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Effect of perceptual learning upon disappearances of luminous figures More, Linda Kathleen 1967

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EFFECT OF PERCEPTUAL LEARNING UPON DISAPPEARANCES OF LUMINOUS FIGURES by LINDA KATHLEEN MORE B.A., University of B r i t i s h Columbia, 1965 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS in the Department of Psychology We accept t h i s t h e s i s as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1967 In p re sen t i ng 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 .idvanced 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 th;.; L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study I f u r t h e r agree that permiss ion f o r ex ten s i ve 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 representat ives. . It 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 a l lowed wi tliout my w r i t t e n permission.. Department of VQKCHOLOQf The U n i v e r s i t y o f B r i t i s h Columbia Vancouver 8, Canada D a t e A P R I L Qjo \3(ol. i ABSTRACT Perceptual learning was studied using luminous figures i n a dark room. I t was found that as a r e s u l t of previous close temporal and s p a t i a l concurrence, discriminably d i f -ferent s t i m u l i under reduced stimulation conditions disappear together more frequently than without such an association. This occurred despite a demonstrated l i n k between i d e n t i c a l s t i m u l i p r i o r to the learning experience. Moreover i t was shown that the extent to which the s t i m u l i subsequently "operated" together was a function of the frequency and duration of t h e i r previous j o i n t occurrence. Temporal and s p a t i a l stimulus-stimulus rel a t i o n s h i p s were manipulated and differences between sequential and simultaneous presenta-tions and between d i f f e r e n t presentation rates were observed and discussed. The e f f e c t of auditory experience on sub-sequent disappearances of the same s t i m u l i presented v i s u a l l y was also examined and the r e s u l t s supported the inter-modal perceptual learning hypothesis. The phenomena observed i n a l l these experiments were interpreted i n terms of Hebb's theory of perceptual association. i i Table of Contents Abstract i L i s t of Tables i i i L i s t of Figures v Acknowledgment v i Introduction 1 Method and Results Experiment I Amount of Perceptual Learning A. Number of Repeated Exposures to a Stimulus 8 B. Time of Exposure to Test Target 17 C. Number and Duration of Exposures to Training S t i m u l i 20 Experiment II Temporal and S p a t i a l Relations.... 26 Experiment I I I Auditory Perceptual Learning .... 32 Discussion 39 References 49 Appendix 53 i i i L i s t of Tables I Analysis of Variance f o r "Other" Pair Dis-appearances i n Experiment I A 12 II Analysis of Variance for Proportions of Training-Pair Disappearances i n Experiment I A 13 III Tests of Significance for Mean Differences i n Training-Pair Proportions Before and After Perceptual Learning 14 IV Tests of Significance for Mean Differences i n Net Proportions of Training-Pair Disappearances Between Learning Conditions In Experiment I A 15 V Analysis of Variance for Proportions of Identical-Pair Disappearances for D i f f e r e n t Observation Sessions i n Experiment I B 18 VI Tests of Significance of Changes i n Proportions of I d e n t i c a l - P a i r Disappearances for D i f f e r e n t Observation Sessions 19 VII Analysis of Variance for Proportions of Tr a i n -ing-Pair Disappearances i n Experiment I C 24 VIII Test f o r Significance of Mean Difference i n Proportions of Paired Disappearances With and Without Training 25 IX Tests for Significance of Differences i n Mean Difference Proportions of Training-Pair Dis-appearances Between Training-Condition Groups .. 26 X Analysis of Variance for Proportions of Training-Pair Disappearances i n Experiment II 29 i v XI Tests of Significance of Differences i n Mean Proportions of Paired Disappearances With and Without Training 30 XII Analysis of Variance for Proportions of Training-Pair Disappearances i n Experiment I I I 34 XIII Tests for Significance of Mean Difference i n Proportion of Disappearances With and Without Training 35 XIV Binomial Tests for To t a l Proportions of Identical-Pair Disappearances i n Targets Without Training for A l l Experiments 37 XV ^  Numbers and Proportions of Disappearances for the Two Luminous Targets i n Experiment I A .... 54 XVI Binomial Tests of Disappearances of Ide n t i c a l Pairs i n Targets Without Training 56 XVII Changes i n Proportions of Iden t i c a l - P a i r Disappearances Over Time, Experiment I B 62 XVIII Frequencies and Proportions of Disappearances i n Three Targets, Experiment I C 63 XIX Frequencies and Proportions of Paired Dis-appearances With and Without Training, Experiment I C 64 XX Numbers and Proportions of Paired Disap-pearances With and Without Perceptual Ex-perience, Experiment II 66 XXI Frequencies and Proportions of Paired Disap-pearances With and Without Auditory Perceptual Experience 68 L i s t o f F i g u r e s B i n e a r t r e n d o f mean d i f f e r e n c e s i n p r o -p o r t i o n s o f t r a i n i n g - p a i r d i s a p p e a r a n c e s b e f o r e and a f t e r p e r c e p t u a l l e a r n i n g , as a f u n c t i o n o f the number o f exposure p a i r i n g s v i Acknowle dgme n t The a u t h o r w i s h e s t o acknowledge the h e l p , p r o d d i n g and c r i t i c i s m o f Dr. R i c h a r d C. Tees i n the r e s e a r c h and w r i t i n g o f t h i s p a p e r . 1 Perceptual learning may ref e r to the fac t that percep-t i o n i t s e l f depends on experience, or to the proposition that learning i s a process c l o s e l y r e l a t e d to perception and consisting of a reorganization or integration of e x i s t i n g perceptual processes. That perception depends on experience i s demonstrated by the impairment of perceptual a b i l i t y a f t e r experience with the environment has been prevented. Sensory deprivation studies with animals (Siegel, 1953; Riesen, 1961; Nissen, Chow and Semmes, 1951) and c l i n i c a l data on adult cataract patients whose v i s i o n had been restored by s u r g i c a l operation (von Senden, 1932) strongly suggest that at le a s t some aspects of perception are acquired through learning. In support of the hypothesis that learning involves a re-organization of perceptual processes, i t has been shown that experience with s t i m u l i makes the organism more capable of dealing with these s t i m u l i i n subsequent s i t u a t i o n s . Gibson and Walk (1956) r a i s e d rats from b i r t h i n cages i n which the walls e i t h e r were p l a i n white or contained two t r i a n g l e s and two c i r c l e s . A f t e r three months the animals were given a discrimination task involving a c i r c l e and a t r i a n g l e . The 2 patterned-cage group performed consistently better. In a l a t e r experiment (Gibson, Walk, Pick, Tighe, 1958) the ex-posure was to an e q u i l a t e r a l t r i a n g l e and a c i r c l e and the discrimination tests involved an isosceles t r i a n g l e and an e l l i p s e . Performance of the experimental subjects was again superior to that of the controls. A further t e s t was con-ducted using s t i m u l i markedly d i f f e r e n t from the o r i g i n a l exposure s t i m u l i with r e s u l t s favourable to a s p e c i f i c exposure-pattern i n t e r p r e t a t i o n rather than a general free-environment explanation. Enrichment-type studies done with humans give si m i l a r r e s u l t s . Donderi and Kane (1965) gave subjects c o n t r o l l e d perceptual learning experience. The subjects learned to give a common response " A " to two d i f f e r e n t c i r c l e s and another response "B"; to a t h i r d c i r c l e . The experimenters found that the common-response p a i r of s t i m u l i subsequently operated together i n a t e s t s i t u a t i o n more frequently than any other p a i r . In another part of the experiment they found that recognition t r a i n i n g had the same e f f e c t . One further type of evidence used to support the existence of perceptual learning has been gathered under s t a b i l i z e d image conditions. Several techniques have been 3 used which seem to give comparable data: p a r t i a l s t a b i l i z a -t i o n of r e t i n a l images, or "stimulus induced" s t a b i l i z a t i o n i n which figures (often luminous) are observed under reduced stimulation conditions. The fundamental observation i s the r a p i d disappearance (and reappearance) of simple v i s u a l ob-j e c t s . Using a r e t i n a l s t a b i l i z a t i o n technique, Pritchard, Heron and Hebb (1960) found that v i s u a l targets fragmented and regenerated i n meaningful units; McKinney (1963) got equiva-lent data using luminous figures. Pritchard (1961) reported that meaningless curl i c u e s f i r s t appeared and disappeared i n random sequence, but a f t e r a while small groups of curlicues organized i n recognizable patterns started to behave as units, suggesting that they had themselves become meaningful per-ceptual elements. Hart (1964) suggested that meaningful d i s -appearances are produced i n d i r e c t l y by the meaningful manner i n which the subject f i x a t e s on the t e s t f i g u r e . McKinney (1964) argued that Hart's r e s u l t s depended on the fact that h i s figures impinged almost e x c l u s i v e l y on the fovea, the r e t i n a l area l e a s t sensitive to l i g h t , and he demonstrated that the disappearance of a large target does occur i n a per-ceptually organized manner. McKinney*s data were further sup-ported i n research done by Schuck, Brock, and Becker (1964). 