Serial discrimination reversal learning in the pigeon: Potentiation of "pattern" by a conditional cue.

In 6 experiments 52 domestic pigeons were trained daily on a conditional serial discrimination reversal problem. In the standard training procedure, on odd-numbered days a vertical line was superimposed on a successive wavelength discrimination task. On even-numbered days a horizontal line was superimposed on the reverse wavelength discrimination task. Exps I, II, and III assessed the degree of control acquired by the compound conditional cues (lines plus "days") and by the component elements (lines or "days"). Only Ss trained with lines relevant mastered the reversal task. In testing, when the conditional line stimuli were present, they exerted strong control, and no day effect was noted. However, when tested in the absence of lines, Ss that had had training with the compound conditional cue demonstrated reversal performance controlled by day (i.e., the pattern of alternating reversals had been acquired). Exps IV, V, and VI tested alternate interpretations of the control exerted by the day cue. Results imply that the "potentiation" effect noted is due to separate storage of the wavelength discrimination problems and different retrieval processes elicited by presence vs absence of the line stimuli. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of prenatal exposure to cocaine on conditional discrimination learning in adult rats.

Adult male rats that were gestationally exposed to cocaine and control offspring were trained on an instrumental conditioning task for assessment of the acquisition and reversal of an appetitive conditional discrimination based on olfactory cues. Offspring were derived from Sprague-Dawley dams that had received subcutaneous/ly (sc) injections of 40 mg/kg/3 cc cocaine hydrochloride (C40) daily on Gestational Days 8–20, pair-fed (PF) dams that were injected with saline, nutritional control dams (NC) that received saline injections, and nontreated control dams (LC). There were no differences among the prenatal treatment groups in acquisition of the barpress response or response rate throughout all phases of training. All prenatal treatment groups required approximately the same number of sessions to criterion on the initial odor discrimination. In contrast, adult C40 offspring required more sessions to acquire the reversal of the conditional discrimination than did animals from the other treatment groups (PF, NC, and LC). In addition, even at criterion performance for acquisition of the reversal discrimination, C40 animals exhibited lower accuracy on the 1st 10 responses and made significantly more errors before the 1st reward. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Transfer effects produced by overtraining in the rat.

In each of 2 experiments, 2 groups of 12 male hooded rats were trained on an orientation discrimination in the jumping stand, one group (CT) being trained to criterion and the other being given 150 trials of overtraining (OT). In Exp I the 2 groups did not differ when shifted to a black-white discrimination, but the OT group was superior in learning the reversal of the black-white problem. This result suggests that the beneficial transfer resulting from overtraining does not derive from an increased tendency for the OT Ss to attend to the overtrained dimension. Exp II tested the hypothesis that overtraining produces positive transfer by reducing the Ss' tendency to take up position habits. The OT and CT groups were presented with a choice between oblique stimuli with neither alternative being rewarded. Both groups took up position habits, the OT slightly more rapidly than the CT, and thus the hypothesis was not confirmed. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Olfactory repeated discrimination reversal in rats: Effects of chlordiazepoxide, dizocilpine, and morphine.

Effects of a benzodiazepine (chlordiazepoxide), an N-methyl-D-aspartate receptor antagonist (dizocilpine), and an opiate agonist (morphine) were studied with a procedure designed to assess effects of drugs and other manipulations on nonspatial learning in rats. In each session, rats were exposed to 2 different 2-choice odor-discrimination problems with food reinforcement for correct responses. One problem (performance discrimination) remained the same throughout the study. That is, 1 odor was always correct (S+) and the other was never correct (S-). For the other problem (reversal discrimination), stimuli changed every session. Six different odors were used to program the reversal discrimination; on any given session, S+ was a stimulus that had served as S- the last time it had appeared, S- was a stimulus that had been S+ on its last appearance. Thus, in each session, learning a discrimination reversal could be studied along with the performance of a comparable, but previously learned, discrimination. Chlordiazepoxide interfered with reversal learning at doses that had no effect on the performance discrimination. Morphine and dizocilpine also impaired reversal learning but only at doses that also affected performance of the well-learned performance discrimination. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of drive and incentive magnitude on serial discrimination reversal learning in pigeons and chickens.

