Simultaneous Discrimination Learning Research Articles

The effect of prenatal exposure to diazepam on aspects of postnatal development and behavior in rats.

In the present study the effects of chronic treatment of pregnant rats with diazepam on the physical and behavioral development of their offspring were investigated. Rats that were diazepam-exposed prenatally were compared to age-matched controls in terms of the following: number of littermates; birth weight and weight gain until weaning: motor development and coordination; simple motor learning; open field activity; performance on learning tasks of varying complexity; retention of these tasks. Nulliparous Wistar rats were injected s.c. for 16 days of their pregnancy was either 2.5, 5, of 10 mg/kg diazepam or an equal volume of vehicle. Prenatal diazepam treatment did not alter litter size, birth weight, or the righting reflex, but seemed to retard early motor development transiently. Diazepam pups showed longer latencies and less rearing in the open field. There were no differences between animals exposed to drug and vehicle in simple motor learning or in acquiring a simple successive discrimination task. However, there were significant dose-dependent differences on a complex six-choice simultaneous discrimination learning task, the diazepam-exposed rats making more errors and taking more time to reach the goal. A significant difference was seen again between diazepam- and vehicle-exposed rats on the retention test 10 days later. The results indicate that diazepam administered to pregnant rats has long-range effects on the behavior of the offspring, some becoming manifest even in maturity.

Distribution of trials and intertrial retention in delayed matching to sample with pigeons.

On the basis of the notion that the events of a delayed matching to sample (DMTS) trial would be forgotten over a long intertrial interval (ITI), it was predicted that a 20-sec ITI would lead to better performance than a 1-sec ITI with a random order of DMTS trials but that a 1-sec ITI would be superior to a 20-sec ITI with a homogeneous order of DMTS trials. Contrary to this prediction, it was found in Experiments 1 and 2 that a 20-sec ITI led to a higher accuracy than a 1-sec ITI with both random and homogeneous orders. In Experiment 3, daily reversal learning was used to show that varying the ITI was directly opposite effects on DMTS with homogeneous orders of trials and on simultaneous discrimination learning; a 1-sec ITI facilitated discrimination learning and hindered DMTS, relative to a 20-sec ITI. Analyses of two-trial sequences within the first three experiments indicated that memories of Trial n - 1 influenced performance on Trial n; pigeons' choice on Trial n reflected a preference for the pattern presented on or for the position of the key most recently pecked on Trial n - 1 regardless of the outcome (reinforced or nonreinforced) of Trial n - 1. In Experiment 4, performance on homogeneous DMTS trials embedded within random DMTS trials, using stimuli from another dimension, was studied. Performance on embedded trials was equally good with massed and spaced distribution of trials and was superior to performance on control trials. It is suggested that the carry-over of memory of preceding trials provides information necessary for successful performance in discrimination learning but acts to interfere with processing of the sample stimulus in DMTS.

The Effects of Introtacts on Hypothesis Testing in Kindergarten and First-Grade Children

Kindergarten and first-grade children were trained against their initial dimensional preference in a 2-dimensional simultaneous discrimination learning task. One third of the children received pretraining in using a sequential hypothesis-testing strategy, one third received pretraining in which they experienced solutions to tasks of the same type, and one third received no pretraining. Half of the children received introtact probes prior to each trial in the criterion task. Introtact probes had no effect on the performance of kindergarten children but facilitated the performance of first-grade children who received pretraining. Performance was generally better in the pretraining conditions than in the control condition and was generally better for first graders than for kindergarten children. Indices of the use of the sequential hypothesis-testing strategy were obtained from the responses to introtact probes. 75% of the first graders who received pretraining in hypothesis testing showed high proficiency in using the strategy, whereas only 38% of the kindergarten children did so. A strong tendency to become fixated on the irrelevant dimension was evident at both age levels.

La discrimination visuelle de formes complexes chez le merle, Turdus merula (L.)

Four blackbirds were trained to make a simultaneous discrimination learning of two complex shapes. All subjects readily mastered the discrimination task. They were then tested for generalization with 20 other paired shapes. In transfer tests, visual recognition remained invariant despite alterations of size, presentations of right, left, upper or lower halves of figures, local distortions, segmentation and camouflages. On the other hand, there was no longer any visual recognition with brightness inversion, rotation or dotted outlines of figures. Our results show that blackbirds perceive and memorise a topographic description of two complex shapes, provided that their orientation is not modified.

