning situations. The maze si t u a t i o n i s a f r u i t f u l one f o r analysing the predictive value of ce r t a i n factors because the same situations or stimuli (choice points) recur again and again on succeeding t r i a l s . This makes i t possible to take into account what many theorists have con-sidered one of the main sources of u s e f u l information f o r predicting behaviour i n a given s i t u a t i o n , namely, the prev-ious responses of the organism to that s i t u a t i o n . Thus,, i n a maze situation, the predictive capacity of various theor-e t i c a l methods of taking into account previous responses can be compared and tested. This experiment i s concerned with one s p e c i f i c hypothesis regarding the use of past responses i n predicting the next response to a si m i l a r stimulus s i t u a t i o n . This hypo-thesis has been advanced by Voeks (8) , and was derived from Guthrie's (2) theory of learning. The hypothesis i s s t r i c t l y a recency one, taking into account only the l a s t made response 2 to a s i t u a t i o n and predicts that the same response w i l l be made the.next time the si t u a t i o n occurs. Voeks has termed this hypothesis "postremity" (from the La t i n postremo,. supers l a t i y e of " l a t e " ) . Voeks (8,p.ij .9^) has stated the postremity p r i n c i p l e as follows: In a recurring s i t u a t i o n , such as repeated t r i a l s i n a puzzle-box or maze, the most probable response on any t r i a l i s the one l a s t made to the stimuli present on that t r i a l . I f some tr a n s i t o r y cause a l t e r s the res-ponse, this new response i s the one predicted f o r the ' next t r i a l on which that stimulus pattern occurs. This advantage of the l a s t made response holds even when some other response has had I n d e f i n i t e l y greater frequency. I t i s important to emphasize that what Is being predicted by th i s p r i n c i p l e i s an in d i v i d u a l response, not o v e r a l l perform-ance. In a maze, f o r example, postremity would predict that the response made to choice point A w i l l be the same response as was made to choice point A the l a s t time the i n d i v i d u a l met that choice point. As w i l l be pointed out l a t e r , there are some important q u a l i f i c a t i o n s to t h i s simple prediction, the q u a l i f i c a t i o n s Centering around the issue of the i d e n t i t y of the stimulus s i t u a t i o n at any choice point from t r i a l to t r i a l . Postremity represents an application of Guthrie's o n e - t r i a l , contiguity theory of learning. Voeks ( 8 ) points out that Guthrie himself has accumulated some evidence on o n e - t r i a l learning which i s d i r e c t l y applicable to postremity. She ref e r s to the Guthrie and Horton study ( 2 ) of cats i n a puzzle box, i n which i t was observed that a cat tended to 3 repeat the same " f i n a l movements" In successive escapes from the puzzle "box even though no two cats used the same movements. Such a res u l t Is, of course, exactly what postremity would predict. As Voeks (8) has cogently pointed out i raw data are seldom reported In maze-learning situations, and as a d i r e c t consequence, a study of postremity e f f e c t s i s impossible f o r most published experiments. In one maze-learning experiment, where the raw data are reported, Peterson (ij.,.p.-290) concludes that recency (postremity) i s not a factor i n learning. How-ever, Voeks (8,p.ij.97)» by reanalysing Peterson's data, has shown that postremity was a good predictor of responses, being r i g h t 68.1+ per cent of the time. Such a figure i s beyond chance expectancy. Voeks (8) performed three p a r a l l e l experiments to test postremity and the r e l a t i v e e f f i c i e n c y of postremity versus frequency as predictors In maze situations. According to the frequency p r i n c i p l e , the most frequent past response at a choice point was predicted as the next response at that choice point. In the f i r s t experiment a multiple T f i n g e r maze was used, f o r the secondj a punch-board stylus maze^ and for the t h i r d , a threaded stylus, which necessitated the screwing of the stylus into the holes and out again a f t e r every choice was made. In each case the subject was required to reach a c r i t e r i o n of three successive perfect t r i a l s , In each maze, there were two possible choices at each choice point. k Postremity predictions were found to agree extremely well with, the recorded responses. For the three experiments, Voeks (8,p.5>00) reports mean percentages of correct predictions of 88.7 per cent, 82.3 per cent, and 83.1 per cent. When the postreme response was not the most frequent past response, i t s t i l l occurred about 71 per cent of the time, as compared to 29 per cent f o r the most frequent past response. Osgood (3) has c r i t i c i z e d the int e r p r e t a t i o n of the l a t e r r e s u l t s by pointing out that i n such maze learning, where there i s one r i g h t and one wrong response at each choice point, a subject w i l l frequently give the 'wrong' response to a choice point f o r a fe w . t r i a l s u n t i l he learns the 'right? response, after which he w i l l give t h i s 'right' response consistently. In such a s i t u a t i o n , the prediction on the basis of frequency w i l l be the 'wrong' response u n t i l enough t r i a l s on which the 'right' response occurs b u i l d up to make the 'right' response the most frequent. Thus, the frequency prediction w i l l prove incorrect during t h i s time. He further points out that probably this s i t u a t i o n i s the one where frequency and postremity would most often disagree s ince postremity would be predicting the 'right' response as soon as i t had been made once. Osgood's point can be countered by maintaining that, whether he i s rig h t or not, postremity i s a better p r a c t i c a l predictor, and frequency i s a poor predictor per-haps just f o r the reason he points out. Of more i n t e r e s t , however, i s the p o s s i b i l i t y that he illuminates, namely, that, postremity as a good predictor may be dependent upon the fact that with most subjects i n a maze many choice points are passed c o r r e c t l y on t r i a l a f t e r t r i a l while a few choice point are being 'learned 1. This would give long successions of correct postremity predictions merely because the subject i s giving the same 'right' response on t r i a l a f t e r t r i a l to these choice points. This would be p a r t i c u l a r l y emphasized where the subjects are learning to a c r i t e r i o n of three successive perfect t r i a l s . By d e f i n i t i o n , the l a s t two t r i a l s would have a l l postreme predictions correct, and further; the few t r i a l s preceding the l a s t two would probably have a very large proportion of repeated 'right' responses (while only one or two choice points are s t i l l being 'learned') and thus a very large proportion of postreme predictions would be correct ones However, postremity predictions are often- correct through 'wrong' responses being repeated. The problem here would be to determine just how dependent postremity, as a predictor above chance, i s upon repeated ' r i g h t ' responses. By d e f i n i t i o n , of course, postremity predictions are confined to these two situations. As such, i t may appear meaningless, as f a r as proving postremity the best predictor i n maze situations, to be concerned with whether i t s high predictive rate depends more upon one sequence than another. However, i f postremity as a good predictor i s proven to be e n t i r e l y dependent upon repeated 'right' responses, then some doubt 6 about the g e n e r a l i z a t i o n s p o s s i b l e to o t h e r s i t u a t i o n s where there are no ' r i g h t 1 and 'wrong? responses, o r where t h e r e is. more than one.'right'?' response, would be c r e a t e d . A l s o , the p o s s i b i l i t y a r i s e s of there b e i n g as good or a b e t t e r p r e d i c t o r a v a i l a b l e i n maze s i t u a t i o n s , s i n c e i f p o s t r e m i t y i s e n t i r e l y dependent upon repeated ' r i g h t ? responses then a simple p r e d i c t i o n of the ' r i g h t 1 response f o r every response might prove as good or b e t t e r than p o s t r e m i t y . Thus, by t h i s type of a n a l y s i s , p o s t r e m i t y , b o t h as a p r a c t i c a l p r e -d i c t o r i n maze s i t u a t i o n s and as a more g e n e r a l phenomenon, might be c h a l l e n g e d . Perhaps the h i g h r a t e of postreme p r e d i c t i o n s i n a maze s i t u a t i o n i s merely an a r t i f a c t of. something s i m p l e r and more b a s i c , the r e p e t i t i o n o f ' r i g h t ' responses. I t must be p o i n t e d out t h a t no study which t e s t e d the above two hypotheses ( p o s t r e m i t y dependent upon repeated • r i g h t ? responses, and p r e d i c t i o n of the ' r i g h t ' response as. good as postremity) Could v i t i a t e the p o s t r e m i t y concept. P o s t r e m i t y may be a more g e n e r a l phenomena which,, i n the case of m u l t i p l e T c h o i c e mazes, happens to c o i n c i d e w i t h repeated ' r i g h t ' responses. In such a case repeated ' r i g h t ? responses could be i n t e r p r e t e d as an a r t i f a c t o f the more b a s i c concept of p o s t r e m i t y . The p o i n t b e i n g made here, however, i s t h a t i f . t h e s e two h y p o t h e s i s prove c o r r e c t , then.the proof of. " " M u l t i p l e T maze" w i l l be used h e r e a f t e r to r e f e r t o any maze i n v o l v i n g a number of choice p o i n t s where each Choice p o i n t has two p o s s i b l e c h o i c e s a v a i l a b l e . 