32 Seabright bantam chickens and 32 White Carneaux pigeons completed 20 problems of a serial discrimination reversal (SDR) task. 4 levels of drive and 2 levels of incentive were combined in a factorial design. Both species' SDR performance was affected by drive but not incentive. However, drive affected interspecies performance differently. Optimal error reduction occurred for pigeons at 14% weight loss, and for chickens at 22% weight loss. Findings suggest that the effects of procedural variables on SDR behavior can be equated across species and that such equation is necessary before meaningful interspecies comparisons can be made. (32 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)     

A comparison of discrimination and reversal learning for olfactory and visual stimuli in aged rats.

The present study investigated age-related differences in discrimination and reversal learning for olfactory and visual stimuli in 6-month and 24-month-old rats. Rats were trained to discriminate between two pseudo-randomly selected odors or objects. Once each animal reached a criterion on discrimination trials, the reward contingencies were reversed. Young and aged rats acquired the olfactory and visual discrimination tasks at similar rates. However, on reversal trials, aged rats required significantly more trials to reach the learning criterion on both the olfactory and visual reversal tasks than young rats. The deficit in reversal learning was comparable for odors and objects. Furthermore, the results showed that rats acquired the olfactory task more readily than the visual task. The present study represents the first examination of age-related differences in reversal learning using the same paradigm for odors and objects to facilitate cross-modal comparisons. The results may have important implications for the selection of memory paradigms for future research studies on aging. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of proactive inhibition upon the postdiscrimination generalization gradient.

Gave wavelength-discrimination or discrimination-reversal training to 8 groups of 12 naive domestic pigeons in an operant free-responding paradigm. 4 groups were trained, for 30 min. daily, to criterion. 2 of these groups learned the 2nd (reversal) task in a single continuous session (massed practice), while the 2 others continued with 30-min sessions (distributed practice). 4 control groups experienced only the 2nd discrimination, with either massed or distributed practice. All groups were then tested for generalization either immediately or 24 hr. after reaching criterion on the 2nd task. The reversal had no effect on immediate-test gradients. In the delayed test, however, the massed-practice reversal gradient was flatter and showed less area shift than the others, suggesting a proactive inhibition effect. (21 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Eye movements of monkeys during discrimination learning: Role of visual scanning.

In Exps I and II with 7 stumptailed monkeys (Macaca arctoides), Ss were given a series of 2-choice, dot-pattern discrimination reversal problems. Results indicate that the rate of reversal learning was markedly retarded by the experimental condition. The magnitude of the effect was unrelated to the similarity of the uninformative stimulus to the discriminative stimuli. In Exp III, 5 experienced Ss were given a series of discrimination problems without reversals, during half of which the experimental condition was in effect. The results were similar to those of the 1st 2 experiments. In Exp IV (3 experienced Ss), each trial began with uninformative stimuli, which were replaced by the discriminative stimuli when visual scanning occurred. The uninformative stimuli had no clear-cut effect on discrimination learning. Findings indicate that the information provided by above-minimum levels of scanning is not necessary for discrimination learning per se, but it does appear necessary for efficent discrimination learning. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An analysis and evaluation of test and item bias in the prediction context.

Presents a perspective on test and item bias in predicting the performance of individuals in majority and minority groups. It is suggested that a difference between groups in the slope of the regression of the criterion on a test used for prediction represents bias that can frequently be corrected. Given a criterion with adequate measurement properties, the selection of items with essentially equivalent discrimination indices is expected to produce approximately parallel slopes. Accordingly, items having different discrimination indices are themselves biased. Intercept bias, on the other hand, is essentially not under the control of the test constructor. It is argued that the goal of producing a test without intercept bias is an unreasonable one. These problems are illustrated by factor models of intercept bias. It is concluded that relative differences in item-difficulty levels from group to group, given items with adequate discrimination indices, should not be labeled as bias. Such items are not automatic candidates for discard. (13 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Serial reversal learning and the evolution of behavioral flexibility in three species of North American corvids (Gymnorhinus cyanocephalus, Nucifraga columbiana, Aphelocoma californica).

