Ambiguous-cue learning in preschool children: A test of the dimensional characteristics of task stimuli

JOURNAL

OF EXPERIMENTAL

CHILD

PSYCHOLOGY

33, 405-412 (1982)

Ambiguous-Cue Learning in Preschool Children: A Test of the Dimensional Characteristics of Task Stimuli WILLIAM

N. BOYER AND CHAD PAGE Colorado

State

University

Sixteen preschool children were administered a two-choice discrimination problem consisting of three stimulus compounds: the consistently rewarded stimulus, the consistently nonrewarded stimulus, and the ambiguous stimulus which was nonrewarded when paired with the positive, but rewarded when paired with the negative. When both pair of stimuli, positive-ambiguous and negative-ambiguous, were presented together the subject was required either to choose or to avoid the ambiguous stimulus depending upon the stimulus with which it was paired. In Experiment 1, when each of three stimuli (positive, negative, ambiguous) varied along one nonspatial cue dimension (color), performance was better on negative-ambiguous trials than positive-ambiguous trials. In Experiment 2, when the positive and negative stimuli varied along three nonspatial cue dimensions (colors and form) and the ambiguous stimulus varied along one of these dimensions (color), superior positive-ambiguous over negative-ambiguous performance was obtained. These findings complement those reported for other subjects and confirm Berth’s (D. B. Berth, Learning and Motivation, 1974, 5, 135-148) predictions regarding use of differential numbers of cue dimensions.

The ambiguous-cue problem consists of a learning task in which three stimuli are presented over a series of two-choice trials. The stimuli are: the positive stimulus which is consistently rewarded, the negative stimulus which is consistently nonrewarded, and the ambiguous stimulus which is rewarded when paired with the negative but nonrewarded when paired with the positive. The two resuiting pairs of stimuli, positiveambiguous and negative-ambiguous are alternated randomly to produce a discrimination problem in which the critical question is whether performance is better on positive-ambiguous or negative-ambiguous trials. When stereometric “junk” objects are employed as stimuli with both human (first grade children, retardates) and nonhuman (primate) subjects, negative-ambiguous performance is significantly better than positive-ambiguous performance (Boyer, Polidora, Fletcher, & Woodruff, 1966; Fletcher & Garske, 1972; Fletcher, Grogg, & Garske, 1968; Leary, 1958; Requests for reprints should be sent to W. N. Boyer, Department of Psychology,colorado State University, Fort Collins, CO 80523. 405 0022~0965/82/30405-08$02.00/O Copyright Q 1982 by Academic Press, Inc. All rights of reproduction in any form reserved.

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Zeaman & House, 1962). While most experiments of the ambiguous-cue problem have used stereometric objects, some have employed planometric plaque stimuli. Researchers using planometric stimuli with primate subjects have reported positive-ambiguous performance to be consistently better than negative-ambiguous performance (Boyer & Polidora, 1972; Boyer et al., 1966; Fletcher & Bordow, 1965; Thompson, 1954). This result is exactly the opposite to that reported for stereometric objects. However, Boyer and Polidora (1972) have shown that the contrasting results can be attributed to the type of the stimuli used. For instance, when the plaque form of the problem uses a blank (white) ambiguous stimulus and the positive and negative stimuli contain additional cues such as colored stripes, orientation of stripes, performance is better on positive-ambiguous than negative-ambiguous trials. On the other hand, experiments that have used planometric stimuli which contain a distinctive ambiguous stimulus have produced the negative-ambiguous over the positive-ambiguous result with primates (Boyer & Polidora, 1972) and pigeons (Hall, 1980; Richards, 1973) as subjects. The purpose of the experiments reported here was: first, to test subjects (preschoolers) not previously tested on the ambiguous-cue task; second, to empirically test Berth’s (1974) recent theoretical analysis of performance in this relatively complex task. Berth’s treatment is based on simple conditioning principles and revolves around the number of cue dimensions contained in the stimulus compounds. Two basic predictions derived from Berth’s analysis are (a) that when the positive, negative, and ambiguous stimuli differ along the same number of nonspatial cue dimensions, negative-ambiguous performance will be superior to positiveambiguous performance, and (b) the greater the number of nonspatial components possessed by the positive and negative stimuli in relation to the ambiguous stimulus, the greater the probability of superior positive-ambiguous performance. EXPERIMENT 1 In Experiment 1, we attempted to determine whether the preschool child would show negative-ambiguous performance to be superior to positive-ambiguous performance when the positive, negative, and ambiquous stimuli (or compounds) differ along one nonspatial cue dimension (color). Method Subjects. Eight children (four male and four female) were drawn from the Colorado State University preschool, representing a relatively middle-class population. The subjects had a mean age of 53 months and ranged in age from 35 months to 67 months. None of the children had