4 Schuck and Leahy (1966), however, suggested that response bias rather than perceptual organization might be responsible for the preponderance of meaningful disappearances noted i n previous research. McKinney (1966) concluded that perception i s enhanced by the meaningfulness of the target because of both the greater a b i l i t y f or verbal mediation and the greater frequency of previous presentations. Many of these findings have been used to support an association theory of perceptual learning (Hebb, 1949). Ac-cording to t h i s theory of perception the learning occurs through the development of complex neural loops ( c e l l as-semblies) i n the cortex, by r e p e t i t i v e stimulation. When active together these loops develop i n t e r f a c i l i t a t i o n , sup-porting one another's action, and plustse sequences are formed. P a r t i a l s t a b i l i z a t i o n produces adaptation, which reduces stimulus input to the c e n t r a l nervous system. The disap-pearance phenomenon i n p a r t i a l s t a b i l i z a t i o n i s att r i b u t e d by Hebb (1963) to the i n h i b i t i o n of an enti r e phase sequence, r e s u l t i n g from a drop of stimulus input below the value neces-sary to overcome c e l l r e fractory periods. The perceptual phenomena observed with reduced stimulation conditions sug-gest the same explanation i n terms of ce n t r a l processes. 5 Research by Clarke and Evans (1962, 1964, 1965) supports the proposition that c e n t r a l processes are involved. According to them the e f f e c t i s not i n the primary receptors, but may be at the L.G.N, or cortex. I f c e n t r a l process i n h i b i t i o n i s responsible f o r d i s -appearances experienced under reduced stimulation conditions and during r e t i n a l s t a b i l i z a t i o n , and i f the development of these neural processes i s dependent upon perceptual learning, then experience should influence subsequent disappearances. To examine t h i s hypothesis, a perceptual learning exercise must be devised that can serve as a basis for predictions about l a t e r disappearances. The perceptual learning experience employed i n t h i s experiment was based on a method used by Deitcher (1957), Tees (1960) and others for studying the nature of immediate memory. Their subjects were asked to attempt to repeat series of d i g i t s , supposedly to see whether practice i n the r e p e t i t i o n would improve performance. A c t u a l l y every t h i r d set of d i g i t s was the same, and the r e a l problem was to f i n d out whether t h i s p a r t i c u l a r series would be learned and remembered. It was shown that cumulative learning d i d occur. This task was modified i n the present experiment to eliminate the relevance of the observer's verbal responses 6 and r e s t r i c t experience to S-S associations, i n order to get a co n t r o l l e d learning experience i n which perceptual learning might be examined to a c e r t a i n extent independently of atten-t i o n and response t r a i n i n g . A reduced stimulation technique for investigating per-ceptual learning was used i n these experiments. They were de-signed to examine the proposition that close temporal and s p a t i a l concurrence of discriminably d i f f e r e n t s t i m u l i could cause these s t i m u l i to subsequently disappear together more frequently than without such an association. Whether the s t i m u l i subsequently "behave" together as a function of t h e i r previous j o i n t occurrence was also to be examined. Subse-quently, both the frequency and the duration of exposure to the s t i m u l i were manipulated to discover t h e i r e f f e c t on the strength of the perceptual association. The effectiveness of simultaneous and sequential presentation of s t i m u l i i n the perceptual learning s i t u a t i o n were then compared. Another experiment was performed to investigate whether the temporal and s p a t i a l relationships between s t i m u l i might further a f f e c t the strength of the perceptual association between these s t i m u l i . A f i n a l i n v e s t i g a t i o n was c a r r i e d out to determine whether auditory experience with s t i m u l i would produce 7 predictable changes in disappearances of these same stimuli presented visually. Whether temporal relationships between the auditory stimuli might influence the effectiveness of the visual S-S associations was also studied. 8 EXPERIMENT I Amount of Perceptual Learning: A. Number of Repeated Exposures to a Stimulus To investigate the e f f e c t of p r i o r experience on per-ceptual phenomena, disappearances of luminous figures before and a f t e r a perceptual learning experience were compared. Attention and response t r a i n i n g were co n t r o l l e d by having two post-learning t e s t targets, one of which had not been previously viewed, and by having the subjects perform an i r r e l e v a n t task during the learning period. The t r a i n i n g consisted of re-peated presentations of c e r t a i n stimulus-pairs. In t h i s ex-periment, the number of presentations was varied to discover whether the greater the frequency of pairings, the greater would be the proportion of subsequent concurrent disappearances of the p a i r under reduced stimulation conditions. Method Subjects The Ss were 50 college student volunteers. Ten Ss were randomly assigned to each of f i v e perceptual learning conditions. 9 Pre-Learning Test The s t i m u l i were two luminous t h r e e - d i g i t targets ( 8 5 5 and 332) . These figures were chosen because they com-bined s t r a i g h t and curved l i n e s . The h o r i z o n t a l l y arranged 1 d i t i s were 3 i n . high and 3 i n . thick, equidistant from each i other. At the 5 z f t . viewing distance, each d i g i t subtended a v i s u a l angle of 2.7 degrees. A l l three d i g i t s subtended an angle of 6.1 degrees. In a darkened, light-proof room, each S_ viewed only one of the targets, monocularly with the r i g h t eye for 5 min. The S_ was asked to fi x a t e on the center of the target, to attempt to keep head and eye fixed, to avoid un-necessary b l i n k i n g , and to report a l l complete-digit disap-pearances. Five randomly assigned Ss from each of the f i v e conditions were exposed to the target 8 5 5 , the remainder to 332. Perceptual Learning Experience The display materials were 2 x 2 i n . s l i d e s projected onto a 8 x 11 z i n . ground glass screen. Each s l i d e con-tained 2 to 9 d i g i t s h o r i z o n t a l l y arranged and was auto-m a t i c a l l y presented by a Kodak Carousel projector for 5 sec. With the S_ s i t t i n g 2 f t . from the screen, the s t i m u l i subtended 10 v i s u a l angles of 3.8 to 17.0 degrees. (Each d i g i t subtended an angle of 2.8 degrees.) Under conditions of low background illumination, the S_ f i x a t e d on the screen monocularly with the r i g h t eye and was asked to report the t o t a l number of d i g i t s i n each display. The t r a i n i n g s t i m u l i , the d i g i t p a i r s 32 and 85, were each embedded 0, 30, 45, 60 or 7 5 times i n the 100-slide presentation to which each S_ was exposed. For any i n d i v i d u a l S_ both d i g i t s were embedded the same number of times. Ten Ss were randomly assigned to each of the stimulus exposure condi-t i o n s . Post-Learning Test After the 100 s l i d e s the S_ returned to the pre-learning t e s t s i t u a t i o n described above, and the room was re-darkened. A l l Ss viewed both t h r e e - d i g i t targets i n the post-learning te s t for 5 min. each and again were asked to report complete-d i g i t disappearances. The target to which they had not previously been exposed was shown f i r s t . Results The r e s u l t s concerning t r a i n i n g p a i r disappearances for 11 the two targets are presented i n Table XV, i n the appendix. The reports of i n d i v i d u a l S_s were divided i n t o disappearances rel a t e d to " i d e n t i c a l " and " t r a i n i n g " stimulus-pairs. (Pro-portion of i d e n t i c a l - p a i r disappearances f o r an i n d i v i d u a l S_ may be determined by subtracting the t r a i n i n g - p a i r proportions from 1.000.) The disappearance of e i t h e r the d i g i t - p a i r (e.g. -55) or the odd d i g i t (e.g. 8—) i s evidence f o r the e f f e c t of an association between i d e n t i c a l d i g i t s on an i n -dividual's perception. The disappearance of the t r a i n i n g stimulus-pair (e.g. 85-) or the remaining d i g i t (e.g. —5) i s evidence for an association between the t r a i n i n g p a i r s . Disappearances of a l l d i g i t s simultaneously cannot be att r i b u t e d to a p a r t i c u l a r p a i r of d i g i t s and are not included i n the table. The disappearance of the center d i g i t s (e.g. 8-5) and the two outside d i g i t s (e.g. -5-) are also not reported. These appear to be r e l a t e d to f i x a t i o n on the center d i g i t rather than to an association between the outside s t i m u l i . This i s suggested by the preponderance of c e n t e r - d i g i t d i s -appearances (698) compared with disappearances of the outside d i g i t s (129) and supported by the i n s i g n i f i c a n t differences i n the disappearances of t h i s p a i r before and a f t e r perceptual learning (see Table I) . 