In the cognitive skill literature, between-session delays have been treated either as having a negligible effect on performance or as causing forgetting. In contrast, in the procedural skill literature, overnight between-session delays can result in performance gains. In 5 multi-session data sets, the author demonstrates that neither of these 2 models holds for the case of cognitive skill learning. Instead, the delay between sessions appeared to yield both forgetting and enhanced potential for new learning. Two candidate classes of explanation are considered, and implications for the empirical law of learning are discussed.