7 postremity must l i e somewhere else than In the analysis of responses i n multiple T mazes. There i s another aspect of Voeks' concept which i s c e r t a i n l y related to the foregoing, but can be separated from i t f o r the purposes, of discussion. This aspect can be termed the t h e o r e t i c a l basis of postremity, whereas the above d i s -cussion was p r i m a r i l y concerned with postremity as. a p r a c t i c a l predictor. The question which Voeks i s try i n g to answer i n her theorizing i s : i f the p r i n c i p l e of postremity i s v a l i d , why does a subject not continue forever to make the same response at any given choice point? In other words, why doesn't postremity predict perfectly? The lack of perfect prediction i s not due to some p r o b a b i l i t y factor, as might be gathered from her statement of the p r i n c i p l e . Rather, she (8,p.5>03) considers i t to be due to changes i n the stimulus s i t u a t i o n at choice points from t r i a l to t r i a l and to- the d i f f i c u l t y i n recording the actual 'last-made' response to a choice point. I t w i l l be remembered that, the p r i n c i p l e i s stated i n such a way that i f the s t i m u l i s i t u a t i o n changes from t r i a l to t r i a l at a given choice point then the same response cannot be expected. The changes she hypothesizes as being important i n creating d i f f e r e n t stimulus situations can be c l a s s i f i e d into three d i f f e r e n t categories. F i r s t , and probably mo.st important, are the proprioceptive cues (or movement-produced-stimuli) of the subject. I f the subject changes h i s p o s i t i o n os posture,- h i s whole pattern of proprioceptive cues w i l l be changed. Following Guthrie, Voeks considers these pro-prioceptive cues to be of utmost importance i n learning, being a large part of the t o t a l s t i muli which become associated with a response. I t n a t u r a l l y follows that, i f the proprioceptive pattern changes r a d i c a l l y , the t o t a l stimulus situation, at a choice point w i l l be quite d i f f e r e n t from the stimulus s i t u a t i o n which existed on the l a s t t r i a l at that choice point. Since postremity predicts only the same response f o r the same stimulus s i t u a t i o n , i t i s not- in. error i n t h i s case i f the response i s d i f f e r e n t at the same choice point. Second, there may be differences i n the external stimuli present on d i f f e r e n t t r i a l s : changes i n l i g h t i n g or olf a c t o r y cues, noises, motions by the experlmentor, etc. Third, there are further changes i n the i n t e r n a l stimuli pattern. Such Changes operate e s p e c i a l l y during the f i r s t few t r i a l s when the subject may be tense, excited, and curious which would cause the pattern of i n t e r n a l stimulation to chang rapidl y . But i n l a t e r t r i a l s the subject may also develop feelings of e l a t i o n , depression or anxiety, thus changing the v i s c e r a l s t i m u l i . Likewise, Voeks Considers that fatigue, and possible changes i n energy l e v e l , muscle tonus, may play a part i n changing the stimulus s i t u a t i o n . Voeks concludes (8,p.503) : 9 Occasionally therefore, the stimulus pattern i s quite d i f f e r e n t from that present the l a s t time the subject was at this, choice point. Consequently, at t h i s point a d i f f e r e n t response may be made to t h i s d i f f e r e n t stimulus pattern; and the prediction (based upon the l a s t behavior to a d i f f e r e n t stimulus pattern at the choice point) w i l l be incorrect. This does not mean necessarily that the p r i n c i p l e of postremity i s not completely v a l i d . I t may be. The p r i n c i p l e states what response i s to be expected when the same si t u a t i o n i s re-encountered. However, f o r p r a c t i c a l reasons,, the principle, i s used to predict behavior when only a part of the s i t u a t i o n i s re-encountered (namely: the 'same' choice point). The other main factor which Voeks uses to account f o r the lack of perfect predictions i s the d i f f i c u l t y involved i n a c t u a l l y recording the 'last-made'' response to the stimulus s i t u a t i o n . Predictions, of course, are based upon the l a s t response recorded; whereas the response (accord-ing to postremity) depends upon the l a s t response made to a sit u a t i o n . I f the two are not the same, then the prediction w i l l be wrong. Voeks. hypothesizes that, i f the response is. "'right', then the last-recorded response i s l i k e l y to be the last-made response because the stimuli i n d i c a t i n g that the response i s 'right' usually do. not e l i c i t a d d i t i o n a l responses to that choice point d i f f e r i n g from that recorded. However, i f the response i s 'wrong' then the stimuli following that res-ponse which indicate i t s incorrectness often bring other added responses on that t r i a l to many of the same stimuli that were o r i g i n a l l y present at that choice point, such added responses as movement away from the incorrect a l l e y and toward the correct a l l e y of a maze, or i m p l i c i t verbal p r a c t i c e . 10 Voeks (8,p.502) continues: These responses (which are now the postreme res-ponse to some of the stimuli of that choice point situation) are not recorded, however; and they are d i f -ferent from and incompatible with the one that was recorded. Thus the predictions again could f a i l , even though the theory i s sound. This l a s t point i s of interest concerning the e a r l i e r discussion of the possible dependency of postremity upon repeated 'right' responses. I t i s apparent from the above that Voeks has a ready explanation f o r why 'wrong' responses are not repeated as consistently as 'right' responses. A l a t e r experiment, performed by Voeks, contains re s u l t s applicable to postremity (7)• In t h i s experiment the subject's eye-blinking response was conditioned to a buzz, with a puff of a i r as the unconditioned stimulus. The res u l t s of this experiment, when analysed f o r postremity, showed 81+.6 per cent of the predictions correct f o r i n d i v i d u a l responses. Xn other words, the subject most of the time responded to the buzz (either b l i n k or not) the same way he did the l a s t time the buzz sounded. In this experiment Voeks set out to control the stimulus s i t u a t i o n f a r more r i g i d l y than i s usually,,done, i n consideration of the effects she and Guthrie have hypo-thesized about s h i f t i n g stimulus patterns. A b r i e f consid-eration of the experimental methods she employed to hold constant the stimulus s i t u a t i o n may help to c l a r i f y the 11 controls she believes to be important i n any experiment designed to t e s t the postremity p r i n c i p l e . Throughout each t r i a l the. subject depressed a telegraph key with each hand. This was designed to insure at l e a s t some of the same proprioceptive cues (those r e s u l t -ing from the motor responses required to press the keys) wouid remain constant from t r i a l , to t r i a l . The subject's -breathing was also controlled, so that he held h i s breath as the conditioned stimulus was presented. This, obviously was designed to s t a b i l i z e the s t i m u l i from the muscles of the chest and diaphragm. The subject's movements were further controlled by a head-rest, and having him look at a cross during the t r i a l s . The subjects were given slow, conversat-ional instructions and reassurance i n order to remove e f f e c t s of changing emotional responses. A soundproof room was used and the subject's head was surrounded by a box to l i m i t h i s v i s u a l f i e l d . Voeks considered that fatigue e f f e c t s were controlled by the minimal work Involved i n the eye-blink response and by allowing i n t e r t r i a l rests of from \\$ to 75 seconds. I t i s r e a d i l y evident that these controls are i n keeping with the suspected sources of changes i n stimulus situations., e s p e c i a l l y those of a proprioceptive nature. I t i s important to note that although Voeks goes into great, d e t a i l about sources of important stimulus pattern changes, she nowhere presents evidence that these sources have 12 any ef f e c t on o n e - t r i a l learning or postremity. Postremity i s viewed by her as an ever-operating p r i n c i p l e , dependent f o r p r a c t i c a l predictions upon certa i n requirements of stimulus s t a b i l i t y and accurate recording of last-made responses.. Postremity, then, should vary i n i t s predictive e f f i c i e n c y with varying degrees of stimulus s t a b i l i t y and of accuracy of recording responses. I f i t does not then the whole t h e o r e t i c a l foundation of the p r i n c i p l e would be suspect. (This, of course, assumes a good deal of accuracy i n the control of proprioceptive cues, especially.) However, the high predictive value of the p r i n c i p l e i n c e r t a i n experimental situations would remain, regardless. Oh the other hand i f , as was suggested as possible In the e a r l i e r part of t h i s chapter, postremity^s high rate of prediction was. found to be coincident e n t i r e l y with repeated ' r i g h t 1 responses,, and merely predicting the "'right' response was as good a predictor, then the whole concept of postremity would be highly suspect i f changes i n i t s pr e d i c t i v e rate were not found with varying degrees of stimulus s t a b i l i t y (stimulus s t a b i l i t y In Voeks' sense). Aside from Voeks' own experiments, Waters and Reitz (6) appear to be the only other investigators who have been d i r e c t l y concerned with testing the postremity p r i n c i p l e . They were interested i n examining the influence of s h i f t s i n proprioceptive stimulation upon postremity predictions. Subjects were given l£ t r i a l s through a multiple T fing e r 13 maze. The experimental subjects had t h e i r proprioceptive patterns systematically changed on t r i a l s 11, 12, 13> and This was accomplished by requiring the subject to alt e r n a t e l y s i t and stand; and alt e r n a t e l y use the l e f t and right hand for t racing the maze. Although they report no precise s t a t i s t i c a l analysis of the data, they conclude that postremity predictions were no better f o r the control group than f o r the experimental group. The percentages of correct predictions f o r each group, on each of the c r i t i c a l t r i a l s , are so close that t h i s conclusion i s undoubtedly correct. I t might be argued that, since the changes took place as l a t e as they did i n the learning task, the 'rig h t ' responses were cued to such a large part of the stimulus situations that the attempted changes, produced l i t t l e e f f