Perceptual conditions of association: A possible confounding

IOURNAL OF VERBAL LEARNING AND VERBAL BEI:IAVIOR I, 214-217 (1962)

Perceptual Conditions of Association: A Possible Confounding GEOFFREY

KEPPEL

Department oJ Psychology, Northwestern University, Evanston, Illinois

In a series of systematic experiments, Asch, Ceraso, and Heimer (1960) explored the role of Various perceptual conditions obtaining between elements of a figure and the subsequent joint recall of the elements. These experiments and findings may best be described by use of Fig. 1 as an example. The drawings labeled "Unitary" (U) and "NonUnitary" (NU) correspond to the two types of figures with which Asch et al. are concerned. I t will be noted that both drawings contain two main aspects, the square and the X's, described by Asch et al. as the form and the mode, respectively. The U figure combines form and mode in such a way that the form (square) requires the spatial arrangement of the mode ( X ' s ) for its contour or shape. The N U figure, on the other hand, relates form and mode merely by spatial contiguity, the square drawn in continuous line on the left and the form extended in a line to the right. In the basic experiment of Asch et al., e.g., Exp. 1, one group of Ss was presented a series of ten U stimuli while the other was presented a corresponding series of ten N U stimuli, followed by a free-recall test in which S attempted to recall together the appropriate forms and modes of the respective figures. In terms of the percentage of the total recall given as correct pairings of form and mode, a highly significant difference was obtained in favor of the U condition (i.e., 76.2% v. 4 9 . 2 ~ ) . The remainder of the experiments reported by Asch et al. that were concerned with this effect (Exps. 1-10) confirmed these basic findings with various methods of recall and testing. The superior recall of form and mode correctly paired under the U condition was in-

terpreted by Asch et al. as being the result ot the perceptual dependency of the form and the mode; that is, the "structural interdependence" of form and mode facilitated the correctness of pairing. The inferior perform. ance of the Ss receiving the N U stimuli was attributed to the relative independence of form and mode, each of which are members of separate heterogeneous figures. These findings were taken by Asch et al. as demonstrating that the traditional associationists have neglected the perceptual conditions of association, for it is with the N U stimuli that the associationists have been exclusively concerned. I t was felt that the processes postulated by association theory are unable to account for the findings of these experiments. It was recognized by Asch et al. that before acceptance of their perceptual interpretation, "it is n e c e s s a r y . . , to establish whether stimulus properties other than those we have identified might have been responsible for the findings" (p. 30). One such possibility suggested by Asch et al. considered the amount of information to be learned under the two conditions. From a strict interpretation of what is described as "unitary," it is obvious that U stimuli require recall of a single formmode combination while the N U stimuli involve recall of two such form-mode combinations, the form and mode of the figure on the left (square and continuous line, respectively), and the form and mode of the modal display on the right (straight line and M's, respectively). The higher joint recall of form and mode for the U stimuli, then, would be the result of a smaller amount of material to be learned relative to the N U stimuli. Asch et al. handled this possible objection by refer214

PERCEPTUAL CONDITIONS OF ASSOCIATION ring to the c o m p a r a b l e total recall ( c o r r e c t and i n c o r r e c t pairings, and the s e p a r a t e recall of f o r m a n d m o d e ) scores for the two groups, and to the fact t h a t Ss h a d full knowledge of the c o n s t r u c t i o n of the stimuli so t h a t the a d d i t i o n a l aspects of the N U stimuli were irrelevant. H o w e v e r c o n v i n c i n g these a r g u m e n t s m a y be, the m o s t a d e q u a t e test w o u l d seem to t a k e the f o r m of a p p r o p r i a t e control conditions. Such an a t t e m p t is to be r e p o r t e d here. I n the p r e s e n t e x p e r i m e n t an a t t e m p t was m a d e to m a k e the " t w o n e s s " of the U and IN~U stimuli the s a m e a n d thus e q u a t e the a m o u n t to be l e a r n e d u n d e r the two conditions. I n order to control for " t w o n e s s " a n d still m a i n t a i n " u n i t y " as defined b y Asch et al., the m o d a l d i s p l a y of the N U s t i m u l u s was s i m p l y a d d e d t o the original U s t i m u l u s ; an e x a m p l e of the u n i t a r y - c o n t r o l ( U C ) s t i m u l u s appears in the b o t t o m p a n e l of Fig. 1. Since t h e r e p r e s e n t a t i o n of the m o d e to the r i g h t of the U s t i m u l u s w o u l d a p p e a r to c o n s t i t u t e r e d u n d a n t m a t e r i a l , no additional i n f o r m a t i o n was a d d e d to the s t i m u l u s b y this control, a n d since the basic r e q u i r e m e n t t h a t f o r m and m o d e be d e p e n d e n t u p o n each o t h e r for the U s t i m u l u s was m a i n t a i n e d as far as can be d e t e r m i n e d f r o m the specifications given b y Asch et al., the correct pairing of f o r m a n d m o d e for the U C stimuli should be c o m p a r a b l e to t h a t r e p o r t e d for the U stimuli. METHOD

Stimuli. Ten stimulus figures used previously (Asch et al., Exp. I, Fig. 2) were transcribed onto sheets of 8 ~ X 5 ~ in. paper. The figures were approximately 2-in. square, the form and mode being separated by approximately ~ in.; the representation of the mode was about I ~ in. in length. The U and NU stimuli were identical to those employed by Asch et al., while the UC stimuli combined the U stimulus with the NU modal display (see Fig. 1). The three different stimuli constituted the three conditions of the present study. For each of the three conditions the 10 stimuli were randomly ordered and combined into booklets, together with two blank sheets of paper which served to mask the first stimulus. Each S received a different booklet and hence a different random ordering of the stimuli.

