Stimulus, response, and reward contiguity in pattern discrimination by children

JOURNAL

OF EXPERIMENTAL

Stimulus,

RICHARD

CHILD

PSYCHOLOQY

6,556-562

Response, and Pattern Discrimination A.

WUNDERLICH, The

Catholic

JEAN

(1968)

Reward Contiguity by Children NAZZARO,

University

of

AND

JAMES

in

YOUNISS

America

Eighty fourth-grade children discriminated patterns when cues were located either on the periphery or center of stimulus cards and when spatial contiguity between stimulus and response, and stimulus and reward was systematically varied. Discrimination was easier when peripheral cues rather than center cues were relevant, and also when stimulus-response contiguity rather than discontiguity was presented. These results complemented those of younger children and lower primates and are discussed in the context of attention theory.

A basic tenet in traditional learning theory holds that stimulus (S), response (R), and reward (Ed) contiguity influence the rate of acquisition of even elementary discriminations. It is not surprising then that at least a dozen studies with lower primates have consistently demonstrated impaired acquisition when S and R were spatially discontiguous compared with conditions when they were located together (cf. Meyer, Treichler, and Meyer, 1965). In studies of children’s discrimination the effects of S-R-Rd spatial contiguity have not been so well established. While observations of nursery school children (Jeffrey and Cohen, 1964) confirm the S-R discontiguity effect found with lower primates, reports on older children’s performance are equivocal. Wunderlich and Iorio (1966) observed nondifferential rates of acquisition between a condition that spatially separated S and R and another in which S-R were spatially contiguous. They used a tactual discrimination problem with children of CA 9. This result is compatible with related observations of Perkins, Banks, and Calvin (1954) that discrimination was not impeded for children of CA 9-10 when S and R were separated temporally compared to their contiguous presentation. Taken together, data from these three investigations might suggest that the effect of contiguity might be systematically related to an age variable. One other study by Murphy and Miller (1959) with children is of particular interest. After sampling children from grade one through four on a visual discrimination under two conditions of S-R contiguity, they 556

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reported that children younger than CA 9-10 failed to solve the discrimination within 400 trials when S and R were spatially separated. Older children (CA g-10), on the other hand, learned the same problem in fewer trials than the younger and additionally learned the program even faster when S and R were contiguous. Since Murphy and Miller employed as the discriminative cue a diagonal-right and diagonal-left pattern-a discrimination which appears extremely difficult for young children even when simple diagonal lines are used (Rude1 and Teuber, 1963)-it is not clear whether their age-related effect was due to spatial discontiguity or to the complexity of the discriminative cue. In order to provide clearer evidence on discrimination as a function of spatial contiguity in children the present experiment was designed. Contiguity among S, R, and Rd was manipulated systematically in a manner similar to Jeffrey and Cohen’s (1964) design but three important changes were made. First, children of CA 9-10 served as Ss, a range in which ambiguous results were previously obtained. Second, patterns rather than solid-color patches were used as the discriminative cue since pilot data indicated that acquisition proceeded too rapidly to detect possible effects with nonpattern cues. Finally, within the patterns contiguity between X and R was varied by positioning the discriminative cue on either the center or the border of a card. Research with the lower primate (Riopelle, Wunderlich, and Francisco, 1958; Wunderlich and Dorff, 1965) has shown distinctive differences in performance on problems of this type. METHOD

Subjects Eighty fourth-grade children served as Ss. All Ss achieved at least an MA of 9 years on the Peabody Picture Vocabulary Test. The 38 boys and 42 girls used were experimentally naive. Apparatus The test apparatus was similar in principle to the Wisconsin General Test Apparatus. It presented a neutral gray test tray within a framework from which an opaque screen could be lowered to conceal test stimuli from S’s view during baiting. The test tray contained two channels in which reward wells, spaced 12 inches at centers, were countersunk. Clear plastic holders fitted flush into the channels of the test tray 2nd could be easily slid forward by S in making a response. The holders were dumbbell-shaped, containing a stimulus plaque at one end and a solid gray plaque at the opposite end. Two 4-inch-long strips of plastic joined the two ends. The strips were 1.5 inches apart, permitting exposure of

558

WUNDERLICH,

NAZZARO,

AND

YOUNISS

0 C-l

C-Z

c- 3

c-4

c- 5

C-6

C-7

C-S

1. Schematic presentation of the stimulus configurations and experimental conditions. Border cues and center cue problems are alternately illustrated under four conditions of S, R, and Rd contiguity. Plus signs denote contiguity; ellipses, discontiguity. Arrows indicate direction of movement from subjects, and circles represent uncovered reward wells after response. FIG.