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any known previous experience in discrimination learning or a task similar to the ambiguous-cue problem. Apparatus and stimuli. The apparatus consisted of a modified Wisconsin General Test Apparatus. During testing, the subject was separated from the Experimenter by a one-way mirror under which the Experimenter pushed the test-tray. The tray contained two receptacles, each covered with a stimulus. The apparatus was designed so that when the test-tray was pushed toward the subject the door below the mirror would rise, allowing the test stimuli to pass through toward the child and the door to lower. When the tray was withdrawn, the door would rise again allowing the tray to return to the Experimenter’s side of the apparatus and the door to lower again. This technique prevented the child from observing the Experimenter depositing the reinforcement in a receptacle for the next trial. Reinforcement consisted of a smiley face, a line drawing on a small circular piece of construction paper. The three stimuli (positive, negative, ambiguous) were constructed from 10.16 x 10.16-cm acrylic plastic squares and were colored blue, green, and yellow, respectively. Thus, each of the stimuli possessed the same number of nonspatial components (which in this case is one). Procedure. A modified version of the procedure used by Boyer, Bullock, and Viney (1971) was employed. Each child was tested individually in a small room adjacent to the preschool. The child was led into the room, seated in front of the apparatus and told they were going to play a game, the object being to win smiley faces. At the end of the game the smiley faces would be counted to see how well they did. The child was then shown the test-tray without the stimuli or reward and told that each time the tray was pushed through the divider there would be a card over both holes and a smiley face under one of the cards. The Experimenter then informed each child that they would have just one chance on each trial to find the smiley face by displacing one of the cards. If the chosen card covered a smiley face, the child would be allowed to retrieve it, thus accumulating smiley faces. If the chosen card did not cover a smiley face, the trail would terminate and the tray withdrawn. The Experimenter then returned to the other side of the apparatus and testing began. All subjects received four consecutive test sessions of 48 trials each. For each session, 24 trials were positive-ambiguous and 24 were negativeambiguous. All positive-ambiguous trials had a reward under the positive stimulus and no reward under the ambiguous stimulus, whereas, all negative-ambiguous trials had a reward under the ambiguous stimulus and none under the negative stimulus. For all subjects, the four possible presentations (positive-ambiguous, negative-ambiguous, ambiguous-positive, ambiguous-negative) were randomized within each block of four

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trials to control for possible position or order effect. In addition, to control for color preference, the three stimuli were randomly designated as the positive, ambiquous, and negative stimuli for each child. The intertrial interval was approximately 10 sec. Results and Discussion In Fig. 1, the percentage of correct responses is plotted for sessions of 24 positive-ambiguous and 24 negative-ambiguous trials for all subjects. The graph indicates that the preschool children clearly performed better on negative-ambiguous than positive-ambiguous trials. An analysis of variance was performed on the two within-variables negative-ambiguous, positive-ambiguous Trials and Sessions, and the one between-variable, Sex. The significant negative-ambiguous, positive-ambiguous Trial effect substantiates the above conclusion [F(l, 6) = 6.021; this and all subsequent statistical effects were considered significant if p < 0.05. There was also a significant Sessions effect [F(3, 18) = 7.151 indicating that improvement in learning was occurring on both negative-ambiguous and positive-ambiguous trials over test sessions. The interaction of negative-ambiguous, positive-ambiguous Trials and Sessions was also significant [F(3, 18) = 7.411; visual inspection of these data indicated that although there was an acquisition difference in favor of negative-ambiguous trials this difference increased over sessions. Simply stated, this interaction indicates that the rate of learning was greater for the negativeambiguous trials than positive-ambiguous trials in this experiment. Finally, there was no significant effect due to sex of child in the performance of the planometric problem.

gY L$o

50 I 2 3 4 SESSlONS OF 24 POSITIVE-AMBIGUOUS AND 24 NEGATIVE-AMBIGUOUS TRIALS

FIG. 1. Positive-ambiguous and negative-anbiguous trial performance when each of the positive, negative, and ambiguous stimuli contain one cue component.