The relative importance of responses to S+ and S- in simultaneous discrimination learning.

Earlier research indicated that errors were more important in discrimination learning than correct responses (the Moss-Harlow effect). This conclusion was based on a variety of experimental designs each of which had basic methodological problems, usually involving novelty or order effects. A circular apparatus which allowed the simultaneous presentation of several different stimuli was used to study discrimination learning with S + and S − differentially weighted. It was found that variability in S − was more detrimental to discrimination learning than variability in S + although this finding depended on the presence of a constant stimulus. The results were interpreted as supporting the proposition that in discrimination learning rats learn more to avoid S− than to approach S+.

The Effect of Change in Stimuli on the Transfer of Dimensional Pretraining to the Discrimination Learning of Kindergarten Children

Kindergarten children were given verbal pretaining prior to a simultaneous discrimination learning task under 1 or 2 stimulus conditions. For half the children, the stimuli were changed from the pretaining task to the criterion task; for the other half, the stimuli were identical in the 2 tasks. During pretaining, the children learned to label the values of the dimension that would be either relevant, constant, or irrelevant in discrimination learning. When the stimuli were identical in 2 tasks, pretaining produced significant facilitation and interference effects in discrimination performance. The pretaining effects in the changed-stimulus condition were greatly attenuated and nonsignificant. The relation of these results to earlier findings and to studies of dimensional attention in general is discussed.

Effect of Frequency and Probability of Reward on Choice

In studies of probability and simultaneous discrimination learning choice is typically to the alternative with higher probability of reinforcement. However, in these situations probability of reinforcement is confounded with frequency of reinforcement, since the alternative with higher probability of reinforcement given a response also typically receives a greater absolute number of reinforcements in each session. In the present study pigeons were given separate stimulus training on two keys, with only one key presented on each trial, and numbers of trials and probabilities of reinforcement on each key manipulated to examine separately the effects of frequency of reinforcement and probability of reinforcement in different groups. Choice was examined on choice trials with both keys presented. When frequency and probability of reinforcement were manipulated independently, each of these variables affected choice.

Spatial separation and dimensionality of stimuli in children's discrimination learning.

Research has shown that increasing the distance between stimuli interferes with 2choice simultaneous discrimination learning in kindergartners (2, 3 ) . This effect has been demonstrated both for easv and difficult discriminations. where difficultv is m a n i ~ u lated by varying stimulus similarity ( 3 ) . Another variable influencing task difficulty is stimulus dimensionality. Studies of 3to 5-yr.-old children usually have found that 3dimensional (3-D) stimuli are discriminated more easily than two-dimensional (2-D) stimuli; see review ( 1 ) . The present study explored the effects of spatial separation and dimensionality of stimuli on 2-choice size-discrimination learning of 4-yr.-olds. Six girls and six boys each were assigned to one of four conditions: 2-D near, 3-D near, 2-D far or 3-D far. The 2-D and 3-D stimuli, respectively, were two black cardboard squares and two black wooden cubes. The sides of the squares and of the cubes were 5.08 or 6.35 cm. Stimuli were separated by 6.35 cm. in the near condition and by 25.40 cm. in the far condition. They were presented in a modified Wisconsin General Test Apparatus. The subjects were told, I'm going to hide a marble under one of these squares. Your job is to lift the square you think the marble is under. Stimulus position was predetermined by a modified Gellermann order. The large stimulus was correct for half the subjects of each sex in each condition, and the small one was correct for the remaining half. The learning criterion was 10 consecutive correct responses. The subjects' projected responses on the remaining trials (up to number 60) were recorded as correct. Training was terminated after 60 trials if criterion was not reached. A 2 (separation) x 2 (dimensionality) x 2 (sex) analysis of variance based on number of correct responses yielded a significant main effect of separation = 22.41, p < .001). Subjects performed more poorly in the far condition ( M = 42.20) than in the near condition ( M = 55.43). No other significant main effects or interactions were obtained. These results replicate earlier findings (2, 3 ) that increasing the distance between stimuli interferes with young children's learning. The present study found this effect to be equally strong for 2and 3-dimensional stimuli.

Contrast effects in simultaneous discrimination learning

Pigeons were trained on a form discrimination that alternated across trials with an already-learned color discrimination, which was associated with different probabilities of reinforcement for different groups. The rate of acquisition of the form discrimination varied inversely with the rate of reinforcement for the color discrimination, thus demonstrating a “contrast effect” in simultaneous discrimination learning.

