Spaced repetition
the spacing effect · distributed practice
Spaced repetition spreads the same material over widening gaps, so each review lands before it is gone.
What it is
Studying something three times in one evening and studying it three times across three weeks leave very different amounts behind. Spaced repetition is the second one, done on purpose.
The idea was never the hard part; the scheduling is. A learner has dozens or hundreds of items, each sitting at its own point on its own forgetting curve, and nobody can track that many clocks by hand.
Why the gaps help
Retrieving something that has begun to fade takes more effort, and that effort is the active ingredient: a recall that nearly failed strengthens the memory more than one that came easily.
Spacing also moves each review into a new context — another day, another room, other subjects in between — so the memory gets attached to more cues and stops depending on the desk you first met it at.
How long to wait
There is no universal number. A workable start: the same evening, then day three, then a week, then a fortnight. When a recall clearly fails, pull the next gap back shorter rather than pushing harder.
The more common failure is the opposite one: gaps so short that you still remember the answer perfectly, which is not spacing at all. Judge it by the strain you feel at review time, not by days ticked off.
Common mistakes
- Turning it into "look at every card every day". That is re-reading, and re-reading feels productive precisely because it asks so little.
- Adding new items endlessly while nothing old ever disappears, until the pile is too frightening to open.
- Reading a broken streak as a verdict. Falling behind for three days is the normal shape of this; shorten the gaps and resume instead of abandoning the set.
Things you can try today
- Write the date of your last successful recall on each card and let anything older than three days come to the front.
- Put the items you keep missing into a separate small pile and meet them tomorrow, apart from the main queue.
- Cap the daily workload before you grow the deck. A queue you finish beats a bigger one you avoid.