Cryptamnesia

Cryptomnesia occurs when a forgotten memory returns without it being recognized as such by the subject, who believes it is something new and original. It is a memory bias whereby a person may falsely recall generating a thought, an idea, a tune, or a joke, not deliberately engaging in plagiarism but rather experiencing a memory as if it were a new inspiration.

The first documented instance of cryptomnesia occurred in 1874 with the medium Stainton Moses.

The word was first used by the psychiatrist Théodore Flournoy, in reference to the case of medium Hélène Smith (Catherine-Élise Müller) to suggest the high incidence in psychism of "latent memories on the part of the medium that come out, sometimes greatly disfigured by a subliminal work of imagination or reasoning, as so often happens in our ordinary dreams."

Carl Gustav Jung treated the subject in his thesis "On the Psychology and Pathology of So-Called Occult Phenomena" (1902) and in an article, "Cryptomnesia" (1905), suggested the phenomenon in Friedrich Nietzsche's Thus Spoke Zarathustra. The idea was studied or mentioned by Géza Dukes, Sándor Ferenczi and Wilhelm Stekel as well as by Sigmund Freud in speaking of the originality of his inventions.

In the first empirical study of cryptomnesia, people in a group took turns generating category examples (e.g., kinds of birds: parrot, canary, etc.). They were later asked to create new exemplars in the same categories that were not previously produced, and also to recall which words they had personally generated. People inadvertently plagiarized about 3–9% of the time either by regenerating another person's thought or falsely recalling someone's thought as their own. Similar effects have been replicated using other tasks such as word search puzzles and in brainstorming sessions.

Research has distinguished between two kinds of cryptomnesia, though they are often studied together. The distinction between these two types of plagiarism is in the underlying memory bias responsible—specifically, is it the thought that is forgotten, or the thinker? The first type of bias is one of familiarity. The plagiarizer regenerates an idea that was presented earlier, but believes the idea to be an original creation. The idea that is reproduced could be another's idea, or one's own from a previous time. B. F. Skinner describes his own experience of self-plagiarism:

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