Paradoxical preference for more frequently occurring negative stimuli and for less frequently occurring positive stimuli as a function of amount of training in simultaneous discrimination learning

Development of a preference for more frequently occurring negative stimuli was found in a within-subject design. In this experiment, pigeons learned two simultaneous problems with an unequal number of training trials. At various stages in training, for example, the more-trained negative stimulus was paired with the less-trained negative stimulus for a single preference trial. These probe trials pointed to a swing in stimulus function in negative stimuli which also occurred at an earlier stage in positive (reward-correlated) stimuli. The paradoxical preference for less-trained positive over more-trained positive stimuli was found in this study, confirming the earlier reported phenomenon. The paradoxical preference for more-trained negative stimuli was discussed in terms of a frustration analysis. A symmetrical, albeit positive, emotional factor was discussed with regard to the paradoxical findings with positive probe trials.

Information processing of olfactory stimuli by the dog: II. Stimulus control and sampling strategies in simultaneous discrimination learning

When two discrete stimuli are presented concurrently, with reinforcement contingent on a response to one of them (S+) but not to the other (S−), the redundancy of the situation may allow discrimination by the organism on the basis of information provided by either stimulus or both stimuli. In addition, when the two stimuli are in different positions, only one stimulus need be sampled on any trial to determine where to respond. The actual locus of control (S+, S−, or both) and the sampling strategy are not determinable within the standard acquisition paradigm. Answers to these problems were determined by introducing indifferent stimuli and nonstandard stimulus combinations to three dogs, each of which had previously acquired four simple olfactory discriminations. Results showed that each dog adopted an individual but highly consistent pattern of sampling and control.

Differential effects of chlordiazepoxide on simultaneous and successive brightness discrimination learning in rats.

Chlordiazepoxide (CDP) at a dose of 20 mg/kg, i.p. was found to exert a marked disruptive effect on black-white successive discrimination learning in rats, while this effect failed to be obtained on black-gray simultaneous discrimination. Since trials to the learning criterion were found almost equal for saline rats on both successive and simultaneous discrimination tasks, the differential inhibitory effects of CDP could not be accounted for in terms of differences in difficulties of the two tasks. It is suggested that present results might be interpreted in terms of the hypotheses (a) that CDP produces a deficit in the integration of relevant stimulus cues when they were presented across trials or (b) that CDP has a disinhibitory effect in that inhibition of dominant response (positional preference) patterns is weakened by the drug, in a manner similar to effects observed in hippocampectomized animals.

Effects of Preexposure to Discriminative Stimuli on Discrimination Learning in Goldfish

The purposes of the present study were to examine the effects of nonreinforced preexposure to the discriminative stimuli on the discrimination learning in goldfish (Exp. I), and to investigate the relation of length of daily preexposure time to preexposure effects (Exp. II).The experiment consisted of adaptation and pretraining period (5 days), nonreinforced preexposure period (10 days), and simultaneous discrimination learning period. In Exp. I, 16 goldfish were divided into two groups and preexposed for 22 hours a day in preexposure period : one group (N=8) was preexposed to the discriminative stimuli (Fig. 2, A) while the other group (N=8) was preexposed to the irrelevant stimuli to later discrimination (Fig. 2, B). In Exp. II, 32 goldfish were divided into three groups and preexposed to the discriminative stimuli in preexposure period : one group (N=10) was preexposed for 22 hours a day, the second group (N=12) was preexposed for 30 minutes a day, and the third group (N=10) as a control was not preexposed.The main results were as follows : (1) the groups preexposed to the discriminative stimuli were habituated to those stimuli (Table 1, 2); (2) the groups preexposed to the discriminative stimuli were inferior on the discrimination to the groups not preexposed to the discriminative stimuli (Table 1, 2); (3) the group preexposed to the irrelevant stimuli was superior in performance of discrimination to the group preexposed to the discriminative stimuli and to the control group (Table 1, 2); and (4) the longer the daily preexposure time was, the stronger the preexposure effects (habituation to the discriminative stimuli and inferiority on discrimination learning) became (Table 2).

Effects of verbal pretraining and overt verbalization on discrimination learning in preschool children

Three groups of preschool children received relevant verbal pretraining followed by a simultaneous discrimination learning task in which two irrelevant dimensions varied within settings. In Group B, the irrelevant dimensions varied between settings in pretraining, whereas in both Group W and Group WO, the irrelevant dimensions varied within settings during pretraining. The latter groups differed only in that Group WO was required to name the relevant dimensional values overtly during discrimination learning. Discrimination performance in Group W was significantly superior to that in Group B and did not differ from that in Group WO. The results are consistent with either or both of the following assumptions: (1) Irrelevant dimensional responses were extinguished during pretraining in Group W; (2) stimulus novelty increased the occurrence of irrelevant dimensional responses during discrimination learning in Group B.