reward wells in four of the experimental conditions as illustrated in Fig. 1. The stimulus plaques were constructed of white matboard and colored construction paper. They measured 3 inches on edge and contained either a .75-inch colored border or a colored center displaced .75 inches from each edge. The stimulus plaques were inserted into one end of the plastic dumbbell-shaped holder while a a-inch square of gray construction paper was inserted into the opposite end. The gray square served as a response plaque in some experimental conditions as described in the procedure. Design and Procedure Eight independent experimental conditions were used. Essentially, four of the eight conditions were replicates in that they presented the same contiguity conditions of the other four, differing only in the type of pattern employed. As illustrated in Fig. 1, C-2, C-4, C-6, and C-8 employed center cue patterns in which the color cue was located three quarters of an inch from each edge. Border cue patterns were used in C-l, C-3, C-5, and C-7. In C-l and C-2 the S and Rd were spatially contiguous but spatially separated from the gray plaque to which R was made. In C-3 and C-4, the Rd was found beneath the response plaque and both R and Rd were spatially separated from S. In C-5 and C-6, R was made to the stimulus plaque thus presenting S-R contiguity, but Rd was spatially discontiguous from both. Finally, C-7 and C-8 presented S-R-Rd contiguity, the Rd being beneath S to which R was made.

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Subjects were instructed to find tokens that could be accumulated and later traded for candy or a toy selected prior to testing. During instructions, both wells were baited, but the stimulus holders were empty. The E demonstrated where R was to be made, displacing one holder and removing the token; the child then tried with the other holder. The discrimination trials presented the child two stimuli in the plastic holders, one on each track. The plastic holder on one end of each dumbbell held the square gray patch; the holder at the other end contained the stimuli to be discriminated. The stimuli appeared either in the holders nearest S or at the other end depending upon the experimental condition (cf. Fig. 1). The child always pushed the plastic holder nearest him; thus, when S and R were contiguous, he actually responded by pushing the plaque holding the stimulus. When they were not contiguous, he responded to the holder containing the gray paper, the stimulus cards being held in the holders at the far ends of the two dumbbells. Pushing either dumbbell uncovered either of two reward wells, one under the near holder or one under the far holder, depending upon the experimental condition. When R and Rd were contiguous the baited well was the near well under the holder that S pushed. When they were not contiguous, the baited well was under the far holder at the other end of the dumbbell. It should be noted that under conditions of S-R contiguity, when the discriminative cue was the color on the border of the stimulus pattern, the child touched the discriminative cue when he responded. In center cue problems the response was touching the white border. When the child was to discriminate colors on the border or center under S-R discontiguity, he, of course, responded to the holder containing the gray patch. During testing, a Gellermann series determined the position of the positive stimulus of the five color pairs used, A criterion of 18 correct out of 20 consecutive responses or a maximum of 100 trials was used. RESULTS Mean error scores for each experimental group are presented in Fig. 2 where, with one exception, border cue problems are shown to result in fewer mean errors than center cue problems. An analysis of variance performed on the number of errors to criterion made by each group resulted in an F of 4.21 (df = l/72, p < .05) for the comparison of border cue and center cue problems, thus statistically supporting the differences observable in Fig. 2. One other F test was significant in the analysis of error scores. A significant main effect (F = 5.04, df = l/72, p < .05) was found for the difference between groups presented with S-R contiguity and groups in

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NAZZARO,

ASD

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Mean errors of eight experimental conditions of both border cue (B) and c-enter cue (C) type problems. Plus signs denote contiguity between S, R, and Rd while an ellipse denotes discontiguity. FIG.

2.

which discontiguity of S-R was imposed. No reliable effect for S-Rd contiguity was found nor were any interaction terms of the analysis significant. DISCUSSION

Under the conditions of the present experiment, it is clearly evident that children in the age range of 9-10 years are significantly impaired in learning pattern discriminations when S is spatially discontiguous with R. Regardless of whether a problem offered two stimuli that differed in color along their edges or contained color patches at their centers, if the children were required to respond by touching something other than the stimuli themselves, they made significantly more errors in learning the problem. This finding is compatible with that of Jeffrey and Cohen (1964) and extends the age range in which the contiguity effect may be found well beyond the nursery school-aged children used by them. That contiguity effects are notable in older as well as younger children whenever certain pattern discriminations are involved suggests that the agerelated effect reported by Murphy and Miller (1959) may have been determined largely by the type of discrimination problem they used. It is possible that the older children in Murphy and Miller’s study were able to learn a pattern discrimination with S and R discontiguous while younger children could not because the pattern effects were of varying degrees of perceptual difficulty for the two groups. The diagonal discriminations used by Murphy and Miller may have been simply too difficult for younger children and too easy for older children to be influenced by