XXXXXX X X X X XXXXXX

X × X X

215

UNITARY (U)

NON-UNITARY (NU) XXXXXX

XXXXXX X X X X XXXXXX

× X X X

UNITARY-CONTROL

(UC)

XXXXXX

FIo. 1. An example of the stimuli employed in the present experiment. See text for explanation of the figures in the three panels.

Procedure and Subjects. The procedure of Asch et al. was adapted for group administration. At the start of the experiment, Ss were handed stimulus booklets and 12 sheets of blank paper. Instructions were given to the effect that S was to study each stimulus for a period controlled by E's spoken signal, following which a test of free recall of the figures would be given. Since a random sample of Ss for each condition separately was not obtained, the three conditions were randomly assigned to each group of Ss. As a consequence of this assignment the nature of the three sets of stimuli was described to all Ss by having the three stimuli of Fig. 1, which would not appear in the stimulus series, drawn on a blackboard, the understanding being that S would receive only one type of stimulus during the study period. No information was given with regard to the differences in the stimuli other than the fact that the figures were to be recalled exactly as they had appeared in the test booklets. The duplication of the mode in the figure on the left and the line on the right for the UC stimuli was not specifically mentioned since the experimental problem under consideration was the control of the "twoness" of the NU stimuli relative to the U stimuli. After answering questions, E signaled the passage of successive 5-sec. intervals to control the rate of S's self-presentation of the stimuli. Following stimulus presentation, the booklets were collected and instructions given for free recall in which Ss were asked to draw the figures exactly as they had appeared, in

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KEPPEL

any order, and to guess at features of which they were not sure. The Ss were allowed 5 min. to recall the stimuli. In the original design of the experiment UC and NU stimuli were presented to 15 and 17 Ss respectively. A subsequent replication included the U stimuli as an additional condition so that in this replication the three conditions, U, UC, and NU, were given to 15, 14, and 14 additional Ss, respectively. Since the Ss in the UC and NU conditions of these two subexperiments were treated identically and produced essentially the same results, the data are combined in the presentation of the results. Thus, the total number of Ss in the U, UC, and NU conditions becomes 15, 29, and 31, respectively. The Ss in both experiments were drawn from students taking undergraduate pzychology courses at Northwestern University. None of the Ss was familiar with the experiments of Asch et al., nor of the purpose of the experiment. Scoring. The free-recall reproductions were scored by the method followed by Asch e t a / . (p. 6) in which stimulus recall was categorized into four response categories. The first two categories consisted of a correct form and a correct mode recalled together, the first case being a perfect recall, i.e., the recall of form and mode correctly paired, the second case being the recall of a form and a mode appearing in the stimulus series but being incorrectly paired in recall. The last two categories consisted of separate recalls of either form or mode. For example, the recall of a form was scored as a separate recall if it was recalled alone, or with a mode not appearing in the series, or with a mode which was previously given in recall. The same procedure was followed for the separate recall of a mode. In this manner all correct recalls were exhaustively placed in one of the four response categories. The total recall score for an S consisted of a summation of each correct reproduction, the recall of a form or mode separately receiving a score of 1 and a recall of a correct form and mode together (both correct and incorrect pairings) receiving a score of 2. By

this manner of tabulation the number of units scored in each category was equated. RESULTS AND DISCUSSION

The means and percentages of the total recall for the four response categories are presented in Table 1. The comparisons of main interest are to be found in Column 1 of Table 1 where the percentage correct pairings for the three groups are listed. The comparison between U and N U stimuli reveals values of 72.54% and 41.22% for U and NU, respectively; a Mann-Whitney test indicated this to be a highly significant difference ( P ~ .001). These percentages compare q u i t e f a v o r a b l y w i t h t h o s e of A s c h et al. ( 7 6 . 2 % a n d 4 9 . 2 % for U a n d N U , respect i v e l y ) , so t h a t t h e d u p l i c a t i o n of t h e b a s i c p h e n o m e n o n is n o t in d o u b t . C o m p a r i s o n of t h e j o i n t recall of t h e U C a n d N U s t i m u l i will a l l o w d e t e r m i n a t i o n of t h e e x t e n t of t h e " u n i t a r y effect" w h e n t h e a m o u n t of m a t e r i a l p r e s e n t e d to t h e two g r o u p s is c o n t r o l l e d . I n s p e c t i o n of C o l u m n 1 r e v e a l s a v a l u e of 4 6 . 7 8 % for t h e U C c o n d i t i o n , a v a l u e w h i c h differs s i g n i f i c a n t l y f r o m t h a t o b t a i n e d for the U condition (P z .01), while the 5.56% difference b e t w e e n U C a n d N U w a s n o t sign i f i c a n t ( P ~ .05). I t is clear, t h e n , t h a t t h e g e n e r a l f i n d i n g s of A s c h et al. a r e r e p l i c a t e d by the present experiment, but that the c o n t r o l c o n d i t i o n h a s l o s t t h e " u n i t a r y effect," p r o d u c i n g r e s u l t s c o m p a r a b l e to t h o s e o b tained under the NU condition. T h e t o t a l recall l i s t e d in C o l u m n 5 is a p p r o x i m a t e l y o n e i t e m h i g h e r for b o t h U a n d N U t h a n t h a t r e p o r t e d b y A s c h et al. ; t h i s m a y b e d u e to t h e 1-sec. slower p r e s e n t a t i o n e m p l o y e d i n t h e p r e s e n t e x p e r i m e n t . I t will