12 Table I. Analysis of Variance f o r "Other" Pair Disappearances i n Experiment IA Source of V a r i a t i o n Sum of Squares df Mean Square F Between Subjects 1208.69 49 A (Learning Condition) 446.54 4 111.64 6.59* Subjects within groups 762.15 45 16.94 Within Subjects 1499.50 50 B (Before-After) 10.89 1 10.89 < 1.0 AB Interaction 6.86 4 1.72 < 1.0 B X Subjects within 1481.75 45 32.92 groups * s i g n i f i c a n t at p < 0.01 To show that the proportions of i d e n t i c a l - p a i r disap-pearances before the perceptual learning experience were s i g -n i f i c a n t l y d i f f e r e n t from chance, binomial tests were performed for each i n d i v i d u a l subject. These tests are presented i n Table XVI, i n the appendix. Identical p a i r s did disappear and appear together s i g n i f i c a n t l y more often than other p a i r s for most subjects. In order to determine whether or not any s i g n i f i c a n t 13 differences existed i n pre-learningstraining-pair disappearances for the f i v e exposure conditions, a one-way Analysis of Variance of the pre-learning scores was performed. The obtained F r a t i o (F=0.49; df 4,45) did not lead to r e j e c t i o n of the n u l l hy-pothesis. A two-factor Analysis of Variance on repeated measures (Winer, 1962) was made for the proportions of t r a i n i n g - p a i r disappearances. The re s u l t s are summarized i n Table I I . Table I I . Analysis of Variance for Proportions of Training-Pair Disappearances i n Experiment I A Sum of Mean Source of V a r i a t i o n Squares df Square F Between Subjects 3.21 49 A (Learning Condition) 1.33 4 0.332 7.90* Subjects within groups 1.88 45 0.042 Within Subjects 5.24 50 B (Before-After) 2.71 1 2.71 104.2 * AB Interaction 1.37 4 0.34 13.07* B X Subjects within groups 1.16 45 0.026 *p< 0.01 14 Since a s i g n i f i c a n t F r a t i o for the before-after com-parison was found, appropriate t tests were made to t e s t the hypothesis that the differences i n proportions between pre-and post-learning were due to chance (Ferguson, 1959). The re s u l t s of these t tests are displayed i n Table III and sup-port the perceptual learning hypothesis. A s i g n i f i c a n t i n -crease i n the proportions of disappearances d i d occur for the tr a i n i n g p a i r s (85 and 32) at 45, 60 and 75 exposures. Ap-parently the 30 paired exposures were not s u f f i c i e n t to produce evidence of perceptual learning i n t h i s s i t u a t i o n . Table I I I . Tests of Significance for Mean Differences i n Training-Pair Proportions Before and After Perceptual Learning (Target A) Training Condition 0 30 45 60 75 Mean Difference Target A 0.048 0.114 0.294 0.550 0.644 Target B 0.033 0.208 0.393 0.599 0.649 Target A 0.67 1.58 4.08* 7.64* 8.94* * p< 0.01 / These proportions are differences between Target A (before) and Target B ' ( a f t e r ) . 15 T e s t s were a l s o p e r f o r m e d t o compare the mean d i f f e r e n c e s between l e a r n i n g c o n d i t i o n s . The r e s u l t s o f t h e s e comparisons are summarized i n T a b l e IV. T a b l e I V . T e s t s o f S i g n i f i c a n c e f o r Mean D i f f e r e n c e s i n Net P r o p o r t i o n s o f T r a i n i n g - P a i r D i s a p p e a r a n c e s Between L e a r n i n g C o n d i t i o n s i n E x p e r i m e n t I A ( T a r g e t A) L e a r n i n g C o n d i t i o n s Mean D i f f e r e n c e t 0 and 30 0.066 0.72 0 and 45 0.246 2.67* 0 and 60 0.502 5.46** 0 and 75 0.596 6.48** * p <L 0.05 ** p < 0.01 In order to determine whether or not disappearance pro-portions were l i n e a r l y r e l a t e d to the exposure frequencies of the perceptual learning experience, trend analysis was c a r r i e d out (Edwards, 1960). A highly s i g n i f i c a n t r e s u l t was obtained (F=53114| df 1,45) which l e d to the conclusion that there was a', yeicvr- s i g n i f i c a n t l i n e a r trend i n the data (see Figure 1 ) . 16 F R E Q U E N C Y OF T R A I N I N G P A I R I N G S F i g u r e 1. L i n e a r t r e n d o f mean d i f f e r e n c e s i n p r o p o r t i o n s o f t r a i n i n g - p a i r d i s a p p e a r a n c e s b e f o r e and a f t e r p e r c e p t u a l l e a r n i n g , as a f u n c t i o n o f the number o f e x posure p a i r i n g s . 17 Amount of Perceptual Learning: B. Time of Exposure to Test Target In Experiment I A, two targets were viewed i n the post-learning t e s t . Evidence of perceptual learning with the previously unexposed target was even greater than with the target which was viewed both before and a f t e r t r a i n i n g . Experi-ment I B was performed to investigate whether repeated exposure to a target i n the pre-learning t e s t would increase the pro-portion of concurrent disappearances for the p a i r of s t i m u l i which i n i t i a l l y disappeared together most frequently. Method Subjects The Ss were 10 college student volunteers. Perceptual Learning Experience The luminous t h r e e - d i g i t target 332 was used i n t h i s experiment. Each S_ viewed the target for 5 min. as before and reported a l l complete-digit disappearances. Each S then viewed s l i d e s of 2 to 9 d i g i t s (which did not contain e i t h e r 3 or 2) for 5 min. f again reporting the t o t a l number of d i g i t s i n 18 each d i s p l a y . The Ss were t h e n r e t e s t e d f o r 5 min. w i t h t h e luminous t a r g e t 332. F i n a l l y one f u r t h e r 5 minute s l i d e p r e s e n t a t i o n and 5 minute r e t e s t w i t h the luminous t a r g e t oc-c u r r e d . R e s u l t s The r e s u l t s c o n c e r n i n g p a i r e d d i s a p p e a r a n c e s over the t h r e e o b s e r v a t i o n a l s e s s i o n s are p r e s e n t e d i n T a b l e X V I I i n the a p p e n d i x . An A n a l y s i s o f V a r i a n c e f o r p r o p o r t i o n s o f i d e n t i c a l -p a i r d i s a p p e a r a n c e s f o r the t h r e e s e s s i o n s was p e r f o r m e d and i s summarized i n T a b l e V. T a b l e V. A n a l y s i s o f V a r i a n c e f o r P r o p o r t i o n s o f I d e n t i c a l -P a i r D i s a p p e a r a n c e s f o r D i f f e r e n t O b s e r v a t i o n S e s -s i o n s i n E x p e r i m e n t I B Source o f V a r i a t i o n Sum o f Squares d f Mean Square F Between S u b j e c t s .54 9 .060 W i t h i n S u b j e c t s .73 20 .036 Between Treatments .25 2 .125 4.63* R e s i d u a l .48 18 .027 *p ^ 0.05 19 Since the F r a t i o was s i g n i f i c a n t , the proposition that s i g -n i f i c a n t changes occurred i n the proportions of i d e n t i c a l - p a i r disappearances over the three sessions was further examined by ca l c u l a t i n g t values f o r the differences between observation-session means. The r e s u l t s of these t tests are displayed i n Table VI. The mean differences between sessions 1 and 2 and between 2 and 3 are not s i g n i f i c a n t . The difference between sessions 1 and 3, however, does reach significance (p < 0.05). Table VI. Tests of Significance of Changes i n Proportions of Identical-Pair Disappearances for D i f f e r e n t Observa-t i o n Sessions i n Experiment I B Observation Sessions Mean Difference Proportion t 1 and 2 0.095 1.12 2 and 3 0.122 1.43 1 and 3 0.217 2.55* *p < 0.05 20 Amount of Perceptual Learning: C. Number and Duration of Exposures to Training S t i m u l i Experiment I A demonstrated that increasing the f r e -quency of presentation of the learning stimulus-pair during the t r a i n i n g period increases the proportion of i t s subsequent disappearances. Experiment I C was performed to see whether increasing the duration of each presentation would have the same e f f e c t . Since Experiments I A and I B indicated that ex-posure to a luminous target during the te s t period a f f e c t s l a t e r disappearances of t h i s target, two comparable targets, with and without t r a i n i n g , were used for the comparison, rather than the same target before and a f t e r t r a i n i n g . Method Subjects The Ss were 52 college student volunteers. Twelve Ss served i n a preliminary t e s t to determine the targets which would be used i n the post-learning te s t ; of the 40 other sub-j e c t s , ten were randomly assigned to each of four perceptual learning conditions. 21 Preliminary Test The s t i m u l i were three luminous t h r e e - l e t t e r targets (GGR, PPL and RRS). These p a r t i c u l a r l e t t e r s were chosen be-cause they included both s t r a i g h t l i n e s and curved l i n e s and because of the s i m i l a r frequencies of occurrence of the pai r s GR (490), PL (498), and RS (470) as reported i n the table of bigram frequencies by Underwood (1960). The l e t t e r s were of the same dimensions and viewed at the same distance as the d i g i t - t a r g e t s described previously. Each S_ viewed each of the targets for 5 min. Two Ss were assigned at random to each of the six possible orders of the three targets. Perceptual Learning Experience Display materials consisted of 2 x 2 i n . s l i d e s pro-jected on a ground glass screen, the s t i m u l i (letters) each subtended a v i s u a l angle of 2.8 degrees. Each s l i d e contained one word. S i x t y words had been prepared, each consisting of 4 to 13 l e t t e r s and containing the l e t t e r sequence GR. Forty control words were selected which did not contain the l e t t e r s G and R. None of the words contained the sequence PL. Within both l i s t s were several deliberate s p e l l i n g e r r o r s . 