e c t i n s h i f t i n g these responses. This could follow from Voeks (8,p.f?08) . . However, the data presented do not support t h i s argument. Since, as i s reported,. (6,p.25>7), the subjects were not by the 11th t r i a l even approximating perfect t r i a l s , there must have been quite a few choice points that were s t i l l f ree of th i s e f f e c t . Perhaps fewer errors of predic t i o n might be expected than I f the changes had been introduced e a r l i e r , but some e f f e c t s could be expected to show i n the performance of postremity predictions, i f Voeks Is correct i n her analysis of why postremity i s not a perfect predictor. The experiment by Waters and Reitz also casts some l i g h t on the question of the operation of postremity possibly depending upon ' r i g h t ' responses of the s u b j e c t s . The e x p e r i -ment was d e l i b e r a t e l y designed so t h a t most subjects, would not master the maze. The r e s u l t s showed t h a t approximately 70 per Cent of the responses were c o r r e c t l y p r e d i c t e d by p o s t r e m i t y . The authors a t t r i b u t e the d i f f e r e n c e of t h i s f i g u r e from those r e p o r t e d by Voeks (82 to 89 per cent) to the f a c t t h a t Voeks's s u b j e c t s were c a r r i e d to a c r i t e r i o n of three s u c c e s s i v e p e r f e c t t r i a l s (which assures p e r f e c t p o s t r e m i t y p r e d i c t i o n s f o r the l a s t two t r i a l s , and p r o b a b l y near p e r f e c t p r e d i c t i o n s f o r the immediately p r e c e d i n g t r i a l s ) . The r e s u l t s a l s o showed C l e a r l y t h a t s u c c e s s f u l p r e d i c t i o n s i n c r e a s e d over the s e r i e s of t r i a l s , as d i d the number of ' r i g h t 1 responses. Voeks could attempt to e x p l a i n t h i s i n c r e a s e of s u c c e s s f u l p r e d i c t i o n s by the changing i n t e r n a l stimulus p a t t e r n of the s u b j e c t s f o r the f i r s t , few t r i a l s (due to a n x i e t y , t e n s i o n , c u r i o s i t y , e t c . ) . But t h i s i s h a r d l y adequate to e x p l a i n the Obtained d i f f e r e n c e s i n percentage o f C o r r e c t p r e d i c t i o n s between, f o r example, t r i a l 8 and t r i a l 1$. The f i g u r e f o r t r i a l 8 was 67 per cent,, t h a t f o r t r i a l 1$ was 83 per cent (p.25>6). The authors conclude t h a t p o s t r e m i t y increases, as " l e a r n i n g " i n c r e a s e s , i n o t h e r words., as the s u b j e c t i s mak-in g more and more ' r i g h t ' responses. T h i s c r e a t e s the i m pression t h a t p o s t r e m i t y i s merely s u c c e s s f u l i n p r e d i c t i n g repeated ' r i g h t ' responses ( s i n c e i t can o n l y be s u c c e s s f u l w i t h e i t h e r repeated ' r i g h t ' .or repeated 'wrong' r e s p o n s e s ) . 15 The data reported do not warrant t h i s additional conclusion. I t i s only shown that the number of successful predictions increases at the same time that the number of 'right? responses increases. No r e l a t i o n s h i p is. necessary, though i t may appear probable. I f such a r e l a t i o n s h i p did exist, t h i s could cer-t a i n l y be explained i n terms of the discussion of the accuracy of recording last-made responses. According to Voeks,. when the last-recorded response i s a 'wrong' response, the record-ing i s probably somewhat Inaccurate. I m p l i c i t practice supposedly changes the last-made response, to some of the sti m u l i of the choice point, from a 'wrong' response to a 'right' response. In t h i s way "learning" can be explained, as well as the s u p e r f i c i a l l y apparent improvements i n pre--d i c t i o n . After a 'right' response no change i n the l a s t -made response occurs, the 'right' response i s therefore the postreme response, and t h i s response p e r s i s t s i n succeeding t r i a l s ; while the 'wrong' response i s sometimes not repeated because of the ambiguity of the last-made response. Thus, af t e r a series of t r i a l s a l l 'wrong' responses are eliminated, and postremity predicts at a high rate because a l l the l a s t -recorded responses are 'right?. However, i f a l l postremity i s t e l l i n g us i s that •right' responses are very often repeated and 'wrong' responses are not so often repeated, then postremity as a p r a c t i c a l predictor i s t e l l i n g us nothing that we don't already know. 1 6 I t g i v e s , o f course, a somewhat d i f f e r e n t e x p l a n a t i o n f o r t h i s phenomena than i s u s u a l . T h i s e x p l a n a t i o n , g i v e n above, i s but a p a r t o f the whole theory u n d e r l y i n g p o s t -remity. T h i s theory, b e i n g a o n e - t r i a l c o n t i g u i t y theory, leans h e a v i l y , as does G u t h r i e ' s theory, upon the importance of stimulus s t a b i l i t y , e s p e c i a l l y o f p r o p r i o c e p t i v e s t i m u l i . The p r e c e d i n g a n a l y s i s shows t h a t what i s r e q u i r e d i s : 1 . more c o n c l u s i v e evidence showing whether or not p o s t -remity i s s u c c e s s f u l o n l y i n p r e d i c t i n g ' r i g h t * responses; and 2 . more c o n c l u s i v e evidence on the v a l i d i t y of some of the more t h e o r e t i c a l a spects of the p r i n c i p l e . PURPOSE OP THE PRESENT EXPERIMENT The present experiment was designed to t e s t the p r i n c i p l e o f p o s t r e m i t y i n both i t s p r a c t i c a l and t h e o r e t i c a l a s p e c t s . The t h e o r e t i c a l aspect was t e s t e d by an attempt to v a r y s y s t e m a t i c a l l y the p r o p r i o c e p t i v e cues, from t r i a l to t r i a l , i n one group w h i l e attempting to c o n t r o l r i g o r o u s l y and h o l d constant p r o p r i o c e p t i v e and i n t e r n a l s t i m u l i i n another group, and e x e r t i n g o n l y the u s u a l c o n t r o l o f e x t e r n a l s t i m u l i i n a t h i r d group. A f o u r t h group, i n which an attempt was made to c o n t r o l the accuracy o f r e c o r d i n g of last-made responses, was i n c l u d e d . The stimulus s i t u a t i o n was a l s o h e l d constant i n t h i s l a t t e r group. The p r a c t i c a l a spects of p o s t r e m i t y were t e s t e d i n three ways: f i r s t , by determining i f p o s t r e m i t y was a b e t t e r -17 than-chance predictor; second, by determining the extent to which postremity i s dependent upon repeated 'right' responses for i t s above-chance prediction; and t h i r d , by comparing postremity, f o r predictive e f f i c i e n c y , with a simple pred i c t i o n of the 'right' response. The s p e c i f i c hypotheses are: 1. Postremity w i l l be a better predictor where the proprioceptive and i n t e r n a l s t i m u l i are held constant than where they are systematically varied or l e f t to chance variations, and w i l l be an even better predictor where, added to a stable stimulus s i t u a t i o n , the record-ing of 'last-made' responses i s more accurate than usual. 2. Postremity w i l l be a better-thari-chanc.e pre-d i c t o r (possibly excluding the group where stimuli are systematically varied), and w i l l predict better than a simple prediction of the 'right' response; also, post-remity' s. above-chance predictions w i l l not be e n t i r e l y dependent upon repeated 'right' responses. The methods f o r c o n t r o l l i n g and varying proprio-ceptive and i n t e r n a l s t i m u l i have been drawn eithe r from Voeks* conditioning experiment or designed i n accordance with conditions she and Guthrie have hypothesized as import-ant . CHAPTER II EXPERIMENTAL MATERIALS, SUBJECTS AND PROCEDURE MATERIALS, A mental maze, patterned a f t e r Peterson (2), was used. This maze (see Appendix A) consisted of twelve choice points, each choice point consisting of two l e t t e r s offered verbally by the experimenter. One of the two l e t t e r s of each pair was. the 'right ' choice, the other l e t t e r was the 'wrong' choice ( i n Appendix A, the 'right' l e t t e r i s indicated by an a s t e r i s k ) . In designing t h i s maze the l e t t e r s 'X? and 'Z' were not used as i t was f e l t that a p a i r containing either of them would be more e a s i l y learned than other p a i r s . The remaining l e t t e r s of the alphabet were then paired randomly,, t h e i r order i n the pa i r was likewise randomly determined, as was the 'right' l e t t e r f o r each p a i r , and the order of the pairs i n the maze. Any pa i r of l e t t e r s that spelled a word or any meaningful part of a word was either reordered i n the p a i r or re-paired. [For example, the l e t t e r s 'W and 'E* were randomly chosen i n that order f o r one pair . To eliminate the possible memory f i x i n g value of that pair, the two l e t t e r s were reversed i n order.' S i m i l a r l y , where the order of pairs or of 'right' responses afforded obviously possible memory f i x i n g 19 combinations the pairs were reordered or a new ' r i g h t 1 response was chosen. The subject was. instructed to choose one of the two l e t t e r s i n each p a i r a f t e r that- p a i r had been presented ver-b a l l y to him. His response was recorded and he was then t o l d i f h is response was 'right' or 'wrong'. Ohe room was used f o r testing a l l subjects. This, room had i t s windowa completely blacked out so that i l l u m i n -ation could be s t r i c t l y controlled. The subject, sat i n a straight-back c h a i r at a table of average height. The subject faced a wall e n t i r e l y draped with black curtains. A can, 1$ inches i n diameter and 1$ inches i n height, was placed i n front of and just about four inches above the table. When the subject was. seated, the can was i n a d i r e c t l i n e to the sub-je c t ' s eyes. The can contained a f i f t e e n watt bulb and a small n a i l hole of l / l 6 inch diameter had been pierced i n the surface of the can d i r e c t l y i n front of the subject. The bulb was oh an e l e c t r i c c i r c u i t so constructed that the bulb went on either i f both of two door b e l l buttons were pressed down or i f a throw switch was engaged. The throw switch was located on the experimenter's table,, which was d i r e c t l y behind and