Hermann Ebbinghaus Memorized 2,300 Nonsense Syllables to Show How We Forget

Hermann Ebbinghaus was a 35-year-old German philosopher in 1885 when he published the first scientific study of human memory, Über das Gedächtnis. Psychology at the time was a branch of philosophy. Memory, like emotion, was understood by introspection. Ebbinghaus's idea was to bring it into the lab the way physics had been brought into the lab — by isolating a variable, measuring it precisely, and modeling it mathematically.

The variable was forgetting. To control for the prior associations that adhere to any real word — table sounds like things you've already learned — Ebbinghaus invented the nonsense syllable: a three-letter consonant–vowel–consonant string like ZOF, TUS, or WID that has no semantic foothold. He compiled thousands of them. Then he sat down, alone, in a quiet room, and trained himself on lists of varying lengths until he could recite each one perfectly. He recorded how many trials it took. After a delay — twenty minutes, an hour, a day, six days, a month — he sat down again and trained himself on the same list back to mastery. The savings, expressed as a percentage of the original training time he didn't need to repeat, gave him a measurement of what he'd retained.

The results were the forgetting curve. Memory of newly learned material drops sharply in the first hour, drops more slowly across the first day, and then continues to decay at a much slower rate for weeks. The curve is roughly exponential. Ebbinghaus reported his data with a precision that makes a modern psychologist's eyes water — he was the only subject, but the methodology was clean enough that a 2015 replication produced essentially the same curve 130 years later. The cost was personal: by the end of the protocol he had memorized something on the order of 2,300 nonsense syllables.