22 There were four d i f f e r e n t exposure conditions: (a) 20 GR words and 80 control words, randomly ordered, each shown for 5 sec. (b) 20 GR words and 40 control words, randomly ordered, each shown for 15 sec. (c) 60 GR words and 40 control words, randomly ordered, each shown for 5 sec. (d) 60 GR words, randomly ordered, each shown fo r 15 sec. The Ss were instructed to look for and report s p e l l i n g errors i n each word. Post-Learning Test The 40 Ss who had been given the perceptual learning experience were then given a t e s t under reduced stimulation conditions with targets PPL and GGR. Results The r e s u l t s concerning disappearances i n the pre-liminary t e s t are presented i n Table XVIII i n the appendix. The purpose of t h i s preliminary t e s t was to f i n d two 23 targets which were very s i m i l a r i n the proportions of i d e n t i c a l -and d i f f e r e n t - p a i r disappearances. A t e s t of significance of the mean difference between targets PPl and GGR was performed, and the t value obtained (t=0.054) was f a r from s i g n i f i c a n t . These targets were therefore chosen for the perceptual learning t e s t . Table XiX displays the r e s u l t s concerning disappearances for the targets PPL and GGR following the perceptual learning experience. To show that the proportions of i d e n t i c a l - p a i r disap-pearances without perceptual learning was s i g n i f i c a n t l y d i f -ferent from chance, binomial tests were performed for target PPL. I d e n t i c a l p a i r s d i d disappear and appear together s i g -n i f i c a n t l y more than other p a i r s (see Table XVI i n the appendix). In order to determine whether or not any s i g n i f i c a n t differences existed i n PL paired disappearances for the four learning conditions, an F r a t i o was obtained which did not lead to r e j e c t i o n of the n u l l hypothesis (F=2.1, df=3,36). An Analysis of Variance for proportions of t r a i n i n g - p a i r disappearances was performed and i s summarized i n Table VII. S i g n i f i c a n t F r a t i o s were found. 24 Table VII. Analysis of Variance f o r Proportions of Training-Pair Disappearances i n Experiment I C Source of V a r i a t i o n Sum of Squares df Mean Square F Between Subjects 2.52 39 A (Learning Condition) 1.04 3 0.347 8.46* Subjects within groups 1.48 36 0.041 Within Subjects 8.70 40 B (With/Without Training) 6.36 1 6.36 302.8 * AB Interaction 1.57 3 0.523 24.9 * B X Subjects within groups 0.77 36 0.021 * p <- 0.01 The hypothesis was tested that the differences i n proportions between paired disappearances with and without t r a i n i n g were due to chance, for each presentation condition. The r e s u l t s of the t tests are given i n Table VIII and support the perceptual learning hypothesis. In comparison to PL disappearances, a s i g n i f i c a n t proportion of disappearances did occur for the t r a i n i n g p a i r (GR) i n those three t r a i n i n g conditions with 20 exposures for 15 seconds, 60 for 5 seconds and 60 f o r 15. 25 I t appears t h a t 20 e x p o s u r e s f o r 5 seconds were n o t s u f f i c i e n t t o produce e v i d e n c e o f p e r c e p t u a l l e a r n i n g i n t h i s s i t u a t i o n . T a b l e V I I I . T e s t s f o r S i g n i f i c a n c e of Mean D i f f e r e n c e i n P r o p o r t i o n s o f P a i r e d D i s a p p e a r a n c e s W i t h and W i t h o u t T r a i n i n g i n E x p e r i m e n t IC T r a i n i n g C o n d i t i o n Mean D i f f e r e n c e t. 20-5 0.101 1.55 20-15 0.586 9.02* 60-5 0.739 11.37* 60-15 , 0.828 12.74* * p < 0.01 The d a t a i n T a b l e V I I I show t h a t the mean d i f f e r e n c e p r o p o r t i o n s o f t r a i n i n g - p a i r d i s a p p e a r a n c e s i n c r e a s e s as the number o f e x p o s u r e s and exposure time i s i n c r e a s e d . T e s t s o f s i g n i f i c a n c e o f the d i f f e r e n c e s between c o n d i t i o n s were p e r -formed and are p r e s e n t e d i n T a b l e I X . 26 Table IX. Tests f o r Significance of Differences i n Mean Difference Proportions of Training-Pair Disap-pearances Between Training-Condition Groups i n Experiment I C Conditions Compared M, -Md 2 1 20-5 vs 20-15 0.485 5.39** 20-5 vs 60-5 0.698 7.76** 20-5 vs 60-15 0.727 8.08** 20-15 vs 60-5 0.153 1.70 20-15 vs 60-15 0.242 2.69* 60-5 vs 60-15 0.089 0.99 * p <0.05 ** p<0.01 EXPERIMENT II Temporal and S p a t i a l Relations Experiment II was performed to investigate the d i f -ference between sequential and simultaneous presentation con-d i t i o n s i n producing perceptual learning. I t was hypothesized that i f such learning occurred s o l e l y through S-S associations, 27 simultaneous presentation would be more e f f e c t i v e than sequential. S t i m u l i presented simultaneously were ei t h e r single spaced or double spaced; the sequential presentation occurred at rates of one stimulus per second, or one every three seconds. These conditions were designed to investigate whether such differences i n temporal and s p a t i a l r e l a t i o n s would s i g n i f i c a n t l y a f f e c t the amount of perceptual learning produced. No s p e c i f i c hypotheses concerning t h e i r r e l a t i v e effectiveness were made. Method Subjects The Ss were 30 college student volunteers. Ten Ss were randomly assigned to each of three perceptual learning s i t u a -t i o n s . Perceptual Learning Experience The display materials again were 2 x 2 i n . s l i d e s pre-pared from l i s t s of words containing GR and containing no G's or R*s. Some of the words were d e l i b e r a t e l y misspelled. The s l i d e s were made up to present the l e t t e r s forming these words e i t h e r sequentially or simultaneously. Four presentation 28 conditions were established. S l i d e s were prepared so that the l e t t e r s of each of the 60 GR words could be presented simul-taneously (on one slide) e i t h e r single or double spaced. In these two conditions the 60 s l i d e s were randomly arranged with the 40 word s l i d e s containing no G's or R's. Data f o r the single-spaced condition were taken from Experiment I C. In the sequential conditions the l e t t e r s forming the 60 GR words were presented with an i n t e r - l e t t e r i n t e r v a l of ei t h e r one or three seconds. The S_ f i x a t e d on the screen monocularly with the r i g h t eye as usual. Each l e t t e r or space subtended a v i s u a l angle of 2.8 degrees. In the simultaneous presentation condition the Ss were asked to look for and report s p e l l i n g errors; i n the sequential conditions h a l f the Ss d i d t h i s and h a l f were asked to count the number of l e t t e r s i n each word. Post-Learning Test The luminous targets GGR and PPL were used f o r a l l Ss. One h a l f the Ss viewed PPL f i r s t , while the remaining Ss were f i r s t exposed to GGR. Each target was viewed for 5 min. 29 Results The r e s u l t s concerning disappearances for the two targets, PPL and GGR, are presented i n Table XX i n the appendix. As i n the previous experiments i t was shown that without perceptual learning experience the proportions of i d e n t i c a l -p a i r disappearances were s i g n i f i c a n t l y greater than proportions of other p a i r s (Table XVI), and that there were no s i g n i f i c a n t differences i n PL paired disappearances for the four presenta-t i o n conditions (F=0.93; df 3,36). An Analysis of Variance was performed on proportions of t r a i n i n g - p a i r disappearances, Table X. Table X. Analysis of Variance for Proportions of Training-p a i r Disappearances i n Experiment,II Source of V a r i a t i o n Between Subjects A (Learning Condition) Subjects within groups Within Subjects B (With/Without Training) AB Interaction B X Subjects within groups * p < 0.01 Sum of Mean Squares df Square F 0.86 39 0.36 3 0.120 8.57* 0.50 36 0.014 9.94 40 9.07 1 9.07 453.5 * 0.15 3 0.050 2.5 0.72 36 0.020 30 For each presentation condition, the hypothesis was tested that the differences i n proportions between paired disappear-ances with and without t r a i n i n g were due to chance. In compari-son to PL disappearances a s i g n i f i c a n t increase i n the propor-tions of disappearances d i d occur for the tra i n i n g p a i r (GR) under a l l t r a i n i n g conditions. The r e s u l t s of these t tests are displayed i n Table XI and support the perceptual learning hypothesis. Table XI. Tests of Significance of Differences i n Mean Proportions of Paired Disappearances With and Without Training Training Condition Single-space-simultaneous Double-space-simultaneous One-second-sequential Three-secnnds-seque n t i a l Mean Difference 0.739 0.720 0.478 0.707 11.73* 11.43* 7.59* 11.22* * p < 0.01 A s t a t i s t i c a l comparison of the disappearance propor-tions for the two sequential and the two simultaneous presenta-t i o n conditions revealed a s i g n i f i c a n t r e s u l t (t=2.60, p ~^ 0.05). 31 A comparison of the double-spaced simultaneous and the one-second sequential presentation conditions was also made (t=4.57, p<0.01). The j u s t i f i c a t i o n for s e l e c t i n g these two conditions f o r comparison i s that double spacing resulted i n a mean number of 5.6 l e t t e r s per s l i d e for the 5 sec. presenta-t i o n period; the average time per l e t t e r , therefore, was 0.9 s e c , which i s almost equivalent to the one-second viewing time i n the sequential presentation. In order to determine whether differences i n the s p a t i a l separation between the c r u c i a l stimulus p a i r (GR) resulted i n a s i g n i f i c a n t difference i n the effectiveness of the perceptual learning, a t t e s t was performed. No s i g n i f i c a n t difference (t=0.36) was found between disappearances observed f o r the t r a i n i n g p a i r (GR) under single-spaced and double-spaced simul-taneous presentation conditions. S i m i l a r l y , the hypothesis was tested that the temporal separation between the s t i m u l i would r e s u l t i n s i g n i f i c a n t differences between the propor-tions of disappearances recorded with one-second and three-second sequential presentation; a s i g n i f i c a n t t was obtained (t-4.32, p<0.01). F i n a l l y , no s i g n i f i c a n t differences were obtained when the tasks ( s p e l l i n g , counting) were compared. 