The Interactive Effects of Sleep and Retrieval on Retention

Engaging in retrieval practice enhances memory relative to restudying (i.e., the testing effect) and a night of sleep after learning enhances memory relative to a day of wake. While both retrieval practice and sleep benefit memory, individually, their interactive effects are more nuanced. Sleep has been shown to moderate the testing effect when no feedback is given during retrieval practice, benefiting only restudied items. However, when feedback was provided during retrieval practice, sleep benefited both retrieval practiced and restudied material. The current study replicated past work in this area using educationally relevant materials (i.e., non-fiction passages) and examined whether memory strength could account for the preferential benefits of sleep for restudied and retrieval practiced material with feedback. In an initial learning session, participants read nine passages and then completed three, six-minute study phases. In the retrieval study phases, participants answered multiple choice items with (retrieval practice plus feedback phase) or without (retrieval practice phase) corrective feedback, while in the re-read study phase, participants read-read passages. After a 12-hour delay spanning nocturnal sleep or daytime wakefulness, participants completed a final memory test. Retrieval practice led to greater recall on a final memory test than restudying, and this difference was largest when feedback was provided. There was no measurable benefit of sleep for final test performance in any of the study conditions; however, sleep resulted in less forgetting between retrieval practice testing and the final memory test when feedback was provided during retrieval practice testing. This seeming conflict in results can be explained by the unexpected time-of-day effects present in our study. These time-of-day effects were driven by the Prolific participants in our sample, and highlight the importance of including short-delay control groups and non-college student participants in studies of sleep and memory.