The midsession reversal task involves a simultaneous discrimination between Stimulus 1 (S1) and Stimulus 2 (S2) in which, for the first half of each session, choice of S1 is reinforced and S2 is not, and for the last half of each session, choice of S2 is reinforced and S1 is not. With this task, even after considerable training, pigeons tend to make anticipatory errors as they approach the reversal and they continue to make perseverative errors following the reversal. In the present research, we tested the hypothesis that reversal accuracy would improve by devaluing choice of S2 relative to S1. In Experiment 1, correct choice of S1 was reinforced 100% of the time, whereas correct choice of S2 was reinforced only 20% of the time. This manipulation reduced anticipatory errors but did not increase perseverative errors. In Experiment 2, choice of S1 required a single peck, whereas choice of S2 was devalued by requiring 10 pecks. A similar result was found. In Experiment 3 we devalued S1 by requiring 10 pecks and found decreased accuracy in the form of increased anticipatory errors. Paradoxically, in Experiments 1 and 2, by encouraging the pigeons to avoid using the feedback from choice of S2, and rely solely on feedback from choice of S1, discrimination reversal errors were reduced. The results have implications for attentional theories of learning and theories of behavior change. They also have implications for the conditions responsible for pigeons’ tendency to time the occurrence of the change in reinforcement contingencies.

The midsession reversal task involves a simultaneous discrimination in which choice of one stimulus (S1) is correct for the first 40 trials and choice of the other stimulus (S2) is correct for the last 40 trials of each 80-trial session. When pigeons are trained on the midsession reversal task, they appear to use the passage of time from the start of the session as a cue to reverse. As the reversal approaches, they begin to make anticipatory errors, choosing S2 early, and following the reversal they make perseverative errors, continuing to choose S1. Recent research suggests that anticipatory errors can be reduced (while not increasing perseverative errors) by reducing the probability of reinforcement for correct S2 choices from 100% to 20%. A similar effect can be found by increasing the response requirement for choice of S2 from one peck to ten pecks. In the present experiments, we asked if a similar effect could be attained by increasing the number of stimuli that, over trials, could serve as S2. Instead, in both experiments, we found that increasing the number of S2 stimuli actually increased the number of anticipatory errors. Several interpretations of this result are provided, including the possibility that attention to the variable S2 stimuli may have interfered with attention to the S1 stimulus.

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When humans procrastinate, they delay completing a required relatively aversive task. In the present experiments with pigeons, we considered the possibility that completing the task close to the deadline results in the formation of a stronger conditioned reinforcer. In Experiment 1, pigeons were given a choice between two chains: (a) a signaled long period, followed by a dark gap, followed by a signaled short conditioned reinforcer, and food and (b) a signaled short period, followed by a dark gap, followed by a signaled long conditioned reinforcer, and food. We found a reliable preference for the delayed gap. In Experiment 2, we let pigeons choose between two chains: (a) walking to a near panel to peck a key, followed by a long walk to peck a key for reinforcement and (b) walking to a far panel to peck a key followed by a short walk to peck a key for reinforcement. When a single peck was required to either key, the pigeons were indifferent. When ten pecks were required to the near key but only one peck to the far key, the pigeons preferred the far key. When ten pecks were required to either key, the pigeons preferred the far key. The results of both experiments suggest that pigeons prefer to defer a relatively aversive event but, in keeping with Fantino's Delay Reduction Theory, this effect may result from the development of a strong conditioner reinforcer that occurs when the event (the gap or required pecking) comes close to reinforcement.

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