32 EXPERIMENT I I I Auditory Perceptual Learning Experiments I and II demonstrated that v i s u a l experience with a stimulus a f f e c t s l a t e r v i s u a l disappearances of t h i s stimulus under reduced stimulation conditions. An inter-modal hypothesis p r e d i c t s that i f perceptual learning has occurred, comparable auditory t r a i n i n g should have the same e f f e c t . Ex-periment I I I was designed to t e s t such a hypothesis. A further refinement was made to get more evidence on temporal r e l a t i o n s between s t i m u l i , by presenting the auditory s t i m u l i at d i f -ferent rates. The same r e l a t i o n s as were found i n Experiment II were expected. Method Subjects The Ss were 30 college student volunteers. Five sub-j e c t s were randomly assigned to each of s i x perceptual learning situations., Auditory Perceptual Learning Experience The same l i s t of 60 words containing GR as i n Experiment 33 II was used. The words were randomly ordered and recorded on four tapes (Uher 4000 Report S tape recorder) with a 4 sec. inter-word i n t e r v a l . Each of the tapes gave a d i f f e r e n t presentation rate. The l e t t e r s were presented 1 , 1, 2 or 3 sec. apart. Several deliberate s p e l l i n g mistakes occurred on each tape. The Ss were directed to l i s t e n to the recorded messages. For each presentation rate, 5 randomly assigned Ss were asked to l i s t e n f or and report s p e l l i n g e r r o r s . The remaining 10 Ss were asked to count the number of l e t t e r s i n each message. Of these 10 Ss, f i v e were assigned to the ^ sec. presentation rate and f i v e to the 3 sec. rate. V i s u a l Post-Learning Test The luminous s t i m u l i GGR and PPL were each viewed for 5 min. by a l l Ss. One h a l f the Ss viewed PPL f i r s t , one hal f , GGR. Results The r e s u l t s concerning disappearances for the two targets are presented i n Table XXI i n the appendix. 34 As i n previous experiments i t was found that without t r a i n i n g i d e n t i c a l l e t t e r s (PP) did disappear and appear to-gether s i g n i f i c a n t l y more often than other p a i r s (Table XVI). No s i g n i f i c a n t differences were found i n PL paired disap-pearances for the s i x presentation conditions (F=1.12# df=5,24). Differences i n proportions between paired disappearances with and without t r a i n i n g were found to be s i g n i f i c a n t under a l l t r a i n i n g conditions, supporting the perceptual learning hypothesis (see Tables XII and X I I I ) . Table XII. Analysis of Variance for Proportions of Training-Pair Disappearances i n Experiment I I I Source of V a r i a t i o n Sum of Squares df Mean Square F Between Subjects 0.75 29 A (Learning Condition) 0.15 5 0.030 1.20 Subjects within Groups 0.60 24 0.025 Within Subjects 6.46 30 B (With/Without Training) 5.16 1 5.16 147.43* AB Interaction 0.45 5 0.090 2.57 B X Subjects within groups 0.85 24 0.035 * p<0.0l 35 Table XIII. Tests for Significance of Mean Difference i n Proportion of Disappearances with and Without Training Training Conditions (in seconds) k + 2 * 3 * i * 3 * Mean Difference t (Proportion GR-PL) 0.654 5.45* 0.715 5.95* 0.605 5.04* 0.796 6.63* 0.258 2.15* 0.514 4.28* / Task was looking for s p e l l i n g e r r o r s . f Task was counting l e t t e r s . * p < 0.05 ** p < 0.01 Inspection of the data with regard to differences i n the effectiveness of the d i f f e r e n t presentation rates and conditions suggests increasing the i n t e r - l e t t e r i n t e r v a l r e s u l t s i n increasingly e f f i c i e n t perceptual learning. The inspection also suggests that looking for s p e l l i n g errors 36 produces a greater strengthening of perceptual associations than the counting l e t t e r s task. However a s t a t i s t i c a l com-parison of a l l conditions reveals no s i g n i f i c a n t differences (F=1.20). Summary of Results Disappearances were divided into those r e l a t e d to " i d e n t i c a l " (e.g. -55 and 8—) and "training" (e.g. 85- and — 5 ) stimulus-pairs. Disappearance of a l l d i g i t s simultaneously, or center d i g i t s alone, or both outside d i g i t s were not i n -cluded i n the s t a t i s t i c a l analysis. I t was shown that i d e n t i c a l stimulus-pairs disappear together more frequently than any other p a i r s i n targets which have not been used f o r perceptual t r a i n i n g . Individual binomial t e s t r e s u l t s are given i n Table XVI. Table XIV shows the binomial tests performed for grouped subjects i n a l l ex-periments. In each experiment i t was shown that no s i g n i f i c a n t d i f -ferences i n pre-learning t r a i n i n g - p a i r disappearances existed between d i f f e r e n t condition groups. 37 Table XIV. Binomial Tests for Tot a l Proportions of I d e n t i c a l -P a i r Disappearances i n Targets Without Training f o r A l l Experiments Experiment N Number of Subjects Number of Subjects p* With > .500 With 4 .500 Iden t i c a l - P a i r I d e n t i c a l - P a i r Disappearances Disappearances I. A I C II I I I 50 40 40 30 48 38 39 29 2 2 1 1 0.000 0.000 0.000 0.000 * p=probability of t h i s proportion or greater occurring by chance The proportions of t r a i n i n g - p a i r disappearances before and a f t e r or with and without t r a i n i n g were compared for a l l conditions i n each experiment. S i g n i f i c a n t differences were found for conditions 45, 60 and 75 i n Experiment I A; 20-15, 60-5, and 60-15 i n Experiment I C; and f o r a l l conditions i n Experiments II and I I I . Tests of sign i f i c a n c e were also performed on the d i f -ferences between conditions i n some experiments. In Experiment I A condition 0 was found to be s i g n i f i c a n t l y d i f f e r e n t from 38 a l l o t h e r c o n d i t i o n s e x c e p t 30. I n E x p e r i m e n t I B t h e r e was a s i g n i f i c a n t d i f f e r e n c e between o b s e r v a t i o n s e s s i o n s 1 and 3. I n E x p e r i m e n t I C c o n d i t i o n 20-5 was s i g n i f i c a n t l y d i f f e r e n t from a l l o t h e r c o n d i t i o n s , and 20-15 from 60-15. I n E x p e r i -ment I I a c o m p a r i s o n o f s e q u e n t i a l and s i m u l t a n e o u s p r e s e n t a -t i o n c o n d i t i o n s showed s i m u l t a n e o u s t o be more e f f e c t i v e t h a n s e q u e n t i a l i n p r o d u c i n g p e r c e p t u a l l e a r n i n g . I n t h i s e x p e r i -ment t o o , t h r e e - s e c o n d was found t o be s u p e r i o r t o one-second p r e s e n t a t i o n r a t e . No s i g n i f i c a n t d i f f e r e n c e s were found when t a s k s , t e m p o r a l s e p a r a t i o n i n E x p e r i m e n t I I I , o r s p a t i a l s e p a r a t i o n were compared. A t r e n d a n a l y s i s o f mean d i f f e r e n c e s i n p r o p o r t i o n s o f t r a i n i n g - p a i r d i s a p p e a r a n c e s b e f o r e and a f t e r p e r c e p t u a l l e a r n i n g as a f u n c t i o n o f the number o f exposure p a i r i n g s was c a r r i e d o u t f o r d a t a o f E x p e r i m e n t I A. A s i g n i f i c a n t l i n e a r t r e n d was de m o n s t r a t e d . 39 Discussion In t h i s series of experiments the perceptual ex-perience of a subject was manipulated i n order to assess the e f f e c t of sensory-sensory associations on luminous figure disappearances observed under reduced stimulation condi-tio n s . I t was found that s t i m u l i which were paired i n the perceptual experience disappeared or appeared together i n the post-learning t e s t s i g n i f i c a n t l y more often than without such t r a i n i n g . This occurred despite the fa c t that the perceptual learning had to work against an association between i d e n t i c a l s t i m u l i , an association which had been demonstrated i n both t h i s and previous research. Concurrent disappearances of p a r a l l e l l i n e s and i d e n t i c a l forms under conditions s i m i l a r to t h i s experiment have been reported by Replogle (1962), Tees (1961) and McKinney (1963). More-over, using forms scaled for s i m i l a r i t y , Donderi (1966) found the duration of simultaneous disappearance of two forms increased with increase i n t h e i r form-pair s i m i l a r i t y . In t h i s experiment, with a l l the targets used, the i d e n t i c a l d i g i t s or l e t t e r s disappeared together s i g n i f i c a n t l y more frequently than the discriminably d i f f e r e n t stimulus pa i r s i f no perceptual t r a i n i n g had been given. 40 The f o l l o w i n g e x p l a n a t i o n f o r the l i n k between i d e n t i c a l forms i s o f f e r e d . H u b e l and W e i s e l ' s (1965) r e s e a r c h c o n c e r n i n g the n e u r a l m e d i a t i o n o f form d i s c r i m i n a -t i o n i m p l i e s t h a t w i t h r e l a t i v e l y complex forms such as d i g i t s o r l e t t e r s , s i m i l a r d e s i g n s would e x c i t e a g r e a t number o f c e l l s i n common. I f d i s a p p e a r a n c e s under s i m p l i -f i e d s t i m u l u s c o n d i t i o n s a re a consequence o f c e n t r a l p r o c e s s i n h i b i t i o n r e s u l t i n g from r e d u c e d s t i m u l u s i n p u t (Hebb, 1963) t h e n a h i g h degree o f n e u r a l o v e r l a p s h o u l d r e s u l t i n a h i g h p r o p o r t i o n o f j o i n t d i s a p p e a r a n c e s and appearances f o r i d e n t i c a l s t i m u l u s p a i r s . F a t i g u e f o r the n e u r a l r e p r e s e n t a t i v e s o f one o f the p a i r would mean f a t i g u e f o r the c e l l s o f the o t h e r . T h i s l i n k between i d e n t i c a l s t i m u l i makes i t a l l the more r e m a r k a b l e , t h e r e f o r e , t h a t d i s c r i m i n a b l y d i f f e r e n t s t i m u l i came t o d i s a p p e a r t o g e t h e r a f t e r m e r e l y a number o f p a i r i n g s i n the p e r c e p t u a l e x p e r i e n c e . The r e s u l t s o f t h e s e e x p e r i m e n t s seem t o c o n c u r w i t h Hebb's (1949) o r i g i n a l h y p o t h e s i s t h a t c e l l a s s e m b l i e s and phase sequences d e v e l o p s o l e l y as a r e s u l t o f c o n t i g u i t y . As a consequence o f t h e i r p r e v i o u s c l o s e t e m p o r a l and s p a t i a l c o n c u r r e n c