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S-R contiguity. Given a more complex color pattern and separating S and R increases the probability that older children will, as younger children, have difficulty in making discriminations. That the type of pattern discrimination is of importance in determining problem difficulty is supported by the border cue-center cue difference noted in the present study. Center cue problems were significantly more difficult than border cues for the children used in the study and in this regard they are consistent with lower primates of several experiments (Meyer, Polidora and McConnell, 1961; Schuck, Polidora, McConnell, and Meyer, 1961; Wunderlich and Dorff, 1965). Both the S-R contiguity effect and that of border cue-center cue are readily understood within the framework of attention theory. Wyckoff (1952) originally proposed that the probability of observing responsesacts that result in the exposure of discriminable cues-critically determines the rate of discrimination learning. Wunderlich and Dorff (1965) have since evoked this concept to account for both contiguity and pattern effects in lower primate learning and it may be extended here to explain the similar results of 9 -and lo-year-old children. The basic assumption is that children, like monkeys, look where they touch. Thus, the probability of observing the appropriate discriminable cues of the present problem is higher when children are permitted to touch the actual cue (S-R contiguity) than when they respond remotely from the cue (S-R discontiguity). Likewise, if children move a stimulus plaque by the edges as monkeys characteristically do, they touch the discriminable cue in a border cue problem but not in a center cue one. While no systematic observations were made of where the children actually touched in border cue-center cue problems, Schuck (1960) has shown that cues located only three-fourths of an inch from the response site as in the center cue problems of the present study deter learning. The lack of any reliable differences among conditions in which S and Rd were separated and those in which the two were spatially contiguous is not remarkable. Jeffrey and Cohen have found no effect of reward placement in relation to discriminative cues on learning of young children and other studies (Murphy and Miller, 1958; Wunderlich and Dorff, 1965) confirm this negative result with monkeys as well. REFERENCES JEFFREY, W. E., AND COHEN, L. B. Effect of spatial separation of stimulus, response, and reinforcement on selective learning in children. Journal of Experimental Psychology, 1964, 67, 577-580. MEYER, D. R., POLIDORA, V. J., AND MCCONNELL, D. G. Effects of spatial S-R contiguity and response delay upon discriminative performances by monkeys. Journal of Comparative and Physiological Psychology, 1961, 54, 175177.

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D. R., TREICHLER, F. R., AND MEPER, P. M. The formboard and related test techniques. In Schrier, A. M., Harlow, H. F., and Stollnitz, F. (Eds.), Behavior of nonhuman primates. New York: Academic Press, 1965. MURPHY, J. V., AND MILLER, R. E. Effect of the spatial relationship between cue, reward and response in simple discrimination learning. Journal of Experimental Psychology, 1958, 56, 2631. MURPHY, J. V., AND MILLER, R. E. Spatial contiguity of cue, reward and response in discrimination learning by children. Journal of Experimental Psychology, 1959, 58, 485489. PERKINS, M. J., BANKS, H. P., AND CALVIN, A. D. The effect of delay on simultaneous and successive discrimination in children. Journal of Experimental Psychology, 1954, 48, 4X-418. RIOPELLE, A. J., WUNDERLICH, R. A., AND FRANCISCO, E. W. Discrimination of concentric ring patterns by monkeys. Journal of Comparative and Physiological Psychology, 1958, 51, 622-626. RUDEL, R. G., AND TEUBER, H. Discrimination of direction of line in children. Journal of Comparative and Physiological Psychology, 1963, 56, 892-898. SCHUCK, J. R. Pattern discrimination and visual sampling by the monkey. Journal. of Comparative and Physiological Psychology, 1960, 53, 251-255. SCHUCK, J. R., POLIDORA, V. J., MCCONNELL, D. G., AND MEPER, D. D. Response location as a factor in primate pattern discrimination. Journal of Comparative and Physiological Psychology, 1961,54, 543-545. WUNDERLICH, R. A., AND DORFF, J. E. Contiguity relationships of stimulus, response, and reward as determinants of discrimination difficulty. Journal of Comparative and Physiological Psychology. 1965,59, 147-149. WUNDERLICH, R. A., AND IORIO, V. The observing response and spatial contiguity in tactual discrimination learning of children. Proceedings of the Am&cam PsyMEYER,

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