Forgetting Curve

The forgetting curve, first documented by the German psychologist Hermann Ebbinghaus, describes how the strength of a memory declines over time when no effort is made to review or retain it. Between 1880 and 1885 Ebbinghaus tested himself repeatedly on lists of invented, meaningless syllables such as WID and ZOF, spaced across varying intervals, and published the resulting curve along with a mathematical equation approximating it in his 1885 book Uber das Gedachtnis, translated into English as Memory: A Contribution to Experimental Psychology; a 2015 replication using a single subject produced results similar to his original data. The curve he plotted shows that people tend to lose roughly half of newly learned information within days or weeks unless they consciously review it, a pattern later cited as an illustration of transience, one of the seven fundamental ways human memory fails described in the psychologist Daniel Schacter's book The Seven Sins of Memory; Ebbinghaus's use of artificial, meaning-free syllables and repeated self-testing became a standard method in later experimental memory research.