Pigeons' use of cues in a repeated five-trial-sequence, single-reversal task

Abstract

We studied behavioral flexibility, or the ability to modify one's behavior in accordance with the changing environment, in pigeons using a reversal-learning paradigm. In two experiments, each session consisted of a series of five-trial sequences involving a simple simultaneous color discrimination in which a reversal could occur during each sequence. The ideal strategy would be to start each sequence with a choice of S1 (the first correct stimulus) until it was no longer correct, and then to switch to S2 (the second correct stimulus), thus utilizing cues provided by local reinforcement (feedback from the preceding trial). In both experiments, subjects showed little evidence of using local reinforcement cues, but instead used the mean probabilities of reinforcement for S1 and S2 on each trial within each sequence. That is, subjects showed remarkably similar behavior, regardless of where (or, in Exp. 2, whether) a reversal occurred during a given sequence. Therefore, subjects appeared to be relatively insensitive to the consequences of responses (local feedback) and were not able to maximize reinforcement. The fact that pigeons did not use the more optimal feedback afforded by recent reinforcement contingencies to maximize their reinforcement has implications for their use of flexible response strategies under reversal-learning conditions.

Figure 1

Experiment 1. Percentage choice of the first correct stimulus (S1) as a function of the trial in the sequence averaged over subjects and for Sessions 41–60, plotted separately for sequences on which the reversal occurred on Trial 2, 3, 4, or 5.

Figure 2

Experiment 1. Percentage choice of the first correct stimulus (S1) as a function of the trial in the sequence pooled over sequence types and averaged over subjects for Sessions 41–60. Squares represent the probability of reinforcement for choice of S1 as a function of trial number, independent of reversal location. Triangles represent the probability of reinforcement for choice of S1 as a function of trial number if subjects were matching choice of S1 to the probability of reinforcement for choice of S1.

Figure 3

Experiment 2. Percentage choice of the first correct stimulus (S1) as a function of trial in the sequence, averaged over subjects and over Sessions 41–60 plotted separately for each sequence type.

Figure 4

Experiment 2. Percentage choice of the first correct stimulus (S1) as a function of trial in the sequence pooled over sequence types. Squares represent the probability of reinforcement for choice of S1 as a function of trial number, independent of reversal location. Triangles represent the probability of reinforcement for choice of S1 as a function of trial number if subjects were matching choice of S1 to the probability of reinforcement for choice of S1.