Science

Spaced repetition — what the studies actually show. The evidence list below names the studies that actually constrain atomic cards.

Scores here are relative ranks inside this atlas, not lab grades or official cut scores.

Evidence

• Forgetting curve — Ebbinghaus (1885) plotted savings on relearning nonsense syllables — a steep early drop then a slower tail, the shape every SRS tries to ride.
• Spacing effect — Cepeda, Pashler, Vul, Wixted and Rohrer (2006, 2008) showed that the optimal gap grows with the retention interval you actually care about.
• Expanding retrieval — Landauer and Bjork's expanding-retrieval work supports starting tight and stretching after hits — the opposite of one cram block.
• Leitner boxes — Sebastian Leitner's box method is a manual SRS: correct cards move right, misses return to box one.
• Classroom transfer — Dunlosky's reviews rank practice testing and distributed practice as high-utility techniques — SRS operationalises both.

Mechanisms

• Study-phase retrieval — Each successful recall is a new encoding, not a photocopy — that is why a hidden answer beats rereading.
• Desirable difficulty — Bjork's desirable difficulty says a recall that takes work sticks longer than a fluent reread that felt easy.
• Interval calibration — Too-short gaps waste time; too-long gaps reset the card. Algorithms estimate the gap from your grade history.
• Interference control — Atomic cards reduce the chance that two facts on one card mask which one you actually knew.

Researchers

• Hermann Ebbinghaus — 1885 memory experiments and the forgetting curve remain the origin story every honest SRS page should name.
• Nicholas Cepeda — Cepeda's spacing meta-analyses and gap-by-retention-interval plots are the modern quantitative backbone.
• Piotr Wozniak — SuperMemo and the SM-family algorithms turned spacing into a daily due queue that students actually run.
• Robert Bjork — Desirable difficulty explains why a slightly late card that you still retrieve is more valuable than an easy reread.

Educational atlas — not an official syllabus, medical advice, or leaked item bank. Spaced repetition: Keep the public outline in view and treat this page as method, not a leaked key.

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