You forget most of what you learn within days — unless you interrupt the curve

In 1885, Hermann Ebbinghaus memorised thousands of nonsense syllables and tested himself for years. He found memory decays on a steep curve — but each well-timed review flattens it. That finding underpins every spaced-repetition app you've ever used.

— Hermann Ebbinghaus, Über das Gedächtnis (Memory: A Contribution to Experimental Psychology) — 1885 — public domain
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