Cryptomnesia
Also known as: Unconscious plagiarism, Inadvertent plagiarism
Mistaking a buried memory for an original idea of your own.
What it means
Cