An analysis of previous studies of overtraining and reversal learning in rats suggests that overtraining has only facilitated reversal when the discrimination has been a relatively difficult one and the reward used has been relatively large. The results of 3 experiments support this conclusion. In Exp. I with 32 male hooded rats, overtraining had no significant effect on the reversal of an easy position problem, whether a small or a large reward was used; while in Exp. II, using the same procedures and large reward with l6 male hooded rats, overtraining facilitated reversal of a visual problem. In Exp. III with 64 male hooded rats, Ss were trained on an easy or on a hard visual problem with either a small or large reward; only Ss trained on the hard problem with the large reward reversed faster after overtraining. A 2-stage attentional model explains these results better than either frustration theory or a combination of attention and frustration theories. (49 ref.) (PsycINFO Database Record (c) 2006 APA, all rights reserved)