See http://en.wikipedia.org/wiki/Cryptomnesia. Cryptomnesia is inadvertent or unconscious plagiarism (Gk. kryptos, “hidden” + mneme, “memory,” hence Jung’s term in Man and His Symbols : “concealed recollection”).
(This blog, like many of mine, is conscious plagiarism: a kind of wiki-mash-up or another entry in my wikipediary.)
= a memory bias, or lapsus memoriae, whereby a person falsely recalls generating a thought, an idea, a song, or a joke, when it was actually generated by someone else (the term was coined by Theodore Flournoy in his occult psychology From India to the Planet Mars [Harper, 1900] and written up by Jung in “Cryptomnesia” in 1905)
There are two common kinds of cryptomnesia, classifiable by the underlying memory bias responsible for them—specifically, is it the thought that is forgotten or the thinker?
- The first type results from familiarity (or “priming”), whereby we regenerate an old idea, someone else’s or our own, but believe it to be new, i.e. because it is an implicit memory (apparently they are stored in different brain regions).
This is occurrence forgetting, a type of generation error. (It is a kind of “sleeper effect,” whereby a highly persuasive message [+ I like this idea . . .], paired with a discounting cue [- . . . but it belongs to someone else or . . . and it happened at a certain time], causes an individual to be more persuaded by the message over time [+ I like this idea—per se]).
- The second type results from an error of authorship whereby someone else’s idea is remembered as our own, i.e. it is a misattributed memory (here we know the idea is old).
This is source forgetting, a type of recognition error.
According to wikipedia, the phenomenon is more prevalent when
- we were under high cognitive load when we first considered the idea
- we are away from the original source of the idea
- someone else produces an idea immediately before we do
- the idea was originally suggested by someone of the same sex
- the idea was not reinforced through use, so there is enough of the memory left to recall it but not its origin.
Daniel L. Schacter describes cryptomnesia as a “mirror image” of a phenomenon such as false recognition, the cause of eyewitness misidentifications. In false recognition, “people misattribute a feeling of familiarity to [“familiarise”] a novel event [cf. paramnesia or déjà-vu], whereas in cryptomnesia, people misattribute novelty to [“defamiliarise”] something that should be familiar” [cf. jamais vu] (The Seven Sins of Memory: How the Mind Forgets and Remembers  108; see “What a Great Idea I Had” 107-11).
To cut to the chase . . .
The difference between unconscious plagiarism and influence (and between it and zeitgeist, for that matter), particularly in the creative arts, is nebulous. The taste of artists develops, in part, mimetically: through emulation, imitation, citation/quotation, elimination, and other forms of borrowing, so we cannot help but be indebted to forebears or “influences.” (Thus, every artwork is an exquisite corpse, in the Surrealist sense: a collaborative, randomised assemblage of words or images.) One myth about influence is that at some point the development of our taste we are miraculously forgiven that debt; it could be argued, rather, that mature taste is open about its indebtedness (in popular music, John Lennon’s return to rock’n’roll in 1975 and Bob Dylan’s to folk in 1992 and blues in the following decade spring to mind)—though this is often seen as evidence of creative exhaustion. In fact, I’d argue that in the formative periods of the development of an artist’s taste (for example, when we analyse and learn by practice from our forebears) we are banking them for the future; to extrapolate, our forebears become indebted to us in a “future anterior” (will have been) sense.
There are also paranormal (or occult) versions of the phenomenon, Jung’s theory of archetypes (“noetic memes” perhaps) being a more worked-through example—not unlike Plato’s theory of anamnesis; the memories “return” under hypnosis, at a séance, in xenography (automatic writing), and other procedures that mobilize the unconsious. See http://www.themystica.org/mystica/articles/c/cryptomnesia.html (caveat lector).
- In the first empirical study of cryptomnesia, people unconsciously plagiarized about 3–9% of the time (A. S. Brown and D. R. Murphy, “Cryptomnesia: Delineating Inadvertent Plagiarism,” Journal of Experimental Psychology: Learning, Memory, and Cognition 15 : 432–42).
- Precedent in United States copyright law is to treat alleged cryptomnesia no differently from deliberate plagiarism (cf. Bright Tunes Music v. Harrisongs Music , where the publisher of “He’s So Fine,” written by Ronald Mack, demonstrated that George Harrison borrowed substantial portions of his song “My Sweet Lord” from theirs; the Court imposed damages despite a claim that the copying was subconscious).