Spaced Repetition

The same forgetting curve as the last lesson, turned into a schedule: when to hit review so each fall is slower than the last, instead of starting over from zero.

Before you start. How Memory Works showed you that a memory isn’t a recording you replay, it’s a guess you rebuild each time, and that guess fades on a curve: fast at first, then slow. This lesson takes that curve and answers the practical question it leaves open - if forgetting is coming anyway, when should you fight it?

The idea in 30 seconds

Memory fades fast at first and slowly after that, so review works best right before you would forget, not right after you learned.
The same total study time split across several days beats one long cramming session, because a little forgetting in between is what makes the next review count.
Answering a question from memory strengthens it far more than re-reading the answer does - struggling to recall it is a sign the review is working, not a sign you failed.
The harder a review feels, right up to the point of almost failing, the more it actually strengthens the memory; an easy review teaches almost nothing.
Five boxes of index cards, each checked less often than the last, can run a spaced review schedule with no app: get a card right and it moves to a longer gap, get it wrong and it goes back to daily.

Read the story · Skip to the numbers