The present study examined effects of pre-and post-reinforcer delays on pigeons' choice using concurrent-chains schedules. Subjects were exposed to concurrent-chains schedules in which a single variable-interval 30-s schedule was arranged for the initial link, followed by different fixed-time schedules for pre-and post-reinforcer delays as the terminal links. The pre-and post-reinforcer delays were fixed at 2 s for one alternative and they were manipulated across conditions (2 s, 8 s, 20 s, or 40 s) for the other alternative. Based on the sensitivities estimated from the overall reinforcement density model, it is suggested that pigeons have higher sensitivity to the pre-reinforcer delay relative to the post-reinforcer delay. These results are consistent with those reported in a previous study using rats. Comparisons of choice proportion data from different post-reinforcer delays reveal that pigeons have sensitivity to post-reinforcer delay, although it is not high.

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