e the n e u r a l r e p r e s e n t a t i v e s o f the t r a i n i n g s t i m u l i i n h i b i t and 41 f a c i l i t a t e e a c h o t h e r ' s f i r i n g a n d t h i s i s e v i d e n c e d b y j o i n t d i s a p p e a r a n c e s i n t h e p o s t - l e a r n i n g t e s t . A n i m p o r t a n t p a r t o f t h i s e x p e r i m e n t was t h e p e r -c e p t u a l l e a r n i n g e x e r c i s e e m p l o y e d . The e x e r c i s e e v o l v e d f r o m r e s e a r c h c i t e d e a r l i e r , d e a l i n g w i t h t h e n a t u r e o f i m -m e d i a t e m e m o r y . I n t h e p r e v i o u s e x p e r i m e n t s , t h e s u b j e c t l i s t e n e d t o n i n e - d i g i t s e r i e s a n d r e p e a t e d e a c h s e r i e s f o l -l o w i n g i t s p r e s e n t a t i o n . One c r i t i c a l s e r i e s r e c u r r e d e v e r y t h i r d t r i a l . R e g a r d l e s s o f t h e p r a c t i c e e f f e c t n o t e d t h r o u g h t h e 24 t r i a l s , c u m u l a t i v e l e a r n i n g o f t h e c r u c i a l s e r i e s d i d t a k e p l a c e a n d r e i n f o r c e m e n t f r o m b e i n g t o l d o f m i s t a k e s a n d c o r r e c t s e r i e s d i d n o t a f f e c t t h e r a t e o f t h i s l e a r n i n g ( T e e s , 1960). I n t h e p r e s e n t e x p e r i m e n t i f t h e s u b j e c t s * r e s p o n s e h a d a l s o b e e n t o r e p e a t t h e d i g i t s o b s e r v e d i n t h e v i s u a l d i s p l a y , s e v e r a l c o n f o u n d i n g v a r i a b l e s w o u l d h a v e b e e n i n t r o -d u c e d . I n t h a t p r o c e d u r e , r e i n f o r c e m e n t may s t i l l h a v e b e e n i n v o l v e d . T h o u g h t h e s u b j e c t s w e r e p r e s u m a b l y n o t m o t i v a t e d t o r e m e m b e r t h e c r u c i a l s e r i e s o f d i g i t s a f t e r t h e n e x t h a d b e g u n , t h e y w e r e c e r t a i n l y m o t i v a t e d t o r e m e m b e r a n d r e p e a t t h e i n d i v i d u a l s e t s o f d i g i t s . I n r e p e a t i n g t h e s e r i e s , t h e s u b j e c t s a l s o d e r i v e d a n i n f o r m a t i o n a l o r f e e d b a c k 42 source o f r e i n f o r c e m e n t . I n the p r e s e n t e x p e r i m e n t s , s i n c e t h e s u b j e c t s were a s k e d t o r e p o r t the t o t a l number o f d i g i t s o r l e t t e r s i n e a c h v i s u a l d i s p l a y o r t o l o o k f o r s p e l l i n g m i s t a k e s , t h e y were assumably m o t i v a t e d t o c a r r y out a t a s k i r r e l e v a n t t o t h e c r u c i a l p e r c e p t u a l l e a r n i n g e x p e r i e n c e . What the t a s k c o m p r i s e s does n o t appear t o be v e r y i m p o r t a n t t o the amount o f p e r c e p t u a l l e a r n i n g p r o d u c e d s i n c e t h e t a s k c o m p a r i s o n a n a l y s i s r e v e a l e d no s i g n i f i c a n t d i f f e r e n c e be-tween t a s k s . S i n c e the s u b j e c t s were engaged i n an i r -r e l e v a n t a c t i v i t y , i t i s l e s s l i k e l y t h a t t h e i r a t t e n t i o n w o u l d be c a l l e d t o f r e q u e n t c o n c u r r e n c e o f the t r a i n i n g p a i r s i n t h e v i s u a l d i s p l a y s , o r t h a t m o t i v a t i o n a l v a r i a b l e s would a f f e c t t h e i r r e p o r t s . When q u e s t i o n e d c a s u a l l y a f t e r the e x p e r i m e n t , most s u b j e c t s d i d r e v e a l t h a t t h e y had n o t been aware o f t h e f r e q u e n t c o n c u r r e n c e o f the l e t t e r o r d i g i t p a i r s . The most i m p o r t a n t c o n s i d e r a t i o n r e g a r d i n g t h e p r o b l e m o f v e r b a l r e p o r t s , however, has t o do w i t h the p o s -s i b l e i n t r o d u c t i o n o f r e s p o n s e t r a i n i n g and/or b i a s , w h i c h a c c o r d i n g t o some i n v e s t i g a t o r s (Schuck and Leahy, 1966) i s r e s p o n s i b l e f o r the preponderance o f m e a n i n g f u l fragments 4 3 w h i c h r e p o r t e d l y d i s a p p e a r i n such s i t u a t i o n s . I f the sub-j e c t s i m p l y r e p e a t e d th e s t i m u l i i n e a c h v i s u a l d i s p l a y , n o t o n l y w o u l d the v i s u a l s t i m u l i be a p p e a r i n g i n c l o s e t e m p o r a l and s p a t i a l c o n n e c t i o n , b u t a l s o t h e s e v e r b a l r e p o r t s would be c o n c u r r i n g w i t h e q u a l f r e q u e n c y . By h a v i n g the s u b j e c t r e p o r t t h e t o t a l number o f s t i m u l i o r s p e l l i n g m i s t a k e s , the p e r c e p t u a l l e a r n i n g e x p e r i e n c e i s r e s t r i c t e d t o S-S a s s o c i a t i o n s r a t h e r t h a n R-R o r S-R-R-S a s s o c i a t i o n s . I t w i l l be r e c a l l e d t h a t i n E x p e r i m e n t I A a second t a r g e t was v i e w e d s o l e l y i n the p o s t - l e a r n i n g s i t u a t i o n . T h i s was t o check whether e x p e r i e n c e i n t h e p r e - l e a r n i n g t e s t w i t h d i g i t t r i p l e t s d i d i t s e l f i n f l u e n c e l a t e r d i s a p p e a r a n c e s i n the p o s t - t e s t . I f the p r o p o r t i o n o f t r a i n i n g p a i r d i s a p -p e a r a n c e s w i t h the t a r g e t seen s o l e l y i n the p o s t - t e s t had been s i g n i f i c a n t l y l o w e r t h a n t h o s e o b t a i n e d w i t h t h e t r a i n i n g p a i r seen i n b o t h p r e - and p o s t - l e a r n i n g t e s t s , d a t a i n t e r -p r e t a t i o n i n v o l v i n g a t t e n t i o n a l v a r i a b l e s m i g h t be s u g g e s t e d . T h i s d i d n o t o c c u r . I n f a c t , e v i d e n c e o f p e r c e p t u a l l e a r n i n g w i t h t h i s t a r g e t was e ven g r e a t e r f o r each exposure f r e -quency. T h i s s u g g e s t e d t h a t d i f f e r e n c e s i n t a r g e t f a m i l i a r i t y 44 a f f e c t d i s a p p e a r a n c e s . E x p e r i m e n t I B was p e r f o r m e d t o i n -v e s t i g a t e t h i s p o s s i b i l i t y . I t was f o u n d t h a t , l i k e the d i s -a ppearances o f groups o f c u r l i c u e s i n P r i t c h a r d ' s (1961) r e p o r t , the p r o p o r t i o n s o f i d e n t i c a l - p a i r d i s a p p e a r a n c e s i n c r e a s e d w i t h i n c r e a s e d time s p e n t o b s e r v i n g t h e t a r g e t . Thus, t o p r e v e n t p e r c e p t u a l l e a r n i n g from o c c u r r i n g d u r i n g the t e s t i t s e l f and a l s o t o a v o i d i n v o l v i n g a t t e n t i o n as much as p o s s i b l e , i n subsequent e x p e r i m e n t s comparable t a r g e t s w i t h and w i t h o u t t r a i n i n g were used t o g e t a measure o f p e r c e p t u a l l e a r n i n g , r a t h e r t h a n the same t a r g e t b e f o r e and a f t e r t r a i n i n g . I n E x p e r i m e n t s I A and I C i t was shown t h a t i n -c r e a s i n g the number of e x p o s u r e s d u r i n g the t r a i n i n g i n -c r e a s e d th e e f f e c t i v e n e s s o f the p e r c e p t u a l l e a r n i n g . I n -s p e c t i o n o f F i g u r e 1 and t h e t r e n d a n a l y s i s s u g g e s t t h a t the e f f e c t o f i n c r e a s i n g t h e number o f l e a r n i n g e x p e r i e n c e s on i n t e g r a t i o n o f n e u r a l r e p r e s e n t a t i v e s o f t r a i n i n g p a i r s i s g r a d u a l and l i n e a r . That 45 p a i r e d e x p o s u r e s were r e q u i r e d ( I A) t o produce s i g n i f i c a n t e v i d e n c e o f p e r c e p t u a l l e a r n i n g i s n o t s u r p r i s i n g . The n a t u r e o f t h e t a s k ( c o u n t i n g d i g i t s , w h i c h were o f t e n misshapen) r e s u l t s i n l a c k o f a t t e n t i o n t o the c r u c i a l p a i r , d i g i t s p e r s e , and perhaps t h e e n t i r e 45 task i t s e l f . For the subjects, the task might e a s i l y have become one of counting shapeless forms i n each display. The assymptotic function observed with greater than 45 pairings i n the experiment may be the r e s u l t of subjects" reporting the t o t a l number^ of disappearance-appearance changes rather than t o t a l time involved i n each p a i r p o s s i -b i l i t y . Consequently the c o l l e c t i o n of duration information may provide an even better measuring device. Another pos-s i b l y f i n e r measurement might be obtained by giving post-tests at various i n t e r v a l s a f t e r the perceptual experience to see how long the perceptual association p e r s i s t s . One would expect that with a greater number of p r i o r S-S pairings the association e f f e c t would be demonstrable longer. Increasing the duration of each i n d i v i d u a l exposure w i l l also increase the strength of association. This i s shown i n Experiment I C i n which 20 exposures for 15 seconds each was s u f f i c i e n t to produce evidence of perceptual learning, whereas 45 exposures at 5 seconds each were neces-sary i n Experiment I A. Exposure condition 60-5 apparently produced even stronger perceptual association than 20-15. Although exposure to t r a i n i n g s t i m u l i i n both these condi-tions were t h e o r e t i c a l l y the same, i n practice t h i s was probably not so. The subject was instructed to look at 46 the whole word and probably spent most of h i s time looking at and for s p e l l i n g errors not at the l e t t e r s GR. Thus the more frequently the l e t t e r p a i r was presented, the more l i k e l y i t i s that the subject observed i t . The difference between these two exposure conditions was 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 ; i f the time spent by the subject looking at the t r a i n i n g s t i m u l i could be controlled, i t might be possible to demonstrate that the perceptual learning produced i n both conditions i s i d e n t i c a l . With 60 exposures for 15 seconds each the perceptual