Interaction of memories and expectancies as mediators of choice behavior.

The interaction of food-based memories and food-event outcome expectancies in pigeons was assessed using a simultaneous, delayed-symbolic-matching-to-sample procedure. The components of the compound sample were presented in sequence, and consisted of a food-based event (food or no-food) followed by a color cue (red or green). Choice of a pattern of horizontal lines was "correct" following presentation of the red cue, while choice of a vertical line pattern was "correct" after green. In all but a control condition, the food-based event with which a trial began, or the food-event outcome with which a trial concluded, or both, were also correlated with the correct pattern. Of particular interest was the relative accuracy of two groups for whom both memories and expectancies were correlated with the correct choice-pattern. For one group, the memories and expectancies corresponding to the pre- and postchoice food-related events were similar, whereas for the other they were dissimilar. Outcome expectancies supported a higher level of performance than food-based memories, and subjects with both outcome expectancies and food-based memories chose more accurately than those with memories or expectancies only. In addition, subjects with dissimilar food-based memories and outcome expectancies chose more accurately than those with similar memories and expectancies. The implications of the above findings for the nature of event representation in pigeons are discussed.