The Spacing Effect

by Site Author

Suppose that you’re preparing for some kind of performance. Perhaps you’re studying for an exam, or rehearsing a presentation, or gearing up for a job interview. What if I told you that I could double the effectiveness of your rehearsals? What’s more, I can do that without forcing you to actually spend any more time rehearsing than you are now.

Too good to be true? It’s all based on a concept called “spaced repetition.” The basic research on spaced repetition dates back to the 19th century, and has been consistently replicated by psychologists ever since. In fact, spaced repetition is so effective that psychologists have taken to writing papers asking why it’s not more widely known.

Take, for instance, an early discovery of spaced repetition. William Pyle, a psychologist at the University of Missouri, published a paper in 1913—1913!—on the spacing effect. He described a simple experiment involving a small group of third-grade children studying addition. One group was given ten minutes of practice once a day for two weeks. The other group was given ten minutes of practice twice a day for one week. Both groups were given the same amount of time to practice, but one group had that practice spread out over two weeks rather than one.

The figure below comes from Pyle’s study. The two “learning curves” plot test scores for the two groups of students. The upper curve comes from the group practicing for two weeks rather than one week.

Pyle's Learning Curves

To be clear, both groups were of equal ability at the start of the experiment, and were randomly assigned to these two treatments. The group that had its practices spaced out over two weeks rather than one week ended up learning much more.

This basic pattern has been replicated countless times. Just search the literature for the “spacing effect” or “distributed practice.” It applies to children and to adults, to rote memorization and to deep learning. There have been many studies since this one, and they tend to produce the same kind of learning curves.

I have written about this before. In that post, I focused on the implications of the spacing effect for rehearsing a presentation. It applies, however, to much more than just presentations. Whenever you are preparing for anything, it is worth spacing out that preparation over time. If you really only have a day to prepare, then break up your practice schedule over the course of the day. But if you have longer to prepare, the more you can distribute your preparation across days, the better.