Configural associations in discrimination learning.

In 4 experiments, Sprague-Dawley rats and homing pigeons received training with an A+ AB0 BC+ discrimination, in which food (+) accompanied trials with A and BC. Food was not presented (0) on trials with the compound AB. Subsequent test trials revealed that responding during C by itself, or the compound ABC, was slower than during either A or BC. Responding during the ABC compound was also found to be slower after training with the A+ AB0 BC+ than an A0 AB+ BC+ discrimination. We argue that these findings demonstrate the importance of configural associations in discrimination learning. Two accounts for the way in which these associations exert their influence are considered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Selective attention in animal discrimination learning.

2 classes of experiment on the role of attention in discrimination learning are reviewed: (a) Investigations of the effect of attention on the amount learned about different cues have been interpreted as disproving noncontinuity theory (according to which animals attend to only 1 cue at a time). The fact that animals learn something about a 2nd cue, however, does not prove that attention has no effect on learning, and more recent evidence shows that it does. (b) If animals do not automatically attend to all cues, part of what they must learn in order to solve a discrimination problem is to attend to the relevant cue. Experiments on the acquired distinctiveness of cues, transfer along a continuum, and reversal learning provide evidence for the importance of such classificatory learning. (155 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contextual control in discrimination reversal learning.

In 3 human predictive learning experiments, the authors examined contextual control of responding in discrimination reversal learning. In Phase 1, a discrimination between 2 stimuli (A+, B-) was trained in Context 1. During Phase 2, participants received discrimination reversal training (A-, B+) in Context 2. Testing occurred in Context 1 and Context 2 (Experiments 1A and 1B) or in Context 1 and Context 3 (Experiment 2). During the test phase, performance in Context 1 and Context 2 reflected the contingencies trained during Phase 1 and Phase 2, respectively. When testing occurred in Context 3, there was no discriminative responding between A and B. In addition, the experiments demonstrated that discriminating stimuli with a consistent reinforcement history were also affected by contextual manipulations. Results indicate that each training context acquires the ability to control performance. Unique-cue and configural approaches account for a major part of the results. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Elemental associability changes in human discrimination learning.

Participants initially completed a discrimination task (D1) involving categorization of patterns with multiple common features, each feature being partly predictive of the correct response. In a subsequent target discrimination task (D2), these features were redistributed across new discriminative stimuli. The relative predictiveness of the features in D1 was either maintained in D2 (i.e., features were equally informative in D1 and D2) or switched (i.e., more informative features in D1 were made less informative in D2, and vice versa). Differential performance on D2 suggested that features most predictive of the correct D1 responses became more highly associable than features that were less predictive in D1. This finding suggests that the associability of individual stimulus elements changes as a consequence of their role in discrimination learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Change in visual memory following discrimination learning.

Studied visual recognition memory for the size of circles for evidence of active memory change in 3 experiments with 34 paid volunteers and 83 undergraduates. In Exp. I the remembered difference in size between 2 circles which had been discriminated on the basis of size increased, while the remembered difference in size between the same 2 circles discriminated on the basis of brightness did not. In Exp. II, the remembered size of the smallest of 4 circles discriminated by size changed from 1 day to 1 wk. Each S in Exp. III inspected either 1 or 2 circles and was asked to remember their size. There was more memory distortion when 2 circles were remembered, but the distortion did not change over time. The evidence suggests that memory will actively change after a visual discrimination task. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Object discrimination learning in aged Japanese monkeys.

The authors investigated the behavioral aging effects of Japanese macaques in 3-object discrimination learning tasks: learning-set (LS) formation, go/no-go discrimination learning, and multiple discrimination reversals. Aged monkeys showed deteriorated performance in these tasks compared with younger controls. Hypothesis analysis of LS showed that aged monkeys had difficulty learning the lose-shift component of the hypothesis win-stay-lose-shift with respect to object. Deficits in go/no-go successive discrimination were clear in no-go trials only in the first 2 pairs of 5 tasks. Performance of aged monkeys was severely disturbed from a chance to criterion level in discrimination reversals. These results are attributed not only to increased tendency for perseveration but also to difficulty in associating the reward and the object in aged monkeys and may be related to the decline in the functions of the ventral frontal cortex. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Temporal specificity in serial feature-positive discrimination learning.