In serial reversal learning, subjects learn to respond differentially to 2 stimuli. When the task is fully acquired, reward contingencies are reversed, requiring the subject to relearn the altered associations. This alternation of acquisition and reversal can be repeated many times, and the ability of a species to adapt to this regimen has been considered as an indication of behavioral flexibility. Serial reversal learning of 2-choice discriminations was contrasted in 3 related species of North American corvids: pinyon jays (Gymnorhinus cyanocephalus), which are highly social; Clark's nutcrackers (Nucifraga columbiana), which are relatively solitary but specialized for spatial memory; and western scrub jays (Aphelocoma californica), which are ecological generalists. Pinyon jays displayed significantly lower error rates than did nutcrackers or scrub jays after reversal of reward contingencies for both spatial and color stimuli. The effect was most apparent in the 1st session following each reversal and did not reflect species differences in the rate of initial discrimination learning. All 3 species improved their performance over successive reversals and showed significant transfer between color and spatial tasks, suggesting a generalized learning strategy. The results are consistent with an evolutionary association between behavioral flexibility and social complexity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of context manipulation on memory and reversal learning in rats with hippocampal lesions.

Conducted 3 experiments with 83 male Long-Evans rats to investigate (a) the memory of hippocampus-damaged Ss, and (b) their ability to modify response strategies in relation to the influence of familiar contextual cues. In Exp I, groups of hippocampal and control Ss learned a simultaneous discrimination habit and were subsequently tested for its retention under variable contextual conditions. All groups recalled the discrimination response to an equally high level when testing conditions were constant throughout, but the hippocampal group showed impaired memory when contextual stimuli at recall testing did not conform to those of original learning. Results of Exp II indicate that the hippocampal impairment was not simply the result of introducing novel stimuli. In Exp III, Ss were administered a reversal learning task with contextual stimuli varied between the 2 tests. The typically observed impairment of hippocampal Ss on this task was reduced by contrasting contextual conditions. Results are seen to support a context-retrieval interpretation of hippocampal function. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial reversal learning in preclinical scrapie-inoculated mice

Acquisition and reversal of a two-choice spatial discrimination were tested in scrapie-inoculated mice. Both acquisition and reversal were normal in mice tested 138 and 103 days prior to the onset of clinical symptoms. At 65 days before onset of clinical symptoms, scrapie-inoculated mice required more trails to criterion in reversal learning, but this effect was not significant in a second experiment (68 days preclinical) and was transient: no effect was seen 33 days before symptoms. However, the course of reversal learning was abnormal in all three late preclinical groups (68, 65 and 33 days before symptoms). Reversal learning in these three groups was characterized by a rapid extinction of the original discrimination, followed by a period, absent in controls, during which performance showed no further improvement. This effect corresponds in time of onset to the appearance of characteristic neuropathological features.     

Neuroendocrine influence on attention and memory.

Examined the effects of melanocyte-stimulating hormone (MSH) on attention and memory under conditions of constant darkness and constant illumination in a study with 60 male Holtzman albino rats. After acquiring a brightness discrimination problem, Ss were given either a reversal or memory task. Ss treated with MSH and those tested in the dark performed the reversal task significantly faster than Ss tested under constant illumination. Although differences in memory were detected between groups, these were not statistically significant. Results are interpreted to suggest that increased MSH levels lead to increased awareness of the environment in the rat and that functionally equivalent behavior among other species may derive from similar neuroendocrine substrates. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An analysis of transfer along a continuum.

