Factors Affecting Conditional Discrimination Learning by Pigeons

Animal Learning & Behavior

Curran

Russell

1988

Self Cite

Four experiments were performed to determine the stimulus characteristics that favor the development of conditional stimulus control in the single reversal paradigm with pigeon subjects. In Experiment 1, pigeons were trained on a successive discrimination between tone frequencies ranging from 350 to 3500 Hz in a particular houselight context condition (houselight-on or -off). The subjects then were trained on the reversal of the tone discrimination in the alternative context. Subsequent tone-frequency generalization testing in the two contexts indicated that they had failed to gain conditional control over the pigeons' discriminative performance. Such control was obtained in Experiment 2, in which the two problems were alternated daily for 32 sessions of training. The gradients then peaked at the appropriate S+ value in each context. In Experiment 3, the key colors (blue vs. red) served as contexts while pigeons learned a successive discrimination in which the discriminative cues were houselight-on versus houselight-off conditions. This was followed by a reversal of the discrimination in the alternative key-color context condition. The key colors were effective conditional cues in this situation. In a previous experiment (Thomas, McKelvie, & Mah, 1985), key color had been ineffective as a conditional cue when the discriminative cues were lines superimposed on the colored background. In Experiment 4, key color was effective when the color and lines were presented on a single key as in the earlier experiment, but were sequenced such that the onset ofthe key color preceded and then overlapped the presentation of the lines. We concluded that conditional discriminations are easiest for pigeons when visual cues are used, but the conditional and discriminative cues must be presented in such a way that they do not combine to form a psychological compound.A typical procedure for studying conditional discrimination learning is to use a background stimulus to indicate the significance of the discriminative stimuli. Thus, in a classic experiment, Lashley (1938) trained rats to select an upright rather than an inverted triangle when the stimulus cards had plain backgrounds and to choose the inverted triangle when the backgrounds were striped. Thomas, McKelvie, Ranney, and Moye (1981) developed a variation of this general procedure, called the single reversal paradigm, in which training on one of the two component problems is completed before training on the reversal problem is initiated. In particular, their procedure begins by training pigeons on a successive discrimination, for example, between two key colors, in the presence of a particular environmental context, such as houselight-on (HL). When the discrimination is mastered after several sessions, the pigeons are then trained on the reversal of the discrimination in the alternative context (houselight-off, HL). Later, retention is assessed via a wavelength generalization test in extinction, with the two contexts alternating in blocks of test trials. The result is that t...

Section: Resultsmentioning

confidence: 99%

Factors affecting conditional discrimination learning by pigeons: II. Physical and temporal characteristics of stimuli

Animal Learning & Behavior

Curran

Russell

1988

Self Cite

“…In the original study by Thomas et al (1981, Experiment 2), approximately 2.5 hr of training time was sufficient. In recent experiments using floor tilt and key color cues (see Thomas, Stengel, Sherman, & Woodford, 1987) and houselight and auditory frequency cues (see Thomas, Curran, & Russell, 1988), even extensive single reversal training failed to produce evidence of conditional control. One reason is certainly the extreme salience of both the houselight and key color cues used in these experiments.…”

Section: Resultsmentioning

confidence: 99%

Does Conditional Discrimination Learning by Pigeons Necessarily Involve Hierarchical Relationships?

J Exper Analysis Behavior

Schmidt

1989

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Four experiments demonstrate that when putative conditional and discriminative cues are presented simultaneously in the single reversal procedure, it is not possible to ascribe a uniquely conditional or uniquely discriminative function to either of the cues. In Experiment 1, pigeons were trained to respond to a blue key and not to a red key while the houselight was on; then in a different session they learned the reversal of this discrimination with the houselight off (single reversal). Separate groups were tested for color generalization with houselight conditions alternating in blocks of trials or for houselight intensity generalization with blue and red key colors alternating in blocks of trials. Both test procedures revealed a conditional relationship between houselight and key color conditions. Experiment 2 produced the same result following training in which the key colors were held constant across training sessions while the houselight and no houselight conditions varied within sessions. In Experiment 3, separate groups were trained with the two procedures but were tested with randomly ordered combinations of key colors and houselight intensities. The two groups yielded indistinguishable bidimensional generalization gradients with peaks at both previously reinforced stimulus combinations. In Experiment 4 the subjects were switched from one of these training procedures to the other with no decrement in their discriminative performance. We conclude that for successive discriminations between conditional- and discriminative-stimulus combinations, the notion of a hierarchical relation between conditional and discriminative stimuli must be extended to include a symmetrical relationship or the notion should be abandoned altogether.