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In this experiment, the positive and negative stimuli varied along three nonspatial cue dimensions (colors, form) while the ambiguous stimulus varied along a single nonspatial cue dimension (color). This manipulation tested the prediction that increasing the number of cue components to the positive and negative stimuli relative to the ambiguous stimulus would produce superior positive-ambiguous performance compared to negativeambiguous performance. Method Subjects. Eight children (five male and three female) from the Colorado State University preschool participated in this study. Their mean age was 60 months, ranging in age from 50 months to 69 months. Apparatus, stimuli, and procedure. The apparatus described in the previous experiment was used again. The three stimuli were composed of 10.16 x 10.16-cm acrylic plastic squares. The ambiguous stimulus was a blue color. The positive stimulus was a yellow colored plaque with a brown colored circle centered in the middle of it. The negative stimulus was colored green with a red colored triangle located in the middle of the plaque. These additional form cues were approximately equal in area (9 cm’). Half of the subjects received the positive stimulus as positive, the other half as negative. In accordance with Berth’s analysis, the nonspatial cues were assumed to be so dissimilar and distinctive from each other that no generalization occurred between them. The testing procedure was virtually identical to that of Experiment 1. Results

Figure 2 presents the percentage of correct responses for both positiveambiguous and negative-ambiguous trials as a function of sessions for all subjects. The graph illustrates that positive-ambiguous performance was superior to negative-ambiguous performance across all sessions. An analysis of variance revealed significant effects for type of Trial, [F(l) 6) = 10.971 and Sessions [F(3, 18) = 8.091. The Significant Sessions effect resulted from improvement over sessions of tesing. None of the interactions was significant and once again sex of child was not a significant effect (F’s < 1). GENERAL DISCUSSION Two experiments on the ambiguous-cue problem in the preschool child were carried out, which varied the number of cue components in the three stimulus compounds. Specifically, when the positive and negative

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NEGATIVE-AMBIGUOUS

SESSIONS OF 24 POSITIVE-AMBIGUOUS AND 24 NEGATIVE-AMBIGUOUS TRIALS

FIG. 2. Positive-ambiguous and negative-ambiguous trial performance when the positive and negative stimuli contain three cue components and the ambiguous stimulus one cue component.

stimuli contain the same number of nonspatial components as the ambiguous stimulus (Experiment 1) superior negative-ambiguous over positive-ambiguous performance was obtained. Similar results were reported by Boyer and Polidora (1972) who used three distinctively colored plaques and by Richards (1973) who used different colored key lights as stimuli. In Experiment 2, where the positive and negative stimuli varied along three nonspatial cue dimensions and the ambiguous stimulus varied along one of these dimensions, performance on positive-ambiguous trials exceeded performance on negative-ambiguous trials. This result is consistent with other experiments (e.g., Boyer & Polidora, 1972; Fletcher & Bordow, 1965) which employed positive and negative stimuli that were distinctively striped and colored, whereas, the ambiguous stimulus was left blank. Recently, a theoretical analysis has been proposed by Berth (1974) that can readily explain our results. Briefly, the analysis assumes that habit strength is conditioned directly to each component in the reinforced stimulus compounds and inhibition is conditioned directly to each component in the nonreinforced stimulus compounds. An additional assumption is that habit strength outweighs inhibition. In Experiment 1, where the positive and negative stimuli possessed the same number of cue components as the ambiguous stimulus, the amount of habit conditioned directly to the positive stimulus on positive-ambiguous trials and the ambiguous stimulus on negative-ambiguous trials is expected to be the same. Thus, the amount of generalized habit developing to the ambiguous stimulus on positive-ambiguous trials is equal to that built up to the positive stimulus. If we adopt the assumption that the probability of choosing the stimulus with the stronger effective habit is an increasing

