Spaced Repetition

Spaced repetition schedules reviews of a fact at increasing intervals, ideally just before you’d forget it. Each successful recall stretches the next interval, so you spend the fewest reviews for the most retention.

The intuition comes from the forgetting curve: memory decays roughly exponentially, and a well-timed review resets the decay from a higher baseline.

Testing yourself is the review: recall under retrieval pressure is the practice that spacing schedules.

Recall is the practice; spacing is the schedule.

See also: active-recall (not written yet).