“…Experiment 2 demonstrated that the frequent switching between boxes in Phase 1, designed to invalidate any differences between them as potential retrieval cues, had no noticeable effect on the size of the context-specificity effect. Thomas and Goldberg (1985) had previously shown no significant effect of frequent switching between houselight and tone versus no-houselight and white-noise context, but Thomas et al (1990) and Thomas et al (1987) had shown that frequent switches are essential to establish conditional control by some less salient contextual stimuli. This suggests that the box cues, signaling different locations in the world, are extremely salient to pigeons, despite the fact that the actual cues utilized are not apparent to human observers.…”

Section: Methods Subjects and Apparatusmentioning

confidence: 99%

“…It is well established that conditional discrimination training may be facilitated by providing subjects with frequent and repeated alternations of conditional cues (see Thomas, Cook, & Terrones, 1990;Thomas, Stengel, Sherman, & Woodford, 1987), and in the case of cues that are not very salient, such alternations may be essential. Experiment 2 was performed to test the role of frequent switches between chambers in the initial phase of training.…”

Section: Apparatusmentioning

confidence: 99%

Context Specificity of Operant Discriminative Performance in Pigeons: Ii Necessary and Sufficient Conditions

J Exper Analysis Behavior

Empedocles

Morrison

et al. 1993

Self Cite

Six experiments were performed to explore the necessary and sufficient conditions for producing context specificity of discriminative operant performance in pigeons. In Experiment 1, pigeons learned a successive discrimination (red S+/blue S-) in two chambers that had a particular odor present and between which they were frequently switched. The birds subsequently learned the reversal (blue S+/ red S-) in one of these chambers with a different odor present. When switched to the alternative chamber, although the odor and the reinforcement contingency were still appropriate to the reversal, performance appropriate to the original discrimination recurred in subjects for which the houselights were on during training and testing but not for those for which the houselights were off. This indicated the importance of visual contextual cues in producing context specificity. Experiment 2 showed that the frequent switching between boxes in initial training was of no consequence, presumably because the apparatus cues were highly salient to the subjects. Experiment 3 showed significantly less context specificity when odor cues were omitted. Experiment 4 showed that simply using a different reinforced stimulus in each phase of training was ineffective in producing context specificity. Experiment 5 showed that the generalization test procedure used in Experiment 4 was sensitive to context specificity when discrimination-reversal training was used with different odors in the two training phases.Experiment 6 replicated the results of Experiment 4, but then showed that when different odors accompanied the two training phases, context specificity was obtained with the single-stimulus paradigm. Thus in both single-stimulus and discrimination-reversal paradigms, redundant odor cues potentiated learning about apparatus cues.Key words: context specificity, discrimination learning, reversal learning, odor cues, potentiation, contextual stimuli, recency effect, generalization testing, key peck, pigeonsIn a recent paper, we reported an unexpected and unintended instance of conditional stimulus control by the contexts in which pigeons had learned a successive key-color discrimination and its reversal (Thomas & Empedocles, 1991). The experiment was originally intended to investigate odors as potential "retrieval cues" in pigeons' memory (i.e., as implicit conditional stimuli). The birds first learned to peck a red keylight (S +, reinforced) and not a blue one (S-, extinguished) in the presence of either a eucalyptus oil or isoamyl acetate odor. They were repeatedly switched between two chambers with the same odor to habituate any reaction to the switching that would be required for eventual testing for conditional control by the odors. Next, the birds learned the reversal (blue S+/red S-) in the presence of the alternative odor in one of these Part of this paper was presented at the November, 1991, meeting of the Psychonomic Society in San Francisco. Correspondence and requests for reprints should be addressed to David R. Thomas, Departmen...