Spaced repetition is a review method in which you revisit material at gradually increasing intervals, timed so that each review happens around the point you would otherwise start to forget it.
How it works
Memories fade quickly after you first learn something, a pattern described by the forgetting curve. Each time you successfully review a piece of information, it fades more slowly than before. Spaced repetition takes advantage of this: review soon after learning, then wait a little longer before the next review, then longer again. Each review is a little effortful because some forgetting has happened, and that effort strengthens the memory.
Most spaced repetition systems combine this timing with active recall. You see a question, try to answer it, then rate how well you did. Cards you know well are pushed further into the future; cards you struggle with come back soon. Over time, your daily review is focused on what you are closest to forgetting.
How to use spaced repetition (steps)
- Turn material into questions. Write flashcards that test one idea each, with a clear question and a short answer.
- Use a scheduler. A spaced repetition app, or a paper Leitner system, decides which cards are due each day.
- Review daily. Do your due cards every day, even if only for 15 minutes. Skipping days creates a backlog.
- Answer before you flip. Say or write the answer before checking it. Recognising the answer does not count.
- Rate honestly. If you hesitated or got part of it wrong, mark it as hard or wrong so it comes back sooner.
- Add cards as you learn. Make cards from each lecture or chapter shortly after studying it, so spacing starts early.
Evidence
The idea goes back to Hermann Ebbinghaus, whose 1885 experiments on his own memory described both the forgetting curve and the benefit of spreading out repetitions. Since then, the spacing effect has been replicated in hundreds of studies. Cepeda and colleagues’ 2006 meta-analysis in Psychological Bulletin reviewed this literature and found consistent benefits of distributed over massed practice, and a 2008 study by Cepeda and colleagues showed that the ideal gap between reviews grows with how long you need to remember the material. Dunlosky and colleagues (2013) rated distributed practice as one of two high-utility learning techniques. Software schedulers trace back to work such as Piotr Wozniak’s SuperMemo algorithm in the late 1980s, which inspired the scheduling used in apps like Anki.
Using spaced repetition with Duetoday
Duetoday generates flashcards from your lecture recordings, PDFs, slides and YouTube videos and schedules them with built-in spaced repetition, so each day you see the cards you are most likely to forget. If you already use Anki, you can export any deck to Anki or CSV. Pair your daily reviews with practice tests on the same material for the most complete review.
