Long-Term Memory, Sleep, and the Spacing Effect

Patti-Me_sm_1Matthew_Bell_2Dr. Matt Bell and Dr. Patti Simone are Professors at the Department of Psychology at Santa Clara University. They are also collaborators in the Memory Lab in the Psychology Department at Santa Clara University. Drs. Bell and Simone received their PhDs from University of California San Diego, Dr. Bell with a focus on learning and Dr. Simone with a focus on memory. Their recent paper, titled “Long-term memory, sleep, and the spacing effect” was published in the journal Memory.

Background of the study

We knew from other studies that waiting 24-hrs before restudying resulted in better long-term memory. We wanted to know if the delay alone was important or if sleep during the delay was critical, so we reduced the delay to 12-hrs and had the restudy session either in the same day or the next day.  We then tested their long-term retention 10 days later.

Primary findings

For best retention of information, you should study once, and restudy again the next day.

We found that memory was best when the 12-hr delay included a night’s sleep, suggesting that the sleep episode contributes to the memorial benefit of the temporal separation of study sessions in spacing paradigms. Additionally, the differences in performance (possibly a function of retrieval difficulty) during the first presentation during the restudy phase between the 12 hours same day and 12 hours overnight participants did not result in superior long-term memory. Thus a combination of sleep and contextual variability factors from the passage of time appear to contribute to multi-day spacing effect benefits.

This spacing benefit has been known to researchers for a very long time. It is surprising how rarely it is used by students, educators and textbook writers.

Overall percent correct (9SEM) for each delay shown for the long-term memory test.
Overall percent correct (9SEM) for each delay shown for the long-term memory test.

Next steps

We presented these findings at scientific conferences and published the study in the journal Memory. Our next studies are looking into other factors besides sleep (such as distraction vs. no distraction) to see what else about the delay between study sessions is beneficial to memory retention.

About the department

Santa Clara University is a private, Jesuit institution consistently rated as one of the top undergraduate institutions in the west. Both the school and the Psychology Department have a strong emphasis on research for both faculty and students, and we strive to maintain ourselves as one of the top teaching undergraduate universities. The Psychology Department is an undergraduate department. Our faculty-run labs staffed exclusively by undergraduates and we publish regularly, in high quality journals. As a result, our undergraduates have a number of opportunities to experience aspects of research, including those usually reserved for graduate students. At the same time, they emerge with all the benefits of a liberal arts education, including a breadth of knowledge and an ability to think critically.

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