What do you think of this fact?
How fast do you forget things? Hermann Ebbinghaus wanted a number, not a hunch. So in the 1880s, the German psychologist turned himself into his own lab rat.
Learning nonsense on purpose
Ebbinghaus needed material that meant nothing to him, so that no item had a head start. According to Britannica, he invented 2,300 three-letter nonsense syllables for this. Combinations like that have no meaning, so every one of them starts from zero.
He was his own and only test subject. He learned rows of syllables until he could recite them without mistakes, waited a set amount of time and then learned them again. The trick: he measured how much time he saved the second time around. The bigger the savings, the more had stuck. According to an analysis in PLOS ONE, his experiments took about seven months, often with up to three sessions a day.
In 1885 he published the results in his book “Über das Gedächtnis” (On Memory). The most famous of them is the forgetting curve, which describes how forgetting relates to the time that has passed.
The rerun, 130 years later
Psychology has a reputation for results that crumble as soon as someone checks them. So Jaap Murre and Joeri Dros of the University of Amsterdam did exactly that. Dros, the second author, became the test subject himself. He spent about 70 hours learning and relearning lists of nonsense syllables, with gaps ranging from 20 minutes to 31 days.
The result, published in PLOS ONE in 2015: his forgetting curve closely resembled Ebbinghaus’s. The authors write that “the Ebbinghaus forgetting curve has indeed been replicated.” There was one small surprise: the curve isn’t completely smooth and probably jumps up at the 24-hour mark. Whether sleep is behind that, they say, still needs to be tested.
Bonus fact: In the replication, the first two and the last three syllables of a row were the easiest to learn, and most of the forgetting happened in the middle.
One man, a pile of nonsense and a lot of patience mapped out how your memory loses things.