Spaced Repetition
Spaced repetition is a learning technique in which items are reviewed at increasing time intervals — with items you know well reviewed less often and items you struggle with reviewed more often — based on the principle that memory is strengthened most efficiently just before it would otherwise be forgotten.
The psychological principle behind spaced repetition is the "spacing effect", first documented by Hermann Ebbinghaus in the 1880s. Ebbinghaus showed that memory decays in a predictable curve — and that reviewing material just as it is about to be forgotten produces the strongest long-term retention with the least effort.
Modern spaced repetition systems (SRS) — most famously Anki — calculate the ideal moment to review each item based on your previous responses. Answer correctly and the next review is scheduled further away; answer incorrectly and the interval resets. The algorithm does the scheduling work so you always study the right thing at the right time.
For language learners, spaced repetition is most commonly used for vocabulary — often with sentence cards showing a word in context rather than isolated translations. Researchers such as Paul Nation and Nation & Waring suggest that vocabulary items need to be encountered and reviewed many times before becoming reliably accessible, and SRS ensures those encounters happen at memory-optimal moments.
Check your understanding
Your score:
FAQ
What is spaced repetition?
A study technique where you review items at increasing intervals — harder items sooner, easier items later — to maximise long-term retention with minimum study time.
What is the spacing effect?
The psychological finding that memory is strengthened most efficiently when material is reviewed just before it would be forgotten, rather than all at once.
What is Anki?
The most popular free spaced repetition software, used widely for language vocabulary learning. It uses an algorithm to schedule flashcard reviews at optimal intervals.
Is spaced repetition the same as comprehensible input?
No — they complement each other. Spaced repetition is deliberate vocabulary memorisation; comprehensible input is acquiring language implicitly through meaning-focused exposure. Both accelerate learning.