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function of the difference between the habits of the stimuli, then the probability of selecting the ambiguous stimulus on negative-ambiguous trials should be higher than the probability of selecting positive over ambiguous on positive-ambiguous trials. In this way, we can account for the occurrence of the negative-ambiguous trial superiority. The same analysis can be extended to account for the pattern of results obtained in Experiment 2. Because the positive stimulus has more components than the ambiguous stimulus, the positive stimulus is expected to acquire a greater amount of conditioned habit than the ambiguous stimulus on negative-ambiguous trials. As a result, we can expect a minimal amount of habit to generalize from the ambiguous stimulus on negative-ambiguous trials to the ambiguous on positive-ambiguous trials. Combined with the inhibition conditioned directly to the ambiguous stimulus on positive-ambiguous trials, the resulting habit for the ambiguous stimulus is lower than that for the positive. Therefore, the probability of selecting positive over ambiguous on positive-ambiguous trials should be high and relatively better performance is expected in the positiveambiguous condition. It is also notable that a major difference between the results of Experiments 1 and 2 is in the negative-ambiguous condition. Figures 1 and 2 suggest that the negative-ambiguous trials were apparently learned more readily in Experiment 1 than Experiment 2. Again, if we assume that adding stimulus components increases habit strength, then the difference in habits between the positive-ambiguous and negative-ambiguous conditions is much greater in Experiment 2 than Experiment 1. Thus, it follows that negative-ambiguous performance would be hindered in Experiment 2, but not in Experiment 1. The data from our experiments are of interest for several reasons. First, they show that the pattern of results obtained on ambiguous-cue problems can be altered by manipulating the number of cue components in the stimulus compounds. Therefore, our results closely agree with the predictions derived from the Berth (1974) analysis and can be accounted for within his theoretical framework. Second, these findings have important empirical implications for comparative research in that they demonstrate that human (preschoolers, first graders, retardates) and nonhuman (monkeys, pigeons) subjects perform similarly on ambiguous-cue problems. Finally, it is important to note that this investigation is the first systematic attempt to control for the number of cue components rather than the area of the components possessed by each stimulus (see, e.g., Boyer & Polidora, 1972; Fletcher & Bordow, 1965). Even though this procedural difference has produced no discernible difference in the pattern of results, it could be that overall responding may have been affected. In this regard, it is possible that employing discriminants with

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a precise number of nonspatial cue components has provided accurate test of performance on the ambiguous-cue task.

a more

REFERENCES Berth,

D. B. A theoretical analysis of a PAN ambiguous-cue problem. Learning and 1974, 5, 135-148. Boyer, W. N., Bullock, M., & Viney, W. Effect of stimulus variation upon reversal shift performance of kindergarten children. Psychonomic Science, 1971, 23, 166-167. Boyer, W. N., & Polidora, V. J. An analysis of the solution of PAN ambiguous-cue problems by rhesus monkeys. Learning and Motivation, 1972, 3, 325-333. Boyer, W. N., Polidora, V. J., Fletcher, H. J., & Woodruff, W. Monkeys’ performance on ambiguous-cue problems. Perceptual and Motor Skills, 1966, 22, 883-888. Fletcher, H. J., & Bordow, A. M. Monkeys’ solution of an ambiguous-cue problem. Perceptual and Motor Skills, 1965, 21, 115-l 19. Fletcher, M. J., & Garske, J. P. Response competition in monkeys’ solution of PAN ambiguous-cue problems. Learning and Motivation, 1972, 3, 334-340. Fletcher, H. J., Grogg, T. M., & Garske, J. P. Ambiguous-cue problem performance of children, retardates, and monkeys. Journal of Comparative and Physiological Psychology, 1968, 66, 477-482. Hall, G. An investigation of ambiguous-cue learning in pigeons. Animal Learning & BeMotivation,

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1980, S(2),

282-286.

Leary, R. W. The learning of ambiguous-cue problems by monkeys. American Journal of Psychology, 1958, 71, 718-724. Richards, R. W. Performance of the pigeon on the ambiguous-cue problem. The Bulletin of the Psychonomic

Society.

1973, 1, 445-446.

Thompson, R. Approach versus avoidance in an ambiguous-cue discrimination problem in chimpanzees. Journal of Comparative and Physiological Psychology, 1954, 47, 133-135. Zeaman, D., & House, B. J. Approach and avoidance in the discrimination learning of retardates. Child Development, 1962, 33, 355-372. RECEIVED

March 4, 1980;

REVISED:

March 30, 1981.