Expectancies of reinforcer location and quality as cues for a conditional discrimination in pigeons.

Experiment 1 demonstrated that reliably correlating different reinforcer locations (top vs. bottom) with sample stimuli markedly enhanced the performance of White Carneaux pigeons in a spatial conditional discrimination. This differential outcome effect was more evident at longer retention intervals. In Experiment 2, pigeons were given the opportunity to learn about two redundant reinforcer features--location (top vs. bottom) and quality (grain vs. chow). Which reinforcer feature exerted control over choosing depended on task structure. In the congruent task, where pecks to the top key operated the top feeder and pecks to the bottom key operated the bottom feeder, reinforcer location exerted predominant control. In the incongruent task, where pecks to the top key operated the bottom feeder and vice versa, reinforcer quality exerted exclusive control. These results have implications for the nature of reinforcer representations in instrumental learning.