Two experiments examined the temporal specificity of learning in operant serial feature positive discriminations (feature?→?target+/target–). Test performance was better when the target cues were presented at their customary times after the features than when they were presented at earlier or later times. When features trained with one feature–target interval were combined with targets trained with another interval, performance was best when the test interval was the same as the interval associated with the feature, suggesting that the temporal information was coded with the feature cue. Finally, the temporal specificity of the responding controlled by occasion setters was unaffected by feature extinction. Implications for the nature of learning in occasion setting are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A configural analysis for feature-negative discrimination learning.

In 4 experiments, rats were initially trained with an A+ AXo discrimination in which Stimulus A by itself signaled the delivery of food, A+, whereas the simultaneous presentation of A and X was followed by nothing, AXo. In each experiment, X was then paired with food prior to a test phase in which A and X were again presented for a discrimination. The discrimination was of the form A+ AXo in Exps 1 and 2, whereas it was of the form X+ AXo for Exps 3 and 4. In all 4 experiments, the test discrimination was acquired more rapidly than a control discrimination. The results are interpreted in terms of the original A+ AXo discrimination resulting in the growth of an association between a representation of the entire AX compound and the effects of nonreinforcement. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Auditory evoked-response differentiation with discrimination learning in humans.

To examine the possible functional significance of the registration of the salience of stimulus events in the vertex potential, 40 college students were given a discrimination-learning paradigm involving stimuli that were equally informational but of different value. Wave forms were obtained over the entire course of acquistion. Level of discriminative accuracy and extent of evoked-response differentiation were found to be closely related, indicating that differentiation predominantly reflected improvement in the perceptual-cognitive "labeling" of the stimuli. When the identical stimuli served a feedback rather than a cueing role, evoked responses were markedly different, and there was no apparent relationship to accuracy or learning. (26 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Changes in visual recall memory following discrimination learning.

Trained 100 undergraduates to discriminate among 4 visual stimuli on either 1 of the 2 dimensions which differentiated them: area (large or small circles) or dot density (thickly or lightly filled with dots). Recall was tested immediately or after delay of 4 hrs, 1 day, 1 wk, or 2 wks by having each S draw all 4 stimuli at 1 of these intervals. Differences in recall along the dimension which was discriminated were exaggerated relative to differences on the other dimension. The relative exaggeration was large immediately following testing, declined to a minimum after 1 wk, and increased again after 2 wks. Results are consistent with previously reported changes in visual recognition memory, and suggest a 2-process interpretation. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Review of discrimination shift learning in young children.

Reviews discrimination shift learning studies involving normal 3-7 yr olds to determine under what conditions reversal and intradimensional shifts are easier than nonreversal and extradimensional shifts and vice versa. Variability of the irrelevant dimension, dimensional preference, and overtraining appear to be unequivocal determinants of the relative difficulty of the various kinds of shifts, while verbalization, problem format, and perceptual pretraining are more equivocally related to the relative difficulty of discrimination shifts. (21/2 p ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Same-different texture discrimination and concept learning by pigeons.

Investigated the acquisition and transfer of a "same-different" conditional discrimination using multidimensional visual texture stimuli in pigeons. Using a choice task, 4 pigeons were reinforced for discriminating different displays, created from aggregated differences in element color or shape, from uniform displays, in which all elements were identical. Discrimination of these 2 display types was readily acquired by the pigeons when they were required to locate and peck the contrasting target region of the different displays. The pigeons showed high levels of discrimination transfer to novel texture stimuli both during acquisition and in 2 subsequent transfer tests. The results suggest that pigeons may be able to learn a generalized same-different concept when promoted by the use of large numbers of multielement stimuli during training. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Delay versus probability of reinforcement in discrimination learning.

29 male Carneaux pigeons' responses to compound stimuli were measured as a function of changes in reinforcement delay and probability. A 2-key autoshaping procedure was used in which 2-compound stimuli were successively presented. One compound stimulus was simultaneously correlated with immediate reinforcement and a low reinforcement probability, whereas the other compound was simultaneously correlated with various durations of delayed reinforcement and a high reinforcement probability. Results indicate that reinforcement delay and probability had an interactive effect in discrimination learning. Specifically, the control exerted by a high-probability compound decreased as the reinforcement delay correlated with it increased. Within a critical range of delay values, high- and low-probability compounds exerted equal degrees of control; for even longer delays, the low-probability compound exerted greater control. (14 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Further studies of hippocampal representation during odor discrimination learning.

