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Spaced repetition


Content Reviewers:

Rishi Desai, MD, MPH


Tanner Marshall, MS

Like most students, you’ve probably crammed the night before an exam.

And after it, you probably did OK or maybe you even did well, but did you remember any of what you learned after the exam?

One evidence-based way to better remember what you’ve learned is through Spaced Repetition, or spacing out your learning and practice of new knowledge or skills.

Although this might seem novel, this is hardly a new concept; it was first described in 1885 by a German psychologist named Herman Ebbinghaus. Here’s how it works.

Say you plot your retention, or how much you remember of something, vs. time.

Now you learn that something on day 0.

Without reviewing it, the “forgetting curve” will look like an exponentially decaying curve, which is kind of scary!

If you review (or better yet actively retrieve) the material at increasingly spaced intervals after learning it, then the forgetting curve starts to flatten out and you’ll get a lot better longer-term retention.

Now, the goal here is to review the material at the right time.

It turns out that the best time to revisit information that you are trying to learn is right around the time you would naturally forget it. Since forgetting typically follows this exponential curve, the trick becomes timing your study sessions around it.

Practically, this means having more widely spaced intervals between study times for the material that you are more familiar with, and shorter intervals between study sessions for material that you are less familiar with.

While this strategy would be effective for all fields of study, it is especially important for students in the medical field, who have to retain key knowledge and skills in order to care for their patients.

Kind of frighteningly, one study found that without spaced repetition, after one year medical students forgot up to 33% of their basic science knowledge, and after two years, more than 50%!


Intervals of time between subsequent reviews of learned material to optimize the psychological spacing effect. Spaced repetition is based on the idea of the spacing effect, which states that information is better remembered if it is studied over multiple study sessions, with increasingly long intervals between each session, rather than studying the same information in one intensive session. This technique is used in various forms of learning, including memorization, language learning, and skill acquisition.