learning was even more evident. This i s i n agreement with the l i n e a r trend observed i n Experiment I A. An experiment was performed to investigate the d i f -ferences between sequential and simultaneous presentation conditions i n producing perceptual learning. S t a t i s t i c a l t r i a l comparison of the two sequential and two simultaneous conditions, and comparison of the one-second sequential and double-spaced simultaneous conditions revealed s i g n i f i c a n t differences i n the disappearance phenomena. Simultaneous presentation was found to be superior. Decreasing the presentation rate may also improve the strength of perceptual associations formed as a r e s u l t of 47 c o n t r o l l e d learning. A s i g n i f i c a n t r e s u l t was obtained i n Experiment I I i n regard to the mean proportions difference between t r a i n i n g and non-training p a i r s for the two sequential presentation conditions. S i m i l a r l y i n Experiment I I I (auditory presentation) greater perceptual learning was e v i -denced when the presentation rate was decreased ( 2 second: 0.699; 1 second: 0.715; 2 second: 0.733; 3 second: 0.870), although these differences 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 . The s p a t i a l separation of the t r a i n i n g s t i m u l i i n the Experiment II simultaneous presentation conditions was apparently not s u f f i c i e n t to cause a difference i n the amounts of perceptual learning produced since the mean pro-portions difference was n e g l i g i b l e . I f further subjects and presentation conditions had been used, i t i s possible the differences i n these experiments would have reached s i g n i f i c a n c e . These ideas concerning presentation rate, exposure duration, sequential versus simultaneous presentation and learning f i n d support i n other investigations (reviewed by Posner, 1963). Mackworthfl962, 1965) found more d i g i t s could be r e c a l l e d when d i g i t series were shown simul-taneously than when each d i g i t appeared alone, that more 48 d i g i t s were also r e c a l l e d when the display presentation was longer, and that increasing the speed of presentation reduced the amount which could be r e c a l l e d . Crowder (1966) also demonstrated that r e c a l l of sequential series was i n -versely related to presentation speed, and thai- second for second, simultaneous presentation was more e f f i c i e n t . As well as giving information on presentation rate. Experiment I I I gives evidence for an intermodal perceptual learning hypothesis. Auditory perceptual associations were demonstrated i n a v i s u a l post-learning t e s t . In conclusion, perceptual disappearances under re-duced stimulation conditions seem to provide a remarkably sensitive index of the strength of perceptual associations. They are useful i n demonstrating the existence of perceptual learning, and p a r t i c u l a r l y i n supporting Hebb's enrichment theory of perceptual association. A s p e c i f i c i t y theory (Gibson and Gibson, 1955), which maintains that perceptual learning i s l i m i t e d to changes which can be explained on the basis of improvement i n discrimination of variables present i n the stimulus, i s inadequate to explain the data from these experiments. 49 References Clarke, F.J.J, and Belcher, S.J. On the l o c a l i z a t i o n of Troxler's e f f e c t i n the v i s u a l pathway. V i s i o n Res.. 1962, 2, 53-68. Clarke, F.J.J, and Evans, C.R. Luminous design phenomenon. Science. 1964, 144, 1359. Craig, E.A. and Lichtenstein, M. V i s i b i l i t y - i n v i s i b i l i t y cycles as a function of stimulus o r i e n t a t i o n . Amer.  J . Psychol., 1953, 66, 554-563. Deitcher, J . Memory trace i n d i g i t r e p e t i t i o n . 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The e f f e c t of prolonged exposure to v i s u a l patterns on learning to discriminate s i m i l a r and d i f f e r e n t patterns. J . comp. phys i o l . Psychol., 1958, 51, 584-587. 50 Gibson, J . J . and Gibson, E.J. Perceptual learning: d i f f e r e n -t i a t i o n or enrichment? Pls/yschol. Rev., 1955, 62, 32-41. Hart, J.T. Luminous figures: influence of point of f i x a t i o n on t h e i r disappearance. Science, 1964, 143, 1193-1194. Hebb, D.O. The organization of behaviour. New York: Wiley, 1949. Hebb, D.O. D i s t i n c t i v e features of learning i n the higher animal. In J.F. Delafresnaye (ed.), Brain mechanisms  and learning. S p r i n g f i e l d : Thomas, 1961, 37-51. Hebb, D.O. The semi autonomous process: i t s nature and nurture. Aroer. Psychol., 1963, 1, 16-27. Hubel, D.H. and Wiesel, T.N. Receptive f i e l d s and functional architecture i n two nonstriate v i s u a l areas. J . Neuro-phvsiol.. 1965, 28, 229-289. Mackworth, J.F. 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Aroer., 1961, 466, 2-8. Pritchard, R.M., Heron, W., and Hebb, D.O. V i s u a l perception approached by the method of s t a b i l i z e d images. Can.  J . Psychol., 1960, 14, 67-77. Replogle, A. The e f f e c t s of s i m i l a r i t y on the behaviour of perceived fi g u r e s . Paper read at E.P.A., A t l a n t i c C i t y , 1962. Riesen, A.H. Stimulation as a requirement for growth and function i n behavioral development. In Fiske, D.W. and Maddi, S.R. (eds.): Functions of varied experience. Homewood, 111.: The Dorsy Press, 1961, 57-80. Schuck, J.R., Brock, T.C. and Becher, L.A. Luminous figures: factors a f f e c t i n g the reporting of disappearances. Science, 1964, 146, 1598-1599. Schuck, J.R. and Leahy, W.R. A comparison of verbal and non-verbal reports of fragmenting v i s u a l images. Percep.  and Psvchoiahy., 1966, 1, 191-192. Sie g e l , A.I. Deprivation of v i s u a l form d e f i n i t i o n i n the r i n g dove: I Discriminatory learning. J . camp.  Physiol. Psychol., 1953, 46, 115-119. Senden, M. von, Raum-und Gestaltauffasung bie operierten Blindgeborenen vor und nach der Operation. L e i p s i g : Barth, 1932. Tees, R.C. The e f f e c t s of reinforcement on d i g i t r e p e t i -t i o n . Underg. res, p r o j . Psychol., 1960, 2, 64-70 (McGill U n i v e r s i t y ) . Tees, R.C. The role of f i e l d e f f e c t s i n v i s u a l perception. Underg. res, p r o j . Psychol.. 1961, 3., 87-96 (McGill U n i v e r s i t y ) . 52 Underwood, B.J. and Schulz, R.W. Meaningfulness and  verbal learning. Chicago: Lippincott, 1960. Winer, B.J. S t a t i s t i c a l p r i n c i p l e s i n experimental design. New York: McGraw-Hill, 1962. 53 54 Table XV. Numbers and Proportions of Disappearances for the Two Luminous Targets i n Experiment I A on ^Before Perceptual Learning A f t e r Perceptual Learnina Exposure g T a r g e t A* Target A Target B Frequency — Number Number Proportion Number Number Proportion Trojiorti Identical Training Training Identical Train'iAcj Trqi'mnj Training Pairs Pairs Pfliirs Pairs Vaics Ibu'rs Pairs 1 12 9 .429 19 9 .321 .308 2 13 0 .000 22 1 .043 .545 3 15 0 .000 10 0 .000 .000 4 5 0 .000 17 5 .227 .000 0 5 6 2 .250 5 1 .167 .333 6 3 0 .000 3 1 .250 .000 7 11 1 .083 11 3 .214 .143 8 9 7 .438 8 4 .333 .000 9 3 0 .000 1 0 .000 .000 10 8 0 .000 7 1 .125 .200 £85 £19 X.120 <?103 <?25 X.168 X".l53 1 10 6 .375 16 4 .200 .250 2 10 1 .091 9 4 .308 .400 3 5 2 .286 4 9 .692 1.000 4 18 4 .182 21 4 .160 ;321 5 8 4 .333 10 11 .524 .467 6 12 2 .143 9 4 .308 .210 7 4 1 .200 4 2 .333 .455 8 9 1 .100 11 1 .083 .833 9 7 1 .125 8 4 .333 .091 10 2 1 .333 7 4 .364 .222 £ 85 ^23 X.217 iE.99 £47 X.331 X".425 55 T a b l e XV (Continued) 1 8 2 .200 4 3 .429 .267 2 3 1 .250 9 14 .609 ' .800 3 2 2 .500 3 3 .500 1.000 4 5 0 .000 14 2 .125 .733 5 1 0 .000 3 1 .250 .000 6 4 0 .000 6 2 .250 .571 7 5 5 .500 6 13 .684 .000 8 5 0 .000 0 6 1.000 .750 9 6 1 .143 6 3 .333 .571 10 5 1 .167 5 5 .500 1.000 ^ 4 4 £ 1 2 X.176 ^ 56 ^ 5 2 X~.468 X.569 1 9 3 .250 1 3 .750 .800 2 7 0 .000 3 1 .250 1.000 3 8 0 .000 2 2 .500 .444 4 3 0 .000 3 2 .400 1.000 5 9 2 .182 0 5 1.000 .625 6 2 1 .333 4 15 .789 .750 7 1 0 .000 0 1 1.000 1.000 8 14 1 .067 4 4 .500 .600 9 6 1 .143 0 7 1.000 .545 10 4 2 .333 5 8 .615 .533 £63 £10 X.131 £.22 ^ 4 8 X. 680 X~.730 1 2 1 .333 2 4 .667 .778 2 7 5 .417 4 9 .692 .692 3 4 0 .000 0 6 1.000 1.000 4 7 1 .125 1 6 .857 .900 5 2 0 .000 0 8 1.000 1.000 6 2 0 .000 2 4 .667 1.000 7 5 1 .167 0 8 1.000 .429 8 10 0 .000 3 10 .769 .944 9 11 3 .214 9 11 .550 .533 10 4 2 .333 1 5 .833 .800 £ 5 4 £13 >T.159 £ 2 2 £ 7 1 T.804 X.808 * T a r g e t ( e . g . 855) seen i n b o t h p r e - and p o s t - l e a r n i n g t e s t s . ** T a r g e t ( e . g . 332) seen o n l y i n p o s t - t e s t . 56 Table XVI. Binoraial Tests of Disappearances of Iden t i c a l Pairs i n Targets without Training Training Subject Number of Tot a l Number p * Condition I d e n t i c a l Pairs of Disappearances 1 12 21 .332 2 13 13 .000 3 15 15 .000 4 5 5 .031 0 5 6 8 .145 6 3 3 .125 7 11 12 .003 8 9 16 .402 9 3 3 .125 10 8 8 .004 1 10 16 .227 2 10 11 .006 , 3 5 7 .227 ^ 4 18 22 .002 ^ 30 5 8 12 .194 6 12 14 .006 £ 7 4 5 .187 'C . 8 9 10 .011 £- 9 7 8 .035 LL> 10 2 3 .500 1 8 10 .055 2 3 4 .310 3 2 4 .682 4 5 5 .031 45 5 1 1 .500 6 4 4 .063 7 5 10 .638 8 5 5 .031 9 6 7 .062 10 5 6 .109 * p = probability of the given proportion or greater occurring by chance, one t a i l t e s t . 57 Table XVI (Continued) 1 9 12 .073 2 7 7 .008 3 8 8 .004 4 3 3 .125 60 5 9 11 .033 6 2 3 .500 7 1 1 .500 < 8 14 15 .000 M 9 6 7 .062 10 4 6 .343 c v C 1 2 3 .500 Q- 2 7 12 .317 LU 3 4 4 .063 4 7 8 .035 75 5 2 2 .250 6 2 2 .250 7 5 6 .109 8 10 10 .001 9 11 14 .029 10 4 6 .343 1 3 3 .125 2 2 3 .500 o 3 5 5 .031 4 8 9 .020 IF 2 ° - 5 £ 5 1 4 .930 6 4 4 .062 :peri 7 4 4 .062 :peri 8 1 1 .500 X LU 9 3 6 .336 10 3 3 .125 i 58 Table XVI (Continued) 20-15 1 2 3 4 5 6 7 8 9 10 3 2 1 2 3 2 11 7 6 10 3 2 1 2 3 2 11 7 7 11 .125 .125 .500 .250 .125 .250 .000 .008 .062 .006 O ^60-5 lit 1 2 3 4 5 6 7 8 9 10 7 5 12 2 11 6 2 2 6 5 10 5 14 2 14 6 3 2 8 6 .172 .031 .006 .250 .029 .016 .500 .250 .145 .109 60-15 1 2 3 4 5 6 7 8 9 10 4 5 2 5 10 8 3 4 5 4 4 5 2 5 12 8 3 5 5 4 .062 .031 .250 .031 .019 .004 .125 .187 .031 .062 59 T a b l e XVI ( c o n t i n u e d ) 1 7 10 .172 2 5 5 .031 3 12 14 .006 S i m u l t a n e o u s 4 2 2 .250 S i n g l e - S p a c e 5 11 14 .029 6 6 6 .016 7 2 3 .500 8 2 2 .250 9 6 8 .145 10 5 6 .109 1 8 10 .055 2 3 3 .125 \=\ 3 10. 