The contribution of hippocampal and nonhippocampal memory processing to simultaneous-cue odor discrimination learning was assessed. In this task rats with hippocampal system damage consequent to fornix lesions (fornix rats) were severely and persistently impaired in discrimination learning, acquisition of learning set, and concurrent discrimination, although they occasionally solved some problems at a normal rate. By using those problems on which fornix rats succeeded, to permit comparisons of performance strategies with normal rats, differences between groups were shown on response latency measures and on probe trials involving the novel pairing of familiar odors. Normal rats had a bimodal distribution of response latencies, and their latency depended on where the S+ was presented. Fornix rats had short response latencies and responded equally quickly wherever the S+ was presented. Furthermore, when the representation of familiar S+ and S– odor pairs was challenged in probe trials, normal rats responded appropriately to the correct stimulus, whereas fornix rats behaved as if presented with a new odor pair. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Color versus form discrimination learning in 1-year-old infants.

A comparison of form and color discrimination learning in 48 Ss showed that none of the color-trained Ss reached criterion, whereas approximately half of the form-trained Ss did reach criterion. Analysis showed that, in contrast to Ss who were given color problems, Ss who were given form problems showed both an initial curiosity about changes in form and an ability to solve form problems. (7 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Role of reinforcement in discrimination learning set in monkeys.

Analyzes the major theoretical explanations of learning-set (LS) formation in monkeys after reviewing empirical research on the role of reinforcement in LS formation. Studies showing that a reward can function to decrease as well as increase the probability of choosing an object cast doubt upon theories based on an automatic strengthening function of reward. Hypothesis or strategy selection theories avoid this problem by assuming hypotheses, rather than responses, are subject to reinforcement principles, but hypothesis theories are at best incomplete in their treatment of retention. A theory which assumes that LS formation results from between-problem stimulus generalization of feedback from expected rewards is consistent both with retention studies and with experiments on the function of reward in LS, suggesting that LS formation need not be considered a complex abstractive process. (94 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Verbalization effects in discrimination learning of pictures and words.

Compared discrimination learning of pairs of pictures (line drawings) and their verbal labels as a function of various verbalization conditions in a study with 128 undergraduates. Ss either (a) verbalized each item of a pair once (condition C1) or twice (condition C2), (b) verbalized the right item 3 times and the wrong item once (condition R), or (c) verbalized the right item once and the wrong item 3 times (condition W). The R and W conditions affected discrimination learning of both pictures and words in a way predictable from frequency theory, but pictures were easier to discriminate than words in conditions C1, R, and W. It is suggested that the results reflect the joint operation of verbal frequency and visual encoding processes in picture discrimination. (French summary) (17 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Form preferences in successive discrimination learning of young chicks.

In 4 experiments the effects of form and orientation pecking preferences of a total of 100 1- and 3-day old Vantress X Arbor Acre chicks on successive discrimination learning were determined using heat reinforcement. Results indicate that (a) the young chick has both circle and vertical orientation pecking preferences that are present during at least the 1st 3 days after hatching; (b) when either of these preferred cues is the nonreinforced cue, the young chick has difficulty in learning not to respond to it but learns quickly not to respond to an unpreferred cue; and (c) these pecking preferences can be modified by heat reinforcement, and the effects of this conditioning is evident in subsequent extinction and retention tests. It is concluded that form and orientation preferences, like brightness and color preferences, are important developmental constraints on conditioning of the young chick. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Delay of reinforcement in instrumental discrimination learning of rats.

Assigned 4 groups of 8 male albino rats each to a 2-choice discrimination task. Ss were reinforced for pressing 1 lever in the presence of 1 auditory stimulus and for pressing an alternative lever in the presence of a 2nd auditory stimulus. Acquisition of the discrimination was retarded when reinforcement was delayed for all or a random half of the correct responses in the presence of each stimulus. However, performance was facilitated when reinforcement was delayed for all of the correct responses in the presence of 1 stimulus but not the other. Results are interpreted in terms of both classical and operant mediational processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Quokkas ( Setonix brachyurus ) demonstrate tactile discrimination learning and serial-reversal learning.

Two male quokkas (Setonix brachyurus: a herbivorous macropod marsupial) were trained to discriminate pairs of stimuli in the laboratory. Quokkas indicated their choice by pulling on 1 of 2 simultaneously presented cords. The quokkas' discrimination abilities were tested on 6 tactile and 6 visual discrimination tasks. Correct responses were rewarded with food. For both quokkas, all tactile tasks were learned to a criterion of 75% correct in up to 4 20-trial sessions. No visual task maintained criterion performance in 4 sessions. One tactile discrimination was reversed 10 times. After the 1st reversal, the error rate declined sharply and fell to a level well below the initial discrimination. (PsycINFO Database Record (c) 2010 APA, all rights reserved)