A Factor Affecting Stimulus Classes Formation in Concurrent Discriminations in Rats

Abstract

Two experiments examined whether or not rats formed stimulus classes on a basis of same response (i.e., shared common response) during overtraining. In Experiment 1, rats were trained on two discriminations in a straight runway, then trained on conditional successive discriminations in a Y maze. Group C, in which rats were required to choose the same goal box when the original positive stimulus or the negative one was presented on the entrance of each goal box, learned shift problems faster than Group IC, in which rats were required to choose the right goal box when one of positive stimuli was presented and to choose the left goal box when the other was presented as well as negative stimuli, after overtraining, but not after criterion training. In Experiment 2, rats were trained on two discriminations in the Y maze, and then they were trained on either whole reversal (Group W) in which two tasks were reversed or partial reversal (Group P) in which one of two tasks was reversed in a straight runway. Group W learned their reversal faster than Group P after overtraining, but not after criterion training. These results indicate that the same response is a factor affecting stimulus classes formation in rats.