Retention following appetitive discrimination training: The Kamin effect

Two experiments were performed to investigate retention of a discriminative response under conditions of appetitive motivation. In Experiment 1, four groups of rats received 20 training trials in a two-choice position discrimination procedure. Following training, the subjects received 16 test trials .05, I, or 24 h later on a reversal of the original discrimination problem. The results revealed that retention of the original discriminative training was a U-shaped function of time following training (Le., a Kamin effect was observed), in terms of both associative (percent errors) and performance (response latencies) measures. The data from the second experiment ruled out certain nonassociative explanations for the results of Experiment 1. Thus, the results of these experiments extend the observation of nonmonotonic retention functions to appetitive discrimination learning and provide further support for the hypothesis that an associative mechanism is responsible for such functions.