out of sight of the Subject. The two door-bell buttons were attached to a small, movable stand on the table i n front of the subject so that, the position of the buttons could be changed to s u i t the reach and comfort of the subject's arms. A few kinds of doorbell buttons were t r i e d , and the ones 20 f i n a l l y used were selected because they did not involve so much work as to cause the subject to fatigue r a p i d l y (as judged by preliminary t e s t s ) . No subject i n the experiment, when asked i f the buttons, had t i r e d h i s fingers appreciably, responded a f f i r m a t i v e l y . A chin rest was so constructed that i t could be moved up and down to accommodate the d i f f e r e n t head heights of the subjects. This chin rest was. placed on the edge of the table d i r e c t l y i n front of the subject. I t had a short section of 2x1). projecting from each side at table l e v e l f o r the subject to rest his. elbows on when h i s hands were on the buttons. The experimenter's table was so placed that the experimenter'was. not v i s i b l e to the subject at any time during the experimental task. The table had, besides the throw switch, a small shaded n i g h t - l i g h t (7 watts) On one side, mounted two inches above the. table on a piece of d u l l surfaced black card-board. The l i g h t was. further shaded from r e f l e c t i n g -On the wall behind i t or towards the subject. The surface of the experimenter's table was Covered with dull-surfaced black cardboard to further l i m i t r e f l e c t i o n (and il l u m i n a t i o n of the room) . SUBJECTS The subjects were eighty-four volunteer u n i v e r s i t y students. The large majority were members of two sections 21 of the b e g i n n i n g psychology course a t the U n i v e r s i t y of B r i t i s h Columbia. The remaining s u b j e c t s were a l l from an advanced psychology .Course i n l e a r n i n g theory. The p o s s i b l e s o p h i s t i c a t i o n o f these s u b j e c t s i s i r r e l e v a n t , to t h i s experiment s i n c e a l l s u b j e c t s were t o l d t h a t the experimental task was a maze to be. l e a r n e d . The s u b j e c t s were randomly assigned to the f o u r experimental groups (so t h a t each group had- twenty-one s u b j e c t s ) upon r e p o r t i n g f o r the experiment. There were f o r t y - f o u r male, and f o r t y female s u b j e c t s . Through random assignment, n e i t h e r males n o r females, predominated h e a v i l y i n any one group. A f t e r the experimental s e s s i o n each s u b j e c t was t o l d t h a t the experiment was. t e s t i n g the d i f f e r e n t i a l e f f e c t s of v a r i o u s c o n d i t i o n s upon l e a r n i n g . He was urged not to i n f o r m others of the nature of the task, so t h a t the r e s u l t s would not be confounded. PROCEDURE Each s u b j e c t was 'run* through nine t r i a l s of the e n t i r e maze. I t was decided to. use t h i s constant number of t r i a l s , r a t h e r than have each s u b j e c t l e a r n the maze to a g i v e n c r i t e r i o n , because i t f a c i l i t a t e d v a r y i n g the s t i m u l u s s i t u a t i o n on the same t r i a l s , f o r a l l s u b j e c t s i n the " v a r y i n g s t i m u l i " group. When the maze was t r i e d on a few p r e l i m i n a r y sub-jects,, almost a l l of them l e a r n e d to be a c r i t e r i o n of at 22 l e a s t ten out of twelve c o r r e c t c h o i c e s by the n i n t h t r i a l . Thus i t was considered t h a t n i n e t r i a l s gave, an adequate sampling of a subject'a, responses i n the maze. Having a s e t number of t r i a l s a l s o i n s u r e d t h a t each subject, would have the same number of t o t a l responses f o r the a n a l y s i s o f the data, which would g r e a t l y f a c i l i t a t e the a n a l y s i s . As f a r as p o s t r e m i t y i s concerned,, a t any r a t e , i t should p r e d i c t as w e l l w i t h this, number of t r i a l s as i f the s u b j e c t l e a r n e d to a c r i t e r i o n . As was p o i n t e d out i n the Introduction., the last, few t r i a l s , , when a s u b j e c t i s l e a r n i n g to a c r i t e r i o n o f two o r three p e r f e c t t r i a l s , are n e c e s s a r i l y h e a v i l y loaded w i t h c o r r e c t postreme p r e d i c t i o n s because of the r e p e t i t i o n o f ' r i g h t ' responses, a very l a r g e percentage of the time. No experiment i s needed to t e s t p o s t r e m i t y t h e r e . GROUP I . T y p i c a l L e a r n i n g C o n d i t i o n s The experimental room was n o r m a l l y i l l u m i n a t e d . The s u b j e c t was. asked to s i t down at the t a b l e . The s u b j e c t was f r e e to move o r change h i s p o s i t i o n w i t h i n the r e s t r i c t i o n s Of f a c i n g the w a l l i n f r o n t o f the t a b l e so. t h a t he c o u l d not see the experimenter. After the s u b j e c t was seated, the experimenter read the f o l l o w i n g i n s t r u c t i o n s : I have a r a t h e r s t r a i g h t - f o r w a r d l e a r n i n g t a s k here. I t c o n s i s t s of p a i r s o f l e t t e r s , such as 'Z' and 'X' which w i l l be presented to you a number of times.• F o r each p a i r one o f the l e t t e r s i s r i g h t and one i s wrong. 23 Your job i s to l e a r n the r i g h t one. I w i l l say each p a i r to you and you w i l l t e l l me which one.of the two l e t t e r s you t h i n k i s r i g h t . Now., the f i r s t time I present a p a i r to you, you w i l l have no i d e a which one o f the l e t t e r s i s right-,, so you merely guess. I w i l l then t e l l you whether you were r i g h t or wrong. Then the next time I say that p a i r you w i l l t r y and remember which one was.right, F o r example, i f I say "Z, X" and you guess- "X" and I say "wrong", t h e n the.next time I say "Z, X" you w i l l t r y and say "Z". There are twelve p a i r s of these l e t t e r s and I w i l l go through and say each one to you i n t u r n , from one to twelve. Then I w i l l go back to the b e g i n n i n g and go through the l i s t again, the same p a i r s i n the same o r d e r . I w i l l do t h i s a g a i n and a g a i n . You w i l l t r y and l e a r n as many o f the r i g h t l e t t e r s as you can. Every time you choose a l e t t e r I w i l l t e l l you whether you were r i g h t or wrong. There i s no p a t t e r n of r i g h t answers,, e i t h e r a c c o r d i n g to the alphabet or a c c o r d i n g to the order the l e t t e r s , are presented i n . So don't bother to l o o k f o r a pattern,-, i t w i l l o n l y h i n d e r your l e a r n i n g . T h i s i s j u s t a simple t a s k of remembering f o r .each p a i r which one of the l e t -t e r s i s r i g h t . Now,: the l i s t Is., n a t u r a l l y , a l i t t l e . Confusing . and d i f f i c u l t so don't expect to l e a r n i t r i g h t away. I t w i l l probably take a l i t t l e , w h i l e . Don't be d i s -couraged because, you Can't remember the r i g h t answers a f t e r o n l y a few t r i a l s . -Now, I f you're ready w e ' l l s t a r t . Remember., the f i r s t time through the l i s t , , you merely guess which l e t t e r o f each i s r i g h t . I f the s u b j e c t had any q u e s t i o n s the pertinent, p a r t of the i n s t r u c t i o n s were read a g a i n . The experimental task was then s t a r t e d and the sub-j e c t was 'run.!1 through the maze n i n e times.. Each p a i r was r e c i t e d by the experimenter and the s u b j e c t was t o l d " r i g h t " o r "wrong" a f t e r - h i s response. With as. l i t t l e pause as pos-s i b l e the next p a i r was then presented. I n t h i s way an attempt was made to keep i m p l i c i t p r a c t i c e at a minimum.. A f t e r the t w e l f t h p a i r had been presented and responded to f o r the 24 f i r s t time (the end of the f i r s t t r i a l ) , the subject, was. informed t h a t t h a t was the l a s t pair,, but b e f o r e s t a r t i n g over again w i t h the f i r s t pair.,: there would be a s h o r t r e s t . Sub-sequently a f t e r each t r i a l (one 'run' through the e n t i r e maze) th e r e was- a t e n second pause. T h i s was i n t r o d u c e d i n order to keep t h i s r e s t constant i n a l l groups^ s i n c e the other groups had the pause i n order to r e s t the f i n g e r s the s u b j e c t s used to p r e s s the d o o r - b e l l buttons. GROUP I I . R i g i d C o n t r o l of the L e a r n i n g S i t u a t i o n The s u b j e c t was seated a t the t a b l e and the c h i n re.st was a d j u s t e d so t h a t the s u b j e c t f e l t comfortable. The s u b j e c t was then i n s t r u c t e d to put h i s elbows on the s i d e b l o c k s o f the c h i n r e s t apparatus and the s m a l l stand was moved c l o s e r or f u r t h e r away to allow the s u b j e c t ' s arms and hands to r e s t comfortably w h i l e he depressed the buttons w i t h h i s middle f i n g e r s . I t was p o i n t e d out to the s u b j e c t t h a t the l i g h t i n the can went on when bot h buttons were, depressed. The overhead l i g h t s i n the room were then turned out, l e a v i n g o n l y the shaded n i g h t - l i g h t on the experimenter<s t a b l e b u r n i n g . Except f o r the n i g h t - l i g h t , the room was i n t o t a l darkness. ".Further, when the s u b j e c t was l o o k i n g a t the small p i n - p r i c k of l i g h t which i s s u e d from the can as he depressed b o t h buttons (or- the experimenter c l o s e d the switch on h i s t a b l e ) he c o u l d probably see n o t h i n g e l s e a t a l l . T h i s 2 ^ e f f e c t was r e p o r t e d by a l l o f the p r e l i m i n a r y subjects-. A p r e l i m i n a r y t a s k , designed to remove some of the i n i t i a l tension,, -.curiosity and excitement of the s u b j e c t s , was giv.en. T h i s t a s k was e x p l a i n e d as a r e act ion-time study. I t c o n s i s t e d of a s e r i e s o f numbers presented v e r b a l l y to the s u b j e c t . The s u b j e c t was asked f i r s t to keep the l e f t b u t t o n pressed, down and upon h e a r i n g the number ' f o u r 1 t o - p r e s s the r i g h t b u t t o n down a l s o . A l i s t of e i g h t e e n numbers was read o f f w i t h an i n t e r v a l of o n e - h a l f second between each. The number 'four' o c c u r r e d f i v e times at random i n the l i s t . The s u b j e c t was then t o l d to. keep the r i g h t b u t t o n down and pr e s s the l e f t b u t t o n a l s o when the number 'four 1' was heard. A s i m i l a r l i s t o f numbers was then read.. The p r e l i m i n a r y t a s k should have r e l i e v e d some of the i n i t i a l tension,, c u r i o s i t y and excitement of the subject,, as w e l l as acquainted him w i t h the experimental apparatus, i n c l u d i n g the l i g h t which was turned on every time he responded, c o r r e c t l y to the stimulus number. A f t e r the t a s k was completed, the s u b j e c t was t o l d he had done q u i t e w e l l on i t and was reas s u r e d t h a t he would p r o b a b l y do q u i t e w e l l i n the- o t h e r h a l f of the experiment. The s u b j e c t was then asked to s h i f t h i s index f i n g e r s onto the buttons and to press, down the buttons w i t h these f i n g e r s , when t o l d t o , f o r the next t a s k . The s u b j e c t was then asked i f he was s t i l l com-f o r t a b l e . He was urged to take a comfortable p o s i t i o n , and to pla.ce h i s f e e t on the f l o o r i n such a manner t h a t he could keep them';tiiere f o r about f i v e minutes, without' moving.