10 .001 S i m u l t a n e o u s 4 7 8 .035 v Double-Space 5 6 7 .062 \ 6 3 4 .312 u 7 3 3 .125 £~ 8 7 8 .035 uJ 9 5 5 .031 10 10 12 .019 1 1 6 1.000 2 2 2 .250 3 6 6 .015 S e q u e n t i a l 4 1 1 .500 One-Second 5 5 5 .031 6 4 4 .062 7 7 7 .008 8 6 7 .062 9 5 5 .031 10 6 9 .254 60 Table XVI (Continued) M .§ Sequential «_Three-Second x al 1 1 2. 7750 2 5 5 .031 3 5 5 .031 4 4 4 .062 5 5 5 .031 6 3 3 .125 7 3 3 .125 8 1 1 .500 9 5 6 .109 10 1 1 .500 1 3 3 .125 2 8 8 .004 3 2 2 .250 4 7 8 .035 second 5 12 15 .018 6 7 11 .281 7 5 9 .512 8 7 7 .008 9 3 3 .125 10 7 8 .035 -£ 1 3 3 .125 E 2 4 4 .062 1 second 3 9 9 .002 4 6 6 .016 5 3 3 .125 1 7 9 .090 2 10 12 .019 second 3 3 4 .310 4 4 4 .062 5 3 3 .125 X 61 Table XVI (Continued) c 3 second £ D Q _ X LU 1 7 8 .035 2 9 10 .011 3 6 6 .016 4 6 7 .062 5 5 5 .031 6 5 5 .031 7 4 4 .062 8 15 17 .001 9 3 6 .336 10 5 6 .109 62 T a b l e X V I I . Changes i n P r o p o r t i o n s o f I d e n t i c a l - P a i r D i s a p p e a r a n c e s Over Time i n E x p e r i m e n t I B S u b j e c t s O b s e r v a t i o n a l S e s s i o n s 2 3 4 5 6 7 8 9 10 Number Number 'Proportion Different Identical Identical Pairs Pairs Pairs 7 9 1 3 5 3 7 2 3 9 5 3 2 18 7 5 8 7 .556 .563 .357 .750 .400 .783 .700 .417 .800 .700 Number Number 'Proportion Different Identical Identical Pairs 1 14 3 8 Pairs 2 18 11 10 4 7 9 18 .250 .857 .733 .800 1.000 .769 .800 .333 .750 .692 Number Number Proportion Different Identical Identical Pair* Pairs Pairs 5 4 .445 3 13 .813 14 .933 .667 1.000 16 1.000 0 10 12 8 20 23 1.000 .780 .714 .852 £.44 £69 *.603 £ 4 3 £85 y.698 £_34 £119 X.820 63 Table XVIII. Frequencies and Proportions of Disappearances i n Three Targets Subject Target GGK Tarqet PPL- Target R R S Number Number Proportion Numtaer Number Proportion Number Number Proportion Identical Different Different Identical Different Different Identical Different Different Pairi Pairs Pair* Pai >5 fcxi'f-S Pours &irs ?aio Pair 1 4 0 .000 2 0 .000 4 3 .428 2 4 2 .333 10 2 .167 4 2 .333 3 2 0 .000 1 0 .000 0 3 1.000 4 2 0 .000 4 0 .000 ; 2 0 .000 5 6 1 .143 7 5 .417 5 5 .500 6 11 3 .214 12 4 .250 7 0 .000 7 2 4 .667 1 1 .500 0 3 1.000 8 8 4 .333 12 3 .200 6 4 .400 9 6 1 .143 7 0 .000 2 1 .333 10' 6 1 .143 3 1 .250 0 4 1.000 11 4 1 .200 0 0 .000 1 0 .000 12 12 2 .143 3 4 .571 7 9 .562 £ 6 7 £ 1 9 ~X .193 ^ 6 2 £ 2 0 *X .196 ^ 3 8 ^34 3T.463 64 Table XIX. Frequencies and Proportions of Paired Disappearances With and Without Training i n Experiment I C Training S_ Target 1 (No training) Target 2 (Training) Condition Number NJumber "Proportion Number Number Proporl Identical Train ing Trainmq Identical Training Trainii "Pairs Pairs •fci'rs 'Pours Pairs Pairs 1 3 0 .000 4 0 .000 2 2 1 .333 2 0 .000 3 5 0 .000 8 1 .111 4 8 1 .111 12 5 .294 5 1 3 .750 1 2 .667 6 4 0 .000 1 1 .500 7 4 0 .000 2 0 .000 8 1 0 .000 1 0 .000 9 3 3 .500 1 3 .750 10 3 • 0 .000 5 3 .375 £3 4 £ 8 X.169 £ 37 £15 X.270 20-15 1 2 3 4 5 6 7 8 9 10 3 2 1 2 3 2 11 7 6 10 0 0 0 0 0 0 0 0 1 1 .000 .000 .000 .000 .000 .000 .000 .000 .143 .091 1 3 1 1 2 1 4 6. 4 5 7 2 4 2 2 1 6 9 6 6 .875 .400 .800 .667 .500 .500 .600 .600 .600 £ 47 £ 2 X.023 £ 2 8 £45 X.609 65 Table XIX (Continued) 1 7 3 .300 1 13 .928 2 5 0 .000 0 5 1.000 3 12 2 .143 9 18 .667 4 2 0 ' .000 0 2 1.000 5 11 3 .214 4 8 .667 6 6 0 .000 0 4 1.000 7 2 1 .333 0 5 1.000 8 2 0 .000 0 1 1.000 9 6 2 .250 1 7 .875 10 5 1 .167 2 4 .667 £ 58 £ 1 2 "X.141 £ 1 7 £ 6 7 ^T.880 1 4 0 .000 0 2 1.000 2 5 0 .000 0 4 1.000 3 2 0 .000 0 2 1.000 4 5 0 .000 0 5 1.000 5 10 2 .167 3 8 .727 6 8 0 .000 2 5 .714 7 3 0 .000 0 6 1.000 8 4 1 .200 2 8 .800 9 5 0 .000 1 2 .667 10 4 0 .000 1 3 .750 ^ 50 £ 3 Xv037 £ 4 5 X~.865 66 Table XX. Numbers and Proportions of Paired Disappearances With and Without Perceptual Experience i n Experiment II Training Condition O^imultaneous S inqle - Spaced Target PPL (No Training) Target GGR (Training) Number Number I d e n t i c a l Di-fTerent Proportion Different Number Identical Number Different Proportion D i f f e r e n t Pairs f&urs fairs fairs Pairs Pcius 1 7 3 .300 1 13 .928 2 5 0 .000 0 5 1.000 3 12 2 .143 9 18 .667 4 2 0 .000 0 2 1.000 5 11 3 .214 4 8 .667 6 6 0 .000 0 4 1.000 7 2 1 .333 0 5 1.000 8 2 0 .000 0 1 1.000 9 6 2 .250 1 7 .875 10 5 1 .167 2 4 .667 £. 58 £12 X.141 £ 1 7 £.67 X.880 Simultaneous Double - Spaced 1 8 2 .200 4 8 .667 2 3 0 .000 l 5 .833 3 10 0 .000 3 7 .700 4 7 1 .125 0 12 1.000 5 6 1 .143 0 2 1.000 6 3 1 .250 1 3 .750 7 3 0 .000 1 2 .667 8 7 1 .125 0 3 1.000 9 5 0 .000 2 5 .714 10 10 2 .167 1 7 .875 £ 6 2 £ J 77ioi £13 £.54 ^.821 67 Table XX (Continued) S e q u e n t i a l One - Second (spell) (count) Sequential TT^rse second (6pell) (count) 1 1 5 .167 6 1 .143 2 2 0 .000 4 4 .500 3 6 0 .000 2 2 .500 4 1 0 .000 1 1 .500 5 5 0 .000 1 1 .500 6 4 0 .000 2 1 .333 7 7 0 .000 3 6 .667 8 6 1 .143 1 4 .800 9 5 0 .000 2 3 .600 10 6 3 .333 1 7 .875 £ 4 3 )C.064 £ 2 3 £ 30 X . 5 9 2 1 1 1 .500 3 4 .571 2 5 0 .000 2 4 .667 3 5 0 .000 1 5 .833 4 4 0 .000 0 5 1.000 5 5 0 .000 0 6 1.000 6 3 0 .000 1 1 .500 7 3 0 .000 2 3 .600 8 1 0 .000 0 3 1.000 9 5 1 .167 3 4 .571 10 1 0 .000 0 2 1.000 £ 33 £ 2 X~.067 £ 1 2 £ 3 7 X . 7 7 4 68 Table XXI. Frequencies and Proportions of Paired Disap-pearances With and Without Auditory Perceptual Experience Presentation. S Target PPL (No Training) Target GGR (Training) •Rale (m seconds) z Number Number Proportion Number Number Proportion JclerrticaJ Tra in ing TrainiWd Identical Trainivi^ T r a w i n c j Pairs Pairs P a i r s Pairs PairvS P a i r s 1 3 0 .000 5 4 .444 2 8 0 .000 2 7 .778 3 2 0 .000 0 1 1.000 4 7 1 .125 3 4 .571 5 12 3 .200 6 14 .700 £32 £4 X.045 1 3 0 .000 2 4 0 .000 3 9 0 .000 4 6 0 .000 5 3 0 .000 £25 £ 0 ~>f.ooo 1 7 2 .222 2 10 2 .167 3 3 1 .250 4 4 0 .000 5 3 0 .000 £ 27 £ 5 IT. 128 £16 ^30 X.699 2 1 .333 5 8 .615 0 2 1.000 0 7 1.000 3 5 .625 £10 £ 2 3 IT. 715 3 9 .750 5 9 .643 2 5 .714 1 8 .889 1 2 .667 £12 £33 X\733 69 Table XXI (Continued) 1 7 1 .125 2 3 .600 2 9 1 .100 1 5 .833 3 6 0 .000 0 5 1.000 4 6 1 .143 1 11 .917 5 5 0 .000 0 7 1.000 £ 3 3 £ 3 ^T.074 £ 4 £ 3 1 7". 870 1 7 4 .364 3 6 .667 2 5 4 .444 6 3 .333 3 7 0 .000 3 4 .571 4 3 0 .000 3 2 .400 5 7 1 .125 6 2 .250 £.29 £_9 Y. 187 £ 2 1 £ 1 7 T . 4 4 4 1 5 0 .000 1 7 .875 2 4 0 .000 1 5 .833 3 15 2 .118 4 12 .750 4 3 3 .500 3 5 .625 5 5 1 .167 7 4 .273 £ 32 £ 6 T . 1 5 7 £ 1 6 £ 3 3 X~.671 The task during the t r a i n i n g period was looking for s p e l l i n g e r r o r s . The task during the t r a i n i n g period was counting l e t t e r s . 7 0 Training Words used i n Experiments I C f II and I I I DEGREE EGRET AGREE EGRAB UGRAD GRADE GRADIENT GRAIL INGRAM GRAM GRANITE GRAND GRANT GRANULE GRATIFY ENGRAVE GRAVEL GRAVID GRAZE GREBE GREEDY GREEK GREEN DISGRID GRILL GRIME GRIND GRIT GROAN GRIZ GROAT INGRED GROIN GROOM GROVE GROTTO GROWL GRUB GRUEL GRUM HYGRO LOGRO MEGRIM MIGRANT NEGRO NEGROID NIGRIFY OGRE TIGRINE VAGRANT ENGRAFT INGRAIN INCONSR CHAGRE TINGRE MIS&RAD SPEGRED PONGRA GRAVITY SPAGRI 71 GRIFT GRONS AGRONOMY AGROUND DEGRADE SQRADATION GRADUALLY GRADUATE TELEGRAM UNGRAMMATICAL GRANDCHILD GRANULATED GRATICULATION GRATUITY HANDGRENADE FAGRIEVED GRIMACE INGREDIENT BEECHGROVE MIGRATION NEGROPHOBIA CONGRATULATE UNGRACEFUL ANTIGRAVITY CONGRUENT TACHOGRAM TELECTOGRAM VINAIGRETTE XYLOGRAM AGRICULTAL SOGREOUS SEGREANT ESPLAGRADE SGRENOID SPELLGROUND SPEGRULATE UNGRATEFUL INGRATITUDE GRIZZLY INCONGRUITY 72 Control Words used i n Experiments I C, II and I I I ABAFT ABODE BEFOUL BLAK BOMB BOULT CLEAVE DEMON DAILY DEVAL ELECT FULL HIND HILT HOE KNIT LEAN LIMEN MELLOW MEDLE MAIN NEED NET ONYX OVAL OWL TABLE TACKLE LYNCH MANIA BEECH NAVY QUEEN DUEL DUKE BENZOL TATTOO TEAF WAIL WAHOO ABANDON ABILETY ALCAHOLIC BEATLE BINOMIAL CANUCK CLIMBD DECIMAL DIAMOND DADDIE EXHALE INCLUDE INCIDENT FITFUL KNACK LANDED LATENT LAWFUL LEX IC ONE MELODY 73 HACKNEYED METABOLIC MILLED NOODLE NUMT OOKNIK OVATION TAKE TAMALE MAKE MANTLE NEUTER ONLY QUANTUM FINE EVIN TANDEM WAIVE WALKED WAYLAID WAXE ZANY YULE YOUTH YIELD LUCID INFINITY BELT ALLOW ACETANE BABOON BABBY CLAY DEUTON EXECUTE FELLOW HOMICIDE SPINACH DESPITE TOWARD 74 Control numbers used i n Experiment I A 47 141 441 671 197 691 764 497 674 417 619 1467 4679 6791 7914 9146 1146 4469 7711 9941 9764 7641 6419 4197 1976 9976 7764 6641 4419 1197 4769 6916 7466 7971 6749 7641 1946 1146 1417 4146 6461 7441 1191 4697 9461 7674 14671 46791 16791 17914 91461 11464 44671 77114 99414 97641 76417 76419 41976 19761 74661 17971 67419 76497 767447 946114 469741 119167 744119 646176 414617 141719 114617 194661 764111 4146791 6461411 7441646 1946764 6749146 7971664 141461 7441416 7674476 4679111 11914697 94614697 46971197 74761197 46714671 197611764 764179941 446719146 467911191 75 T r a i n i n g N u m b e r s u s e d i n E x p e r i m e n t I A 85 32 485 854 857 859 185 851 685 856 785 985 132 321 432 324 632 326 732 327 932 329 8532 4854 7857 9859 8544 1685 1854 6857 6859 6685 6985 1321 4327 6632 9932 3277 1324 4326 3269 6324 13285 32851 63285 85326 327^85 93285 85324 32854 13211 85632 14856 85174 61859 17329 73241 185132 326856 132185 632685 851321 853277 132985 851432 853219 185632 485632 485327 432851 326854 413285 6327851 7132851 8563211 4324856 1185632 3217461 8516321 4132851 1851732 4328514 32468511 14785132 32146851 16785132 13279851 85132411 17851646 85179132 41326714 64327185 985413241 856974321 932146851 485732614 763248516 785614132 732418564 132857494 

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