Cepeda et al. (2008)

Spacing Effects in Learning

Psychological Science, 19(11), 1095-1102

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Abstract

To achieve enduring retention, people must usually study information on multiple occasions. How does the timing of study events affect retention? Prior research has examined this issue only in a spotty fashion, usually with very short time intervals. In a study aimed at characterizing spacing effects over significant durations, more than 1,350 individuals were taught a set of facts and—after a gap of up to 3.5 months—given a review. A final test was administered at a further delay of up to 1 year. At any given test delay, an increase in the interstudy gap at first increased, and then gradually reduced, final test performance. The optimal gap increased as test delay increased. However, when measured as a proportion of test delay, the optimal gap declined from about 20 to 40% of a 1-week test delay to about 5 to 10% of a 1-year test delay. The interaction of gap and test delay implies that many educational practices are highly inefficient.

Reference

Cepeda, N. J., Vul, E., Rohrer, D., Wixted, J. T., & Pashler, H. (2008). Spacing Effects in Learning. Psychological Science, 19(11), 1095-1102. https://doi.org/10.1111/j.1467-9280.2008.02209.x

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1 mechanism cites this source. Each finding below is quoted as it appears on that mechanism's own page.

Forgetting Memory Processes

Measured in humans

In more than 1,350 people taught facts, reviewed after a gap of up to 3.5 months and tested up to a year later, the best gap was about 20 to 40% of a 1-week test delay but only about 5 to 10% of a 1-year delay