-He was. t o l d that- d u r i n g the next task he should move h i s body as. l i t t l e as p o s s i b l e . He was r e a s s u r e d t h a t this, would not be d i f f i c u l t s i n c e the t a s k would take o n l y about f i v e , minutes, (the a c t u a l average time was Close to seven m i n u t e s ) . The i n s t r u c t i o n s g i v e n to Group I were read,, w i t h the f o l l o w i n g a d d i t i o n : One more t h i n g ; when I say "press down" p l e a s e p r e s s down bot h keys and keep them down u n t i l I t e l l you to r e s t your f i n g e r s . During t h i s time p l e a s e l o o k at the l i g h t and t r y not to move your head. At the end of each time we go through the twelve p a i r s you w i l l be g i v e n a chance to r e s t your f i n g e r s . OK? Then press down. The maze was presented i n the manner .outlined f o r Group I . The su b j e c t kept the buttons, pressed down and looked at the l i g h t c o n t i n u o u s l y throughout each t r i a l , and r e s t e d h i s f i n g e r s , d u r i n g the ten second pause between t r i a l s ' . A f t e r the s e s s i o n was completed each s u b j e c t was asked I f he had f e l t any f a t i g u e i n h i s f i n g e r s d u r i n g the experiment. No s u b j e c t r e p o r t e d any such f e e l i n g s o f f a t i g u e . GROUP I I I . Systematic Changes i n C o n d i t i o n s The procedure was i d e n t i c a l to t h a t of Group I I ( I n c l u d i n g the p r e l i m i n a r y t a s k ) , except f o r t r i a l s 3, 6, and 9. At the s t a r t of each of these t r i a l s the s u b j e c t was t o l d to stand up, p l a c e h i s hands on h i s hips., f a c e 90 degree's to the l e f t ("face the w a l l to your l e f t " ) of h i s o r i g i n a l 27 p o s i t i o n and t u r n h i s head back and l o o k a t the same l i g h t . The l i g h t was turned on du r i n g these t r i a l s by means o f the throw switch on the experimenter's t a b l e . The t r i a l s were conducted as usual,, except f o r the change of body posture. T r i a l s . 1 , 2 , . 1±, 7, and 8 were run e x a c t l y as those f o r Group I I . GROUP i y . R i g i d C o n t r o l P l u s Increased Accuracy of Recording Last-Made Responses Voeks ( 8 , p . 5 > 0 6 ) c l e a r l y s t a t e s that,, i f the response to the stimulus p a t t e r n of a ch o i c e p o i n t Is q o r r e c t , the l a s t -r ecorded response i s l i k e l y to be the last-made response. But i f the response i s i n c o r r e c t , then, when the s u b j e c t i s informed of t h i s , t h i s i n f o r m a t i o n w i l l o f t e n cause him to make other added responses (s u b - v o c a l l y i n the presen t experiment) to many of the, s t i m u l i p r e s e n t a t t h a t choice p o i n t . T h e r e f o r e , the last-made response i s o f t e n n ot the l a s t - r e c o r d e d response. T h i s w i l l make p r e d i c t i o n s based upon the l a s t - r e c o r d e d res-^ ponse o f t e n i n c o r r e c t . In order to.- remove t h i s d i f f i c u l t y , the f o u r t h group was t r e a t e d i n the same manner as the second ( r i g i d c o n t r o l ) group w i t h one added procedure. A f t e r each 'wrong 1 response by the subject,, the c h o i c e p o i n t was immediately repeated,, and the s u b j e c t gave the ' r i g h t ' response. The subjects, were informed ahead of time t h i s would happen and were prepared to c o r r e c t t h e i r responses when t h i s happened. No su b j e c t in- t h i s group f a i l e d to c o r r e c t h i m s e l f immediately 28 lie was. t o l d "wrong" and the p a i r o f l e t t e r s was repeated. In t h i s way the last-made response was always the 1 r i g h t 1 response and the r e c o r d i n g can he c o n s i d e r e d a c c u r a t e by Voeks* standards. In s p i t e o f the f a c t t h a t ( a c c o r d i n g to Voeks), t h i s group should show b e t t e r p o s t r e m i t y p r e d i c t i o n s > the r e s u l t s o f t h i s group i n r e l a t i o n to the other groups should be e v a l u a t e d w i t h caution-. I t i s obvious t h a t the p o s t r e m i t y p r e d i c t i o n s i n t h i s group w i l l always c o i n c i d e w i t h a p r e d i c t i o n o f the ' r i g h t * response. I t i s a l s o obvious t h a t t h i s group i s g e t t i n g more pr a c t i c e - on the maze and t h a t anyone would expect that, they would make a l a r g e r number of ' r i g h t 1 responses, than the o t h e r groups. The i n c i d e n c e o f more c o r r e c t r e s -ponses in' Group IV c o u l d be due to p o s t r e m i t y o p e r a t i n g * j u s t as the repeated * r i g h t * responses i n the oth e r groups c o u l d . But i t c o u l d a l s o be explained and p r e d i c t e d by a number of othe r concept's, and thus c o u l d h a r d l y be looked upon as evidence f o r po s t r e m i t y . Before t u r n i n g to the r e s u l t s o f the experiment, a b r i e f d i s c u s s i o n o f the r a t i o n a l e u n d e r l y i n g the. stimulus c o n t r o l s u t i l i z e d i n t h i s experiment i s i n order. To attempt to c o n t r o l i n t e r n a l arid p r o p r i o c e p t i v e s t i m u l i i s a d i f f i c u l t t a s k . I t is. probably now i m p o s s i b l e to do t h i s w i t h any h i g h degree of accuracy without 29 I n c a p a c i t a t i n g the. organism so b a d l y that h i s b e h a v i o r would be of l i t t l e use i n experiments, such as t h i s . A l l t h a t can be done Is to attempt to induce gross changes i n stimulus p a t -t e r n s . The methods employed i n the present experiment were used because Voeks had mentioned them s p e c i f i c a l l y as important or they were f e l t to be ' i n the s p i r i t ' o f h e r theory. Of course, w i t h t h i s type of gross c o n t r o l , i t can always be claimed t h a t the c o n t r o l was. not good enough i n some way> and t h a t t h i s i s r e s p o n s i b l e f o r the l a c k of r e s u l t s i n accordance w i t h a g i v e n t h e o r y . I n the present case.* f o r examplei> i t c o u l d be claimed that, the e f f e c t s o f f a t i g u e from p r e s s i n g the buttons produced marked changes, i n the s t i m u l u s s i t u a t i o n . o f the c o n t r o l group, so t h a t any d i f f e r e n c e s between i t and the 'change' groups would be e l i m i n a t e d . T h i s i s c e r t a i n l y p o s s i b l e , even though the s u b j e c t s f a i l e d to r e p o r t f a t i g u e . However, i t was f e l t t h a t any such e f f e c t s would pr o b a b l y not match the e f f e c t s of the pronounced p o s t u r a l changes. In Group I I I i n producing w i d e l y d i f f e r e n t stimulus, s i t u a t i o n s . The d i f f e r e n c e between Groups I and I I , and between I I and I I I were con s i d e r e d so extreme i n s t a b i l i t y of p r o p r i o c e p t i v e s t i m u l i t h a t i f Voeks i s c o r r e c t i n h e r t h e o r i z i n g the r e s u l t s should show, the e f f e c t s of these d i f -f e r e n c e s . One mqre point, here; the p r e l i m i n a r y t a s k (designed to l e s s e n the changing o f i n t e r n a l s t i m u l i ) was. i n c l u d e d In the t h i r d as w e l l as the second group (where i t -might appear that i t should not be i n c l u d e d , in. o r d e r to v a r y the s t i m u l i p a t t e r n ) because a d i f f e r e n c e between the two groups c o u l d e a s i l y be e x p l a i n e d away by warm-up e f f e c t s i f the t h i r d group- was. not admi n i s t e r e d the task . Thus the d i f f e r e n c e Could be e a s i l y e x p l a i n e d without- r e f e r e n c e to the p o s t r e m i t y h y p o t h e s i s . I t was co n s i d e r e d more a d v i s a b l e to equate the groups i n a l l . o ther r e s p e c t s , b e s i d e s the a c t u a l p o s t u r a l changes i n t r o d u c e d . The e f f e c t s of these p o s t u r a l changes then can be assumed to be the f a c t o r r e s p o n s i b l e f o r any d i f f e r e n c e s between the two groups. CHAPTER I I I THE DATA AND- THEIR TREATMENT The present chapter i s e n t i r e l y devoted t o the s t a t i s t i c a l a n a l y s i s o f the data. The d i s c u s s i o n of the i m p l i c a t i o n s of the r e s u l t s i s the s u b j e c t m atter of the next chapter. .For the comparison between the f q u r experimental groups, the responses on t r i a l s 3* 6, and 9 were analysed. These were the t r i a l s i n which systematic v a r i a t i o n of p r o -p r i o c e p t i v e s t i m u l a t i o n was. i n t r o d u c e d f o r Group I I I . I f d i f f e r e n c e s d i d r e s u l t because of this, v a r i a t i o n , they should be more ev i d e n t by a n a l y s i n g o n l y these three t r i a l s than e i g h t t r i a l s (the- f i r s t t r i a l has no p r e v i o u s responses to p r e d i c t from). F o r s c o r i n g , a response