The purpose of the present experiment was to study the extinction effect of partial reward and nonreward followed by continuous reward. Each of 30 male white rats was trained under 3 phase procedure in the straight runway consisting of three sections. The first phase consisted of 30 continuous reward trials for all groups. The second phase for P-group consisted of 30 partial reward trials (50%random reward), that for N-group consisted of 30 nonreward trials, and that for C-group (control group) consisted of 30 continuous reward trials. The third phase for all groups consisted of 30 continuous reward trials. Then, all groups were subjected to 30 extinction trials.
Results from these three groups in extinction were as follows :
1. The performance of P-group was superior to that of N-group, which had a tendency to be superior to C-group.
2. The effect of reward schedule during acquisition upon extinction was most remarkable at the starting speed, and became weaker, as the subject went near the goal box, and the days went on. The performance level of goal speed was higher than that of starting speed.
Through these results, it was suggested that the interaction of reward trial and non-reward trial should be studied further and that the events of goal box in extinction might be different from the events of nonreward trials in acquisition.