Sequential Effects in Simultaneous Discrimination Learning

Latency and accuracy effects were studied with pigeons in a simultaneous discrimination-learning procedure which manipulated sequential randomness of stimulus events from trial to trial. Ss were trained to perform 2 color-discrimination problems with equal or unequal frequency of occurrence. It was found that non-random trial sequences had no effect on over-all acquisition as measured by latency and accuracy, but significant effects from remote trials were a function of the randomness of stimulus events. Performance characteristics on remote trials had significant local effects. In random program sequences, the 2 discrimination problems were learned independently of one another.

幼児の観察学習におけるモデルおよび観察者の反応パタンの分析

69 preschool children were asked to observe a model's response patterns leading to the same reinforcement, and were also requested to perform themselves on subsequent test trials in simultaneous discrimination learning of two shapes. It was found, as expected, that the more an observer observed any specific response patterns, the more the patterns that were observed occurred on the test trials, and that there are two types of observational learning modes; a “one step, nonmediational” mode and a “two or more step, mediational” one.

Strength of dimensional preferences as a predictor of nursery-school children's performance on a concept-shift task

The strength of nursery-school children's dimensional preferences for form and color was scaled by a multidimensional technique, revealing a wide range of strength of preference. Unlike earlier studies, many Ss were found to have equivalent preference for both dimensions. All Ss were then given a two-choice simultaneous discrimination learning problem with either form or color relevant to solution followed by an intradimensional (ID) or an extradimensional (ED) shift. In general, the effects of scaled preferences were in the same direction as, but stronger than, the effects of preference reported in previous studies. The performance of the equal-preference Ss on the original learning task was equivalent to that of Ss who strongly preferred the relevant dimension, and equal-preference Ss learned ID and ED shifts equally well, suggesting that equal-preference Ss may be more flexible in their problem-solving than Ss with a preference for a single dimension. It was further suggested that an age-related hierarchy of preferences progresses from color- to form- to equal-preference.

The “feature positive effect” and simultaneous discrimination learning

Two groups of children were trained to discriminate between two displays which could only be differentiated by a single distinctive feature located on one of the displays. Subjects trained with the distinctive feature located on the positive display learned the simultaneous discrimination while feature negative subjects did not. Recording of finger location of the subjects indicated a localization on the distinctive feature by feature positive subjects while feature negative subjects did not localize on the distinctive feature.

Effects of Correction and Non-Correction Training Procedures on ‘Easy’ and ‘Hard’ Discrimination Learning in Children

The effects of correction and non-correction training procedures on 4- and 5-yr -old children's two-choice simultaneous visual discrimination learning were examined when either ‘easy’ or ‘hard’ tasks were presented. Forty children served as Ss. The results indicated that performance on the more difficult problem was facilitated by the use of a correction procedure. On the other hand, there was very little difference between the group trained with the correction procedure and that trained with the non-correction procedure on the ‘easy’ task.

EFFECTS OF NAMING RELEVANT AND IRRELEVANT STIMULI ON THE DISCRIMINATION LEARNING OF CHILDREN

DICKERSON, DONALD J. Effects of Naming Relevant and Irrelevant Stimuli on the Discrimination Learning of Children. CHMLD DEVELOPMENT, 1970, 41, 639-650. This experiment studied the simultaneous discrimination learning of 80 second-grade children under 4 transfer conditions. Prior to discrimination learning, training was given during which different groups of Ss (20 Ss/group) learned distinctive names (a) for the relevant cues of the discrimination problem, (b) for 2 diferent cues along the relevant dimension, (c) for the variable-irrelevant cues of the problem, and (d) for 2 different cues along the variable-irrelevant dimension. In terms of subsequent discrimination performance, the 4 groups were ordered, from best to poorest, a-b-d-c. This ranking is consistent with a chaining theory interpretation of the results. Backward learning curves showed performance differences among the groups to be not in the slopes of the curves but rather in the length of the initial chance portions of the curves. This latter finding suggests that the 4 training conditions had differential effects upon the probability of attending to the relevant dimension at the start of the discrimination problem.