10 white carneaux pigeons trained on an easy wavelength discrimination subsequently performed more accurately on a hard wavelength discrimination than did 10 controls trained on the hard problem from the outset. The effect was not a simple consequence of learning an easy problem, for a 3rd group (N=10), initially trained on the hard wavelength discrimination but with a 2nd relevant dimension added, performed no more accurately than controls. Nor was it due to a greater difference in response strengths to the stimuli of the hard problem, since a 4th group (N=10), initially trained on the reversal of the easy problem, eventually performed more accurately than controls. A 2nd experiment with 20 white carneaux pigeons of the same age, further disconfirmed this 2nd analysis, leaving it probable that the basic result is partly a consequence of the strengthening of attention to the relevant dimension. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of neonatal striate lesions and visual experience on form discrimination in the rat.

In two experiments the behaviour of light- and dark-reared infant- and adult-operated striate rats was compared on four discrimination tasks and a variety of related transfer and discrimination reversal tests. Infant-operated rats learned all of the discriminations significantly faster and with less failure than did adult-operated animals. Post-operative rearing condition was not found to play a significant role in this performance difference due to age of operation. Though results of transfer tests for neonatal striate animals were comparable to those of controls, results of initial discrimination (and reversal) revealed significant differences in performance between infant operates and control groups. These results are discussed in terms of specification of the nature of the partial "recovery" of sensory and non-sensory functions by the neonatal operate. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of stimulus similarity in discrimination training upon wavelength generalization in pigeons.

Administered variable-interval training to 30 naive adult pigeons to peck a 550-nm light and then tested them for wavelength generalization. Ss were later assigned to 1 of 3 groups, matched for both relative generalization slope and response rate. One group then received successive discrimination training between the 555-nm stimulus (S+) and a vertical white line on a 555-nm background (S-); another group experienced the same S+ but a vertical white line on a black background as S-. A 3rd group received a comparable amount of single stimulus training with the 555-nm value. On a 2nd wavelength generalization test, the 1st group yielded greater sharpening of generalization than the 2nd group, whereas the 3rd group showed no change from Test 1. Results indicate that the sharpening of generalization gradients by discrimination training was directly related to the similarity of the discrimination training stimuli. (20 ref) (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)     

Hippocampal response patterns during discriminative eyeblink/jaw movement conditioning in the rabbit.

Rabbits were given concurrent training in eyeblink (EB) and jaw movement (JM) conditioning in which 1 tone predicted an airpuff and another tone predicted water. After 10 days of discrimination training, the animals were given 10 days of reversal training. In the discrimination phase, acquisition of the 2 conditioned responses was not significantly different; however JM discrimination errors were much more frequent than were EB errors. In the reversal phase, correct performance on EB trials increased gradually, as was expected, whereas there was immediate behavioral reversal on JM trials. Differences in size and topography of dorsal CA1 multiple-unit responses reflected the ability of the hippocampus to discriminate between stimuli in trained animals, corresponding to the performance of the behavioral discrimination. During JM trials, the rhythmicity of the neural response was further modulated by the type of the prior trial, suggesting the coding of sequential events by the hippocampus. Thus, hippocampal conditioned activity can rapidly change its magnitude and pattern depending on the specific trial type during a concurrent EB/JM discrimination task and its reversal. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reversal learning and resistance to extinction: A review of the rat literature.

Observation of an overtraining reversal effect (ORE) seems to be favored by the use of exteroceptive discriminative stimuli while training on a position response most frequently results in no ORE or a reverse ORE. The review of this literature is preceded by reviews of the literature on resistance to extinction following varying amounts of 100% reinforcement, nondiscriminative training, varying amounts of 100% reinforcement, discrimination training, and reversal learning without overtraining. The data in the last 3 topics provide support for the distinction between exteroceptive stimuli and position response training and suggestions about the variables accounting for the differences in results obtained with the 2 training methods. (2 p. ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)