For students and parents · All year
Spaced repetition: what it is and why it works
Spaced repetition means reviewing something at growing intervals, each one timed for just before you would otherwise forget it: a day later, then a few days, then a couple of weeks. It works because memories that are brought back just as they fade become more durable, so fewer, well-timed reviews keep more in your head than the same time spent cramming.
Why do we forget, and why does spacing help?
Soon after you learn something you start to lose it, quickly at first and then more slowly, which is what psychologists call the forgetting curve. Each time you successfully recall it the fall afterwards is gentler, so the next review can safely wait longer than the last one did.
Cramming does the reviews too close together, while the memory is still fresh, so the recall takes little effort and adds little. Spacing the same reviews out means each one takes more effort, and that effort is what makes the memory last. A large analysis of spacing experiments by Cepeda and colleagues also found that the best gap depends on how long you need to remember: the further away the test, the wider the gaps should be.
How does a flashcard app decide when to show a card again?
After each review you say how well you remembered the card, and the app uses that to set the next date: a card you found easy waits much longer, and a card you forgot comes back soon and starts climbing again. Older schedulers, such as the SM-2 method Anki has long used, grow each card’s gap by a multiplier; newer ones, such as the FSRS scheduler that Anki now offers, estimate from your own review history how likely you are to remember each card and schedule it for when that chance drops to a level you set, often nine in ten.
The practical result is that the cards you know well cost you very little time, and your daily reviews go mostly to the ones you are about to lose. Asking for a higher level of remembering is possible, but the number of reviews rises steeply as you get close to remembering everything.
Using it for GCSEs and A levels
Flashcards suit facts, definitions, formulas, quotations and vocabulary, and a few minutes a day keeps a large deck in your head over a whole course. Exam questions need the same spacing but a different kind of practice, since the marks go to applying and explaining what you know, and a topic you answered badly should come back sooner than one you answered well.
The habit that matters most is doing the reviews that are due each day rather than saving them up, because a pile of overdue reviews is cramming again. Starting early helps, since spacing needs weeks to work, but even a few weeks before an exam it does more than rereading.
Where to check
- Cepeda and others (2006), Distributed practice in verbal recall tasks
- Dunlosky and others (2013), Improving students’ learning with effective learning techniques
- Anki manual: deck options and FSRS
Checked against these on . The rules change from year to year, so the pages above are the ones to trust if anything here disagrees with them.
Common questions
What is spaced repetition in simple terms?
Reviewing something just before you would forget it, then leaving a longer gap before the next review each time you remember it.
Is spaced repetition better than cramming?
For anything you need to remember for more than a few days, yes. Cramming can get you through a test tomorrow, but the research on spacing finds that spread-out practice is remembered for much longer.
What is FSRS?
The Free Spaced Repetition Scheduler, an open scheduling method that Anki offers as an alternative to its older one. It estimates from your review history how likely you are to remember each card and schedules the next review accordingly.
Does spaced repetition work for maths and science?
Yes, as long as what you repeat is the skill as well as the fact. Formulas and definitions suit flashcards; methods need spaced practice at questions, coming back to each type of problem over weeks.
How many flashcards should I review a day?
However many are due. The scheduler decides that from how well you know each card, so the number grows when you add many new cards at once and falls as they settle.