was counted as a c o r r e c t p o s t r e m i t y p r e d i c t i o n i f i t was the same response as was g i v e n on the l a s t t r i a l at the same choice p o i n t . F o r i n s t a n c e , I f the s u b j e c t had chosen, on t r i a l 5>, "N" at the c h o i c e P o i n t "N, J " , then a response of "N" on t r i a l s i x at- the same Choice p o i n t was counted as a c o r r e c t p o s t r e m i t y p r e d i c t i o n . F o r each s u b j e c t the number of c o r r e c t p r e d i c t i o n s were t o t a l l e d f o r each o f the t h r e e c r i t i c a l t r i a l s . In order to d e r i v e i n f o r m a t i o n about the r e l a t i v e e f f i c i e n c y o f the p o s t r e m i t y p r e d i c t i o n s n o t only between the " groups (methods) but a l s o between the three t r i a l s , , and also-i n f o r m a t i o n about the i n t e r a c t i o n o f these two> a s p e c i a l a p p l i c a t i o n of a n a l y s i s of v a r i a n c e d e s c r i b e d by Edwards (l,.p.288)i was used. T h i s technique allows, the t r i a l s to be c l a s s i f i e d i n one d i r e c t i o n and the experimental methods i n another. T h i s gave twelve separate subgroups of data, i n the p r e s e n t experiment. F o r each method the i n d i v i d u a l ' s scores, on t r i a l s 3> 6 and 9 are entered s e p a r a t e l y i n the appropriate, columns. I n t h i s way each su b j e c t has three scores In the table, o f a n a l y s i s . T h i s , of course, c r e a t e s a c o r r e l a t i o n of s c o r e s between t r i a l groups,, but not. between methods, where each subject e n t e r s only one method group. To- allow f o r t h i s c o r r e l a t i o n , a d i f f e r e n t e r r o r term, i s us.ed f o r the e v a l u a t i o n of the mean squares between methods than t h a t used f o r between t r i a l s . The s p e c i a l e r r o r term used f o r the e v a l u a t i o n of the: between t r i a l mean square, designed to take the. c o r r e l a t i o n of scores Into account, i s a l s o used to e v a l u a t e the t r i a l s and methods i n t e r a c t i o n ( a l s o i n f l u e n c e d by the c o r r e l a t i o n of s c o r e s ) ; Since the s c o r e s were p r o p o r t i o n s o f t o t a l p o s -s i b l e scores> the i n v e r s e sine o r angular t r a n s f o r m a t i o n was. used (i|.,p.l4lf9), i n an attempt to o b t a i n homogeneity o f v a r i a n c e s and n o r m a l i t y of the data. B a r t l e t f ' s t e s t of homogeneity of v a r i a n c e s was run f o r the twelve subgroups on the transformed scores. 33 The obtained c h i square of 9.895 was not s i g n i f i c a n t at the .05 l e v e l o f confidence where the c r i t i c a l v a lue i s 19.675 f o r eleven degrees of freedom. Homogeneity of v a r i a n c e s may, t h e r e f o r e , be assumed. The r e s u l t s o f the a n a l y s i s of v a r i a n c e are p r e -sented i n Table I . The obtained P r a t i o f o r d i f f e r e n c e s between methods (Groups I , I I , I I I , and IV i n the. experiment), Is 4..6.4, which i s s i g n i f i c a n t at the .0% l e v e l , o f c o n f i d e n c e . The obtained P r a t i o f o r d i f f e r e n c e s between t r i a l s , 71*9l|, i s s i g n i f i c a n t a t the .01 l e v e l o f confidence. The obtained P r a t i o f o r the i n t e r a c t i o n of t r i a l s and methods, was not s i g n i f i c a n t at the .05 l e v e l of c o n f i d e n c e . In o r d e r to determine where the d i f f e r e n c e s were between Groups I, I I , I I I , arid IV, the formuia':for the c r i t i c a l d i f f e r e n c e was used: V2 mean square w i t h i n The obtained v a l u e f o r d was 5*71 at the .05 l e v e l of confidence and 7~'57 a t the .01 l e v e l . Table I I shows the d i f f e r e n c e s between the means of the f o u r groups. These means are f o r s t o r e s on the three t r i a l s combined. As Table I I i n d i c a t e s , the s i g n i f i c a n t d i f f e r e n c e s between the means are between Group TV and each of the other three groups i n t u r n . Since Group IV has a l a r g e r mean than any of the other groups,, i t can be concluded t h a t Group IV had TABLE I RESULTS OF THE ANALYSIS OF VARIANCE OF THE NUMBER OF CORRECTLY PREDICTED RESPONSES ON TRIALS 3 , 6 , AND 9 Source of Varia t i o n Sums of Squares Degrees of Freedom Mean Squares F Between Methods 3604.78 3 1201.59 4 . 6 4 * Between Subjects i n the same Group 20717.38 80 258.97 Between T r i a l s 11367.97 2 5683.98 6 3 . 9 5 * Interaction: T r i a l s X Methods 895.35 6 149.23 1.68 Interaction: Pooled Subjects C T r i a l s 14221.10 160 Total 50806.58 251 * S i g n i f i c a n t at the .01 l e v e l of confidence TABLE I I DIFFERENCES BETWEEN THE MEANS 1 OF THE. FOUR GROUPS Mean I I I I I I I V I .98 2.20 . 7,^9* I I .1.22 8,47" I I I 9.69 a l g r i i f l e a n t at . 0f> l e v e l of confidence s i g n i f i c a n t at .01 l e v e l o f confidence The means and the c r i t i c a l d i f f e r e n c e were both com-puted from, transformed scores. The d i f f e r e n c e s r e p o r t e d i n t h i s t a b l e should hot be i n t e r p r e t e d a s percentages. T r a n s f o r m a t i o n o f these d i f f e r e n c e s back i n t o percentages would have- g i v e n meaningless, r e s u l t s , due to the nature of the o r i g i n a l t r a n s f o r m a t i o n . a s i g n i f i c a n t l y h i g h e r number of c o r r e c t p o s t r e m i t y p r e d i c t i o n s than each of the other three groups. I t can a l s o be concluded t h a t the Groups I , I I , and I I I do not d i f f e r s i g n i f i c a n t l y i n the number of c o r r e c t p o s t r e m i t y p r e d i c t i o n s . Since no i n t e r -a c t i o n e f f e c t was found s i g n i f i c a n t , i t can f u r t h e r be con-cluded t h a t these d i f f e r e n c e s and l a c k of d i f f e r e n c e s were s i m i l a r f o r each of the. t h r e e t r i a l s analysed, as w e l l as f o r the t o t a l of t h e three t r i a l s . When the mean scores (expressed i n the i n v e r s e sine form which was used f o r the analysis.) are converted back to percentages the. mean percentages f o r t h e - f o u r groups a r e : Group I , 79,3 per cent; Group I I 77.9 per cent; Group I I I , 76.2 per cent; Group IV, 88.8 per cent. These are the pe r -centages of responses on t r i a l s 3, 6, and 9 combined t h a t were c o r r e c t l y p r e d i c t e d by p o s t r e m i t y . To determine where the d i f f e r e n c e s were between t r i a l s 3, 6, and 9, the c r i t i c a l d i f f e r e n c e formula,, used above,, was not a p p l i c a b l e because of the c o r r e l a t i o n of scores between the three t r i a l s . I n s t e a d separate t - t e s t s were run, u s i n g the formula f o r p a i r e d cases: The obtained t f o r the comparison of t r i a l s 3 and 6 was 9.53 which was s i g n i f i c a n t a t the .001 l e v e l , o f conf i d e n c e 37 where the r e q u i r e d t f o r 83 degrees of freedom is. 3«J|2. Since t r i a l 6 had the l a r g e r mean score, i t f o l l o w s t h a t t r i a l 6 had s i g n i f i c a n t l y more c o r r e c t p o s t r e m i t y p r e d i c t i o n s than t r i a l 3« I n the same manner t r i a l 9 was found to have a l a r g e r number of c o r r e c t p o s t r e m i t y p r e d i c t i o n s than t r i a l 6. Here the obtained t value of 10.57 was s i g n i f i c a n t a l s o i n r e l a t i o n to the r e q u i r e d t v a l u e of 3 • ^4-2 at the .001 l e v e l o f c o n f i d e n c e . Since scores on t r i a l 6 were, found to be s i g n i f i c a n t l y h i g h e r than -on t r i a l 3, and scores, on t r i a l 9 s i g n i f i c a n t l y l a r g e r than those on t r i a l 6, no t - t e s t was needed to a s c e r t a i n that, scores on t r i a l 9 were a l s o s i g n i -f i c a n t l y l a r g e r than those on t r i a l 3« I n other words, the number of c o r r e c t p o s t r e m i t y p r e d i c t i o n s i n c r e a s e d s i g n i f i -c a n t l y from t r i a l 3 to t r i a l 6 to t r i a l 9 ,with the l a r g e s t number on t r i a l 9. When the mean scores are converted back to per-centages the mean percentages f o r the t h r e e t r i a l s a r e : t r i a l 3» 68.6 per dent; t r i a l 6,. 80.5 per cent; t r i a l 9, 90.9 per c e n t . Again, s i n c e the I n t e r a c t i o n o f t r i a l s and methods was not found to be s i g n i f i c a n t i n the a n a l y s i s of v a r i a n c e , i t can be concluded t h a t these r e s u l t s were s i m i l a r f o r each method as w e l l as f o r a l l the methods, t o t a l l e d . One more a n a l y s i s o f d i f f e r e n c e s between the experimental and C o n t r o l groups was c a r r i e d out. The l e v e l to which each s u b j e c t " l e a r n e d " was determined by t o t a l i n g 38 the number of ' r i g h t ' responses on the l a s t (9th) t r i a l . A s i n g l e c l a s s i f i c a t i o n analysis, of v a r i a n c e was. computed a f t e r a l l scores had been converted to angles, through the i n v e r s e sine t r a n s f o r m a t i o n . The obtained P r a t i o was 3.85, which was s i g n i f i c a n t at the .0$ l e v e l of confidence ( r e q u i r e d v a l u e = 2.72). The c r i t i c a l d i f f e r e n c e f ormula was Used and the d i f f e r e n c e s between the groups were found to be between Group TV, on the one hand, and each of the other t h r e e groups on the other. Since Group IV had a h i g h e r mean s c o r e , i t was concluded t h a t t h i s group had "learned 1* the maze to a h i g h e r c r i t e r i o n -of ' r i g h t ' responses. (Tables i n Appendix B.) When a l l the responses., Non the l a s t e i g h t of the nine t r i a l a , are examined f o r the e f f i c i e n c y of p o s t r e m i t y p r e d i c t i o n s , - Group I i s found to have 73 per cent o f I t s responses p r e d i c t e d c o r r e c t l y by p o s t r e m i t y . S i m i l a r r e s u l t s f o r the other groups were as f o l l o w s : Group II,. 72 per c e n t j Group I I I , 71 per Cent; and Group IV,. 