THE MIDSESSION REVERSAL TASK WITH PIGEONS: EFFECTS OF A BRIEF DELAY BETWEEN CHOICE AND REINFORCEMENT

During a midsession reversal task, the session begins with a simple simultaneous discrimination in which one stimulus (S1) is correct and the alternate stimulus (S2) is incorrect (S1+/S2-). At the halfway point, the discrimination reverses and S2 becomes the correct choice (S2+/S1-). When choosing optimally, a pigeon should choose S1 until the first trial in which it is not reinforced and then shift to S2 (win-stay/lose-shift). With this task pigeons have been shown to respond suboptimally by anticipating the reversal (anticipatory errors) and continuing to choose S1 after the reversal (perseverative errors). This suboptimal behavior may result from a pigeon’s relative impulsivity due to the immediacy of reinforcement following choice. In other choice tasks, there is evidence that the introduction of a short delay between choice and reinforcement may decrease pigeons’ impulsivity. In the present experiment, a delay was introduced between stimulus selection and reinforcement in the midsession reversal task to assess whether anticipatory and perseverative errors decrease. The results showed a significant difference between the no-delay and delay groups for overall accuracy only during Sessions 11-20, with the no-delay group performing better than the delay group. There was no significant difference in overall accuracy during any other block of ten sessions. These results imply that the insertion of a delay may result in slower learning of this task