Spaced repetition

Why a review is worth more just before you would forget than just after you learned.

The forgetting curve

Something new fades fast: much of it is gone within a day or two, and what is left fades more slowly after that. Each time it is recalled, the curve flattens.

Reviewing at the right moment

A review just before the memory fades does the most good, so the gap before the next one can grow: a day, then a few days, then weeks. The flash cards here schedule themselves this way.