Predictive accuracy and not reduction in uncertainty influences responding during serial autoshaping

Two experiments with pigeons employed a serial autoshaping design in which food was presented on every trial, and the initial element was of variable duration. When the first element was followed randomly by one stimulus of fixed short duration and another stimulus of fixed long duration, then it elicited a relatively high rate of responding. But when the second elements were of equal mean durations, whether fixed or variable, then responding during the first element was relatively slow. Two explanations for these findings were considered. One stipulates that the rate of responding during a stimulus is related to its predictive accuracy, the other stipulates that responding is influenced by the reduction in uncertainty that follows the offset of a stimulus. It is argued that the evidence favours the first of these alternatives.