The present investigation was concerned with the reduction of inhibition associated with the negative discriminandum in a single stimulus discrimination learning situation. In Phase I 33 female rats were trained on a black-white discrimination problem. In the second phase Ss were divided into three groups which received: (a) 100% reinforcement to both the old positive and negative discriminanda; (b) four trials per day to the old negative, 100% reward; (c) eight trials per day to the old negative, 100% reward. As in previous studies, which employed simultaneous discrimination learning conditions, speed to the old negative remained significantly below speed to the old positive in the second phase. However, unlike the previous results, the difference decreased over trials. No differences were found between the groups that had trials to the old negative cue only, or between these groups and either speed to the old positive or the old negative in the case of the group receiving reward on both cues.
Differential conditioning in the planarian
