Midsession reversal learning: why do pigeons anticipate and perseverate?

Abstract

Past research has shown that when given a simultaneous visual-discrimination midsession reversal task, pigeons typically anticipate the reversal well before it occurs and perseverate after it occurs. It appears that they use the estimation of time (or trial number) into the session, rather than (or in addition to) the more reliable cue, the outcome from the previous trial (i.e., a win-stay/lose-shift response rule), to determine which stimulus they should choose. In the present research, we investigated several variables that we thought might encourage pigeons to use a more efficient response strategy. In Experiment 1, we used a treadle-stepping response, rather than key pecking, to test the hypothesis that reflexive key pecking may have biased pigeons to estimate the time (or trial number) into the session at which the reversal would occur. In Experiment 2, we attempted to make the point of reversal in the session more salient by inserting irrelevant trials with stimuli different from the original discriminative stimuli, and for a separate group, we added a 5-s time-out penalty following incorrect choices. The use of a treadle-stepping response did not improve reversal performance, and although we found some improvement in reversal performance when the reversal was signaled and when errors resulted in a time-out, we found little evidence for performance that approached the win-stay/lose-shift accuracy shown by rats.

Figure 1

Experiment 1. Percentage choice of S1 as a function of 5-trial block number averaged over pigeons for Sessions 41-50 (solid circles) compared with spatial reversal data (open circles) from Rayburn-Reeves et al. (in press) . The dotted line indicates the point at which the reversal occurred in the session.

Figure 2

Experiment 1. Percentage choice of the first correct stimulus (S1) as a function of trial number for trials 36-45, averaged over subjects, for Sessions 41-50 (closed circles) compared with spatial reversal data (open circles) from Rayburn-Reeves et al. (in press). The dotted line indicates the point at which the reversal occurred in the session.

Figure 3

Experiment 2. Percentage choice of S1 as a function of block number averaged over pigeons in both the control (open circles), time out group (solid circles) and irrelevant trials group (solid circles, dashed line) for Sessions 71-80. The dotted line indicates the point at which the reversal occurred in the session.

Figure 4

Experiment 2. Percentage choice of S1 as a function of trial number for trials 36-45 averaged over pigeons in both the control (open circles), time out group (solid circles) and irrelevant trials group (solid circles, dashed line) for Sessions 71-80. The dotted line indicates the point at which the reversal occurred in the session.