83.2 per cent. The problem of the r e l a t i o n of p o s t r e m i t y p r e -d i c t i o n s w i t h simple p r e d i c t i o n s of the 'right?" response remains. Table I I I g i v e s the percentages, of c o r r e c t p o s t r e m i t y p r e d i c t i o n s , as quoted above, and the percentages of c o r r e c t ' r i g h t ? p r e d i c t i o n s . I t can be seen t h a t i n a l l the groups the two f i g u r e s are very s i m i l a r . I n Group IV they are n e c e s s a r i l y the same, si n c e the group was c o n t r o l l e d i n a way t h a t made the two p r i n c i p l e s p r e d i c t e x a c t l y the same i n a l l cases. I 39 TABLE I I I PERCENTAGES OF CORRECT PREDICTIONS BY POSTREMITY AND THE PERCENTAGE OF 'RIGHT* RESPONSES FOR EACH OF THE FOUR GROUPS Group I I I I I I IV P o s t r e m i t y 73 72 71 83 'Right-' 75 73 72 83 In the ot h e r three groups, when a product-moment c o r r e l a t i o n was computed between the number of ' r i g h t ' p r e -d i c t i o n s , and p o s t r e m i t y p r e d i c t i o n s f o r a l l 63 s u b j e c t s the obtained r was. .80. Though this- does not imply a n e c e s s a r y interdependence of the two p r e d i c t o r s , i t does indicate, that, the e f f i c i e n c y o f the two p r e d i c t o r s , i n a l a r g e measure,, v a r i e d t o g e t h e r between s u b j e c t s . R e f e r r i n g back to Table III. a g a i n * i t appears t h a t i n each of the thr e e groups where the two p r e d i c t o r s are not n e c e s s a r i l y equal i n e f f i c i e n c y , ' r i g h t * p r e d i c t i o n s were s l i g h t l y b e t t e r than p o s t r e m i t y p r e d i c t i o n s . The o n l y way a v a i l a b l e to analyse whether there is. a s i g n i f i c a n t , d i f f e r e n c e between the two was to 'separate' the two p r e d i c t o r s by con-s i d e r i n g o n l y those- responses- f o r which they p r e d i c t e d d i f -f e r e n t l y . I n doing this,, even more important r e s u l t s are obtained i n terms o f the hypotheses o f t h i s experiment. F o r , i n t h i s way,, the r e s u l t s o f p o s t r e m i t y p r e d i c t i o n s can be eval u a t e d , when the p r e d i c t i o n s do not c o i n c i d e w i t h p r e -d i c t i o n s o f the ' r i g h t ' response. For the 63 s u b j e c t s In Groups I , I I * and I I I , a t o t a l o f 1886 responses were recorded where the two p r i n c i p l e s d i s a g r e e d as - to the p r e d i c t e d r e s -ponse (out of a t o t a l number of responses, a f t e r t r i a l 1, of 6048). Of t h i s t o t a l (1886)> p o s t r e m i t y p r e d i c t e d 917 responses c o r r e c t l y , l e s s than h a l f . ('Right' p r e d i c t e d 9 6 9 responses c o r r e c t l y . ) So,, i t i s obvious t h a t p o s t r e m i t y i s no. b e t t e r a p r e d i c t o r than chance, here. I t i s important to note t h a t the two p r e d i c t o r s d i s a g r e e d o n l y when the postreme response (on the j u s t p r e v i o u s t r i a l ) was 'wrong'. I n t h i s case, p o s t r e m i t y would p r e d i c t a r e p e t i t i o n of the 'wrong' response and would d i s -agree w i t h the p r e d i c t i o n o f a ' r i g h t ' response made by the ot h e r p r e d i c t o r . I t f o l l o w s that, when p o s t r e m i t y p r e d i c t e d repeated 'wrong' responses i t operated no b e t t e r than chance. Th e r e f o r e , the s i g n i f i c a n t l y above-chance nature of p o s t r e m i t y p r e d i c t i o n s i n t h i s experiment must Come from p r e d i c t i o n s o f .repeated ' r i g h t ' responses. CHAPTER IV CONSIDERATION OP THE RESULTS IN RELATION TO THE HYPOTHESES TESTED" DISCUSSION Be f o r e s t a r t i n g a d i s c u s s i o n of the obtained r e s u l t s , I t is. worthwhile to r e - s t a t e the hypotheses, under t e s t : 1. P o s t r e m i t y w i l l be a b e t t e r p r e d i c t o r where the p r o p r i o c e p t i v e s t i m u l i a r e • h e l d c o n s t a n t than where they are s y s t e m a t i c a l l y v a r i e d o r l e f t to chance v a r i a t i o n , and w i l l be an even b e t t e r p r e d i c t o r where,, adde.d to a s t a b l e s t i m u l u s s i t u a t i o n , the r e c o r d i n g of 'last-made' responses i s more accurate than u s u a l . 2. P o s t r e m i t y w i l l be a b e t t e r - t h a n -chance p r e d i c t o r ( p o s s i b l y e x c l u d i n g the group where s t i m u l i are s y s t e m a t i c a l l y v a r i e d ) , and w i l l p r e d i c t b e t t e r than a simple p r e d i c t i o n of the ' r i g h t ' response; a l s o , p o s t r e m i t y ' s above-chance p r e d i c t i o n s w i l l not be e n t i r e l y dependent upon repeated ' r i g h t ' r e s p o n s e s . I n r e l a t i o n to the f i r s t h y p o t h e s i s , the r e s u l t s , of the a n a l y s i s of d i f f e r e n c e s between the experimental groups are p e r t i n e n t . The o n l y s i g n i f i c a n t d i f f e r e n c e s found were between Group IV and each of the other t h r e e groups. Thus the group (II) where the p r o p r i o c e p t i v e s t i m u l i were h e l d r e l a t i v e l y constant showed no b e t t e r postremi"cy p r e d i c t i o n s than the group ( I I I ) where the s t i m u l i were s y s t e m a t i c a l l y v a r i e d or the group (1) where the s t i m u l i were l e f t to chance v a r i a t i o n s . This, would appear to he. evidence a g a i n s t the p o s t r e m i t y h y p o t h e s i s , which would p r e d i c t d i f f e r e n c e s between these groups. The major q u a l i f i c a t i o n here would be t h a t t h i s con-c l u s i o n depends upon the assumption t h a t the methods employed i n d e a l i n g w i t h the.s.e groups a c t u a l l y d i d r e s u l t i n d i f f e r i n g degrees of stimulus s i t u a t i o n s t a b i l i t y , i n the ways d e s c r i b e d . In terms of Voeks,' t h e o r i z i n g , t h i s seems to be a r e l a t i v e l y safe assumption. No adequate t e s t of whether t h i s assumption was f u l f i l l e d i s possible,, of course. The o n l y course l e f t open f o r t e s t i n g p o s t r e m i t y i s to attempt to c o n t r o l the stimulus s i t u a t i o n i n the manner that the advocate of the p r i n c i p l e has h y p o t h e s i z e d important. This, was done i n the present experiment by employing many of the. same c o n t r o l s Used by Voeks h e r s e l f , and others, which seem to f o l l o w l o g i -c a l l y from her theory. There can be l i t t l e doubt t h a t the methods employed produced pronounced changes i n the p r o p r i o -c e p t i v e p a t t e r n of the s u b j e c t s i n the v a r y i n g stimulus, group. Voeks h e r s e l f has s t a t e d t h a t the u s u a l c o n t r o l s employed i n l e a r n i n g experiments cr e a t e the l i k e l i h o o d of s t i m u l u s v a r i a b i l i t y . Thus the group submitted to o n l y the l o o s e con-t r o l s a p p l i e d i n Group I can a l s o be assumed,. I f Voeks i s c o r r e c t , to have had v a r y i n g p r o p r i o c e p t i v e s t i m u l i . The q u e s t i o n t h a t remains i s whether the group t h a t was. r i g i d l y c o n t r o l l e d had s i g n i f i c a n t l y l e s s changes i n stimulus s i t -u a t i o n than these o t h e r tw.o groups. No d e f i n i t e answer i s p o s s i b l e . I t can o n l y be s t a t e d t h a t t h i s p r o b a b l y was the case. I f the r e s u l t s o f this, experiment are to be disc o u n t e d upon the re a s o n i n g t h a t this, was not the case, then i t would be n e c e s s a r y to r e s t a t e the c o n d i t i o n s under which s t i m u l i can be co n s i d e r e d to remain c o n s t a n t . As now s t a t e d , the p r i n c i p l e of p o s t r e m i t y was not supported i n i t s t h e o r e t i c a l a s p e c t s by t h i s experiment. The q u e s t i o n of the i n t e r p r e t a t i o n of the obtained h i g h e r r a t e o f p r e d i c t i o n s f o r the f o u r t h group remains. I n t h i s group the c o n d i t i o n s were so. manipulated t h a t the p o s t -r e m i t y p r e d i c t i o n was always the ' r i g h t ' response. I n t h i s way more accurate r e c o r d i n g o f last-made responses, was assured, i n Voeks' sense. Thus, she would p r e d i c t t h a t more of the p r a c t i c a l p o s t r e m i t y p r e d i c t i o n s would be c o r r e c t than where the r e c o r d -i n g was l e s s a c c u r a t e . However, as was p o i n t e d out i n Chapter IX, the p o s t r e m i t y p r e d i c t i o n s f o r t h i s group w i l l always be the ' r i g h t ' response*, s i n c e i t was assured t h a t the postreme response was ' r i g h t ' . A l s o , w i t h the a d d i t i o n a l p r a c t i c e t h a t t h i s group had on the maze, almost anyone would p r e d i c t t h at t h i s group would be making a l a r g e r number of ' r i g h t ' responses than the oth e r groups.. The i n c i d e n c e o f more ' r i g h t ' responses i n t h i s group than i n the other groups Could be e x p l a i n e d by p o s t r e m i t y ( s i n c e the postreme response was always ' r i g h t ' ) , -but the g r e a t e r number of repeated responses (and thus p o s t r e m i t y ' a h i g h p r e d i c t i v e r a t e ) c o u l d a l s o be e x p l a i n e d as. due to more p r a c t i c e . As a r e s u l t , the obtained d i f f e r e n c e s between Group IV and the oth e r groups can h a r d l y h e l d to be evidence which h e l p s support the p o s t r e m i t y p r i n c i p l e . The l a c k o f support f o r the t h e o r e t i c a l aspect o f pos t r e m i t y , i n the absence of the hypothesized' d i f f e r e n c e s between the f i r s t three groups, coupled w i t h the i n c o n c l u s i v e -ness o f the obtained d i f f e r e n c e s between Group IV and the other groups, c a s t s a good d e a l of doubt upon the t h e o r e t i c a l found-a t i o n o f po s t r e m i t y . The f a c t t h a t p o s t r e m i t y i s a p r a c t i c a l p r e d i c t o r of a h i g h order,, however, remains. I n the present experiment p o s t r e m i t y p r e d i c t e d c o r -r e c t l y a h i g h percentage o f the time f o r each one o f the f o u r groups employed. The p r e d i c t i v e a b i l i t y i n each group was s i g n i f i c a n t l y above chance. These r e s u l t s agree w i t h those of Voeks. F i v e r e s u l t s support the s u s p i c i o n , d i s c u s s e d e a r l i e r , t h a t c o r r e c t p r e d i c t i o n s by p o s t r e m i t y depend somehow on ' r i g h t ' responses.. 