Instrumental responses become associated with reinforcers that differ in one feature

Abstract

In three experiments, thirsty rats were trained to make several instrumental responses whose outcomes differed in which of two relatively inconsequential flavor features they contained. In Experiment 1, one of the features was subsequently devalued by pairing it with lithium chloride; in Experiment 2, it was enhanced in value by pairing it with sucrose. In both experiments, differences in the value of the features resulted in parallel differences in the likelihood of the responses during a subsequent extinction test. In Experiment 3, the animals chose between these responses in the presence of discriminative stimuli that had signaled the occurrence of these different features following another response. The stimuli selectively augmented the likelihood of the response with which they shared training by the same-flavored consequence. These results indicate that rats can separately encode features that differ along one dimension, both in the association between an instrumental response and its outcome, and in the association between a discriminative stimulus and that outcome.