Anki Spaced Repetition — Turning Long-Term Memory into a Systematic Process

Reviewed and verified by FeiYueh · Last verified 2026-09-05

The core of spaced repetition isn't "review" — it's scheduling each act of recall for the precise moment you're about to forget. Anki's algorithm calculates the

The core of spaced repetition isn't "review" — it's scheduling each act of recall for the precise moment you're about to forget. Anki's algorithm calculates the next due date for every card, so you review only once memory strength drops to the critical point, instead of reading the same thing ten times over. This mechanism turns "learn it, forget it" from a willpower problem into an engineering problem a scheduling system can solve. The Empirical Basis of the Forgetting Curve and the Spacing Effect Left alone, human memory decays exponentially. In 1885, psychologist Hermann Ebbinghaus ran self-experiments with nonsense syllables and found that only about 58% was retained 20 minutes after learning, falling to roughly 33% after one day. "Memory retention one day after learning is about 33%" (source: Wikipedia — Forgetting curve) . What matters about this curve isn't the decay itself, but that every successful recall flattens its slope. The benefits of spaced practice have been verified by large-scale meta-analysis. In 2006, Cepeda et al. reviewed 254 experiments comprising over 14,000 data points and found that spaced practice improved accuracy by roughly 9 to 15 percentage points over massed practice (cramming). "254 studies and over 14,000 data points show spaced practice outperforms massed practice" (source: Psychological Bulletin / PubMed) . Meaning: the same total study hours, broken up and spread out, produce a different result. The other pillar is the retrieval practice effect (testing effect). In Roediger and Karpicke's 2006 experiment, the repeated-testing group retained 61% after one week, while the repeated-reading group retained only 40%. "Retention after one week: testing group 61% vs. rereading group 40%" (source: Psychological Science) . Anki binds these two effects together: the card forces you to recall actively (retrieval), and the scheduler decides when you recall (spacing). How Anki's Scheduler Decides When a Card Comes Back Anki began incorporatin

Reviewed and verified by FeiYueh · Last verified 2026-09-05. Independently maintained — not AI-generated boilerplate.