1 . The obtained r e s u l t s which i n d i c a t e t h a t s u c c e s s -f u l p r e d i c t i o n s i n c r e a s e d s i g n i f i c a n t l y from t r i a l s 3 to 6 to 9 agrees w i t h Waters.' and R e i t z ' a f i n d i n g s that s u c c e s s f u l p o s t r e m i t y p r e d i c t i o n s i n c r e a s e as ' r i g h t ' responses, are 46 i n c r e a s e d . 2. A l s o i n agreement w i t h t h i s f i n d i n g i s the f a c t that p o s t r e m i t y was a b e t t e r p r e d i c t o r i n the group (IV) which " l e a r n e d " the maze to the h i g h e s t c r i t e r i o n (gave more ' r i g h t * r e s p o n s e s ) . 3. The second p a r t of the second h y p o t h e s i s b e i n g t e s t e d i s not upheld by t h i s experiment. The p r e d i c t i o n o f a * r i g h t * response at each choice p o i n t proved as good, though no better., a p r e d i c t o r as p o s t r e m i t y . T h i s removes much of the a t t r a c t i v e n e s s , of p o s t r e m i t y as a p r a c t i c a l p r e -d i c t o r i n the maze s i t u a t i o n . F o r an even s i m p l e r p r i n c i p l e of p r e d i c t i o n is. as suaces.sful. 4- I t was noted i n the r e s u l t s t h a t not o n l y were p o s t r e m i t y p r e d i c t i o n s and * r i g h t ' p r e d i c t i o n s e q u a l l y good* but t h a t the product-moment c o r r e l a t i o n of the two, c o n s i d e r -i n g them f o r each subject,. Was h i g h (*80). These f o u r r e s u l t s l e a d to the p o s s i b l e s u s p i c i o n t h a t p o s t r e m i t y was somehow dependend upon repeated ' r i g h t ' responses f o r i t s h i g h p r e d i c t i o n r a t e . S>. The f i f t h r e s u l t e s t a b l i s h e d t h i s p o i n t con-4 c l u s i v e l y . A s e p a r a t i o n of the f o u r p o s s i b l e sequences of responses at any choice p o i n t from one t r i a l to the next, w i l l h e l p c l a r i f y this, d i s c u s s i o n . They a r e : 1) r i g h t - r i g h t ; 2) right-wrong; 3) wrong-wrong; and 4) wrong-right. In 1 and 2 p o s t r e m i t y p r e d i c t s repeated ' r i g h t * responses ( i t i s c o r -r e c t i n 1 and i n c o r r e c t i n 2). In 3 and 4 p o s t r e m i t y p r e d i c t s repeated 'wrong' responses ( i t i s c o r r e c t i n 3 and i n c o r r e c t i n ij.). I t was found i n the a n a l y s i s o f the r e s u l t s that, when po s t r e m i t y and ' r i g h t ' p r e d i c t i o n s d i s a g r e e d (3 and above p o s t r e m i t y p r e d i c t e d no b e t t e r than chance. That i s , repeated * wrong' responses, o c c u r r e d no more, f r e q u e n t l y than chance would p r e d i c t . Since p o s t r e m i t y i s c o r r e c t o n l y when e i t h e r a ' r i g h t ' or a 'wrong' response is. repeated, i t would appear t h a t the f a c t t h a t p o s t r e m i t y p r e d i c t s above chance i s e n t i r e l y due to i t s p r e d i c t i n g repeated ' r i g h t ' responses.. In other words, the r e s u l t s o f this, experiment support the hy p o t h e s i s t h a t p o s t r e m i t y i s o f no s i g n i f i c a n t p r e d i c t i v e value except when p r e d i c t i n g t h a t ' r i g h t ' responses w i l l be repeated. These remarks are of course l i m i t e d to m u l t i p l e T mazes,, where there i s o n l y one ' r i g h t ' and one 'wrong' response p o s s i b l e . When t h i s r e s u l t i s coupled w i t h f i n d i n g t h a t a p r e d i c t i o n o f the ' r i g h t ' response i s as good as a p r e d i c t i o n of the postreme response, the va l u e o f p o s t r e m i t y as a p r a c t i -c a l p r e d i c t o r i s c o n s i d e r a b l y d i m i n i s h e d . CONCLUSION I t was found t h a t the m a n i p u l a t i o n of the s t a b i l i t y of the stimulus, s i t u a t i o n produced no d i f f e r e n c e i n the r a t e of s u c c e s s f u l p o s t r e m i t y p r e d i c t i o n s . A l s o , i t was found t h a t a simpler p r i n c i p l e p r e d i c t e d as w e l l as p o s t r e m i t y , and t h a t p o s t r e m i t y performed above chance only when i t p r e d i c t e d 48 the ' r i g h t ? response would be repeated. T h e r e f o r e , the, s t a t u s of the concept of p o s t r e m i t y , as i t operates i n m u l t i p l e T mazes, i s c h a l l e n g e d by the r e s u l t s , of t h i s experiment. The observed d i f f e r e n c e s between Group IV and the o t h e r three groups* which h e r e t o f o r e l e d to ambiguous interr-p r e t a t i o n s , can now be seen to be b e t t e r e x p l a i n e d on the b a s i s of the i n c i d e n c e of ' r i g h t ' responses, than by a p o s t r e m i t y theory which i s not supported by t h i s experiment. CHAPTER V .SUMMARY The purpose of this, experiment was to i n v e s t i g a t e the v a l i d i t y o f the p o s t r e m i t y p r i n c i p l e . T h i s p r i n c i p l e predicts., f o r r e c u r r i n g s i t u a t i o n s , t h a t the next response made w i l l he the same re.sponse l a s t made to the s t i m u l i p r e s e n t . I t was noted t h a t t h i s p r i n c i p l e emphasizes the importance of s t a b l e stimulus, s i t u a t i o n s , e s p e c i a l l y of pror-p r i o c e p t i v e s t i m u l i , i n making s u c c e s s f u l p r e d i c t i o n s . The hypotheses under t e s t were, concerned w i t h the e f f e c t s of v a r y i n g the s t a b i l i t y o f p r o p r i o c e p t i v e s t i m u l i upon s u c c e s s f u l p o s t r e m i t y predictionsi,- and the p o s s i b l e dependency of s u c c e s s f u l p r e d i c t i o n s upon ' r i g h t 1 responses by the s u b j e c t s . The l e a r n i n g s i t u a t i o n used i n t h i s experiment to o b t a i n responses was a mental maze. There were twelve- choice p o i n t s i n the maze, each one w i t h one ' r i g h t * c h o ice and one 'wrong' choice p o s s i b l e . Each s u b j e c t was run through the maze n i n e times. The methods used to c o n t r o l s t a b i l i t y o f p r o p r i o -c e p t i v e s t i m u l i c o n s i s t e d l a r g e l y of c o n t r o l of motor r e s -ponses and po s t u r e . In one group r e l a t i v e l y l i t t l e c o n t r o l of motor responses, o r posture was. e x e r c i s e d , while, i n another group the motor responses and the posture of the s u b j e c t were h e l d constant. I n a t h i r d group the s t i m u l i were v a r i e d on c e r t a i n t r i a l s . . A f o u r t h group had, i n a d d i t i o n to s t i m u l u s constancy, any c h o i c e p o i n t t h a t e l i c i t e d a 'wrong' response repeated immediately, so t h a t the s u b j e c t c o r r e c t e d h i s r e s -ponse. This. was. done to g a i n more accurate r e c o r d i n g of responses, which was h y p o t h e s i z e d as b e i n g v e r y d i f f i c u l t when the l a s t response i s 'wrong'. The a n a l y s i s of the r e s u l t s i n d i c a t e d d i f f e r e n c e s i n the number of s u c c e s s f u l p r e d i c t i o n s o n l y between the f o u r t h group (repeated choice p o i n t s ) , on the one hand, and each o f the o t h e r three groups, on the other hand. Thus, no d i f f e r -ences were found between the three groups where o n l y s t a b i l i t y of p r o p r i o c e p t i v e s t i m u l i v a r i e d . F u r t h e r a n a l y s i s i n d i c a t e d p o s t r e m i t y was a s u c c e s s -f u l p r e d i c t o r o n l y when i t p r e d i c t e d a ' r i g h t ' response. I n r e l a t i o n to t h i s f i n d i n g , a simple p r e d i c t i o n o f the . ' r i g h t ' response at each choice p o i n t proved as e f f i c i e n t as. p o s t -remity. The r e s u l t s l e d to the c o n c l u s i o n t h a t the o b t a i n e d difference's i n the number of s u c c e s s f u l p r e d i c t i o n s between Group XV and the o t h e r three groups was due to the i n c i d e n c e of more ' r i g h t ' responses i n t h i s group- (which had more p r a c t i c e ) . Thus the r e s u l t s of t h i s experiment d i d not sup-p o r t the hypothesized importance o f stimulus s t a b i l i t y f o r p o s t r e m i t y , and a l s o p r o v i d e d an a n a l y s i s which showed i t s s u c c e s s f u l p r e d i c t i o n s were c o i n c i d e n t w i t h r e p e t i t i o n of ' r i g h t ' responses. T h i s r e p e t i t i o n of ' r i g h t 1 responses could be p r e d i c t e d by many t h e o r i e s . The v a l i d i t y of p o s t r e m i t y as a p r a c t i c a l p r e d i c t o r and as a t h e o r e t i c a l concept was, w i t h i n the l i m i t a t i o n s of t h i s experiment*, questioned. 52 BIBLIOGRAPHY 1. Edwards, A.L. Experimental Design i n Psychological Research. New York: Rinehart, 1950. ~~ 2. Guthrie, E.R. The Psychology of Learning (rey. ed.). New York: Harper, 1952. 3« Osgood, G.E. Method and Theory i n Experimental Psychology. New York: Oxford University Press, 1953. 1+. Peterson, J . Learning when frequency and recency factors are negative. J . Exp. Psychol.< 1922, 5, 270-300. 5. Snedecor, G.W. S t a t i s t i c a l Methods. Ames, Iowa: Collegiate Press, 191|.6. 6. Waters., R.H. and Reitz, J.G. The role of recency i n learn -ing. J . Exp, Psychol.. 1950, 1+0, 251+-259. 7. Voeks,. V.W. Acq u i s i t i o n of S-R connections: a tes t of Hull's and Guthrie's Theories. J . Exp. Psychol-., 1954, k7r 137-1V7.• 8. Voeks, V.W. Postremity, Recency, and Frequency. J . Exp. Psychol.. 19l)-8, 38,. 1+95-51.0. APPENDIX A THE MENTAL MAZE Choice P o i n t 1 2 3 ^ 5 6 7 8 9 10 11 12 1st L e t t e r N U* T* P S Y* M E V* R* I 2nd L e t t e r J * L A 0* B D* 0 K* W* H P G* APPENDIX B RESULTS OP THE ANALYSIS OP VARIANCE OF THE NUMBER OF 'RIGHT' RESPONSES ON TRIAL 9 Source o f V a r i a t i o n Sums Degrees Mean F of of squares squares freedom Between Groups 2078.53 3 692.84 3.85* W i t h i n Groups 14384.15 80 179.80 s i g n i f i c a n t a t the .05 l e v e l of confidence DIFFERENCES BETWEEN THE MEANS OF THE "POUR GROUPS Mean I I I H I Iv I 2.87 5.84 8.57* I I 2.97 10.44* I I I 13.41.. w s i g n i f i c a n t at the .05 l e v e l of confidence s i g n i f i c a n t a t the .01 l e v e l o f confidence 

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