TABLE 1 FREE-RECALL SCORES OF UNITARY, UNITARY-CONTI~OE,AND NoN-UNITARY S~w~LI

Stimuli

N

1

2

3

4

5

Correctly paired recall

Incorrectly paired recall

Form recall alone

Mode recall Mone

Mean of total recall

Unitary

15

M %

8.27 72.54

1.33 11.67

1.13 9.91

0.67 5.88

11.40

Unitary-Control

29

M %

4.28 46.78

2.28 24.92

1.90 20.76

0.69 7.54

9.15

Non-Unitary

31

M %

4.39 41.22

3.61 33.90

1.94 18.22

0.71 6.67

10.65

PERCEPTUAL CONDITIONS OF ASSOCIATION

be noted that the total recall of the UC group is considerably lower than that of either the U or N U groups. An analysis of variance of the total recall scores produced significant variation (F---- 5.17, d]-~- 2/72, P < .01) ; a Duncan multiple range test for unequal replications revealed the UC group to be significantly lower than the U group (P<.01) and the N U group (.01 < P < .05), while the means of the latter two groups not to differ significantly (P > .10). The deficiency of the UC condition in total recall appears to be attributable to the category of incorrectly paired recall since, relative to the N U condition, mean recall is equivalent for the three remaining categories. This comparison would imply a close correspondence betwen UC and N U conditions, at least with regard to all classifications of response except incorrect pairings. The logic of the present experiment was to .equate the U and N U conditions employed by Asch et al. with regard to the number of configurations which must be studied and recalled, without a change in the basic unitary relationship between form and mode. The results of the present experiment show that by controlling "twoness" through the use of the UC stimuli correct joint recall of form and mode was reduced to levels corresponding to those obtained for the N U stimuli. The argument may be raised that the modal line of the UC stimulus may not have constituted completely redundant material when compared with the U stimulus; that is, S may not have been aware that the mode to the right was completely redundant. I t was felt that mention could not be made of the redundant nature of the UC stimuli at the start of the experiment since it seemed important to maintain a continuity in the instructions for the three sets of stimuli and the conditions of Asch et al. However, inspection of the recall sheets for the Ss in the UC condition revealed that most of the Ss were aware of the repetition of the mode to the right, since 92% of all reproductions produced by the UC group were in the appropriate format, i.e., a line to the right drawn in the same mode as the form to the left. I t is evident, then, that in spite of S's awareness of

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the redundant nature of the UC stimuli, the necessity of attending to two stimuli instead of one markedly reduces the unitary effect reported by Asch et al. In discussing several alternative explanations of their experimental findings, Asch et al. recognized the interpretive problem that would result if one of their seven alternative interpretations were shown to be applicable to their experiments: " H a d we demonstrated that these other conditions [such as amount to be learned] could account for the results, the significance of the investigation would have shifted appreciably" (p. 32). I t is possible that the assumption made here that U and UC stimuli are both "unitary" will not be accepted by Asch et al. However, if the U and UC stimuli are judged to differ in "unity," a more precise specification of this stimulus characteristic must be made so that other experiments may be designed to evaluate the perceptual conditions of association. SUmmArY Asch, Ceraso, and Heimer (1950) compared the free recall of two types of figures, unitary (U) and non-unitary (NU). The former consisted of a series of single figures drawn with distinctive outlines or modes, while the latter consisted of the same figures except that the shape or form was drawn in continuous line and the pattern of the outline displayed to the side of the figure. The joint recall of form and mode was superior for the U stimuli. The present experiment replicated the U and N U conditions, adding a control group which received the U stimuli and the pattern display to one side of the form. This was done to make the "twoness" of the U and UN stimuli the same. That "twoness" of the N U stimuli appears to be critical in producing the original "unitary effect" was shown by the fact that the U-NU difference disappeared when the control stimuli were recalled. These findings provide an alternative explanation of the findings of Asch et al. REFERENCE

ASCIi, S. E., CERASO, J., AND HEII'CIER, W. Perceptual conditions of association. Psychol. Monogr., 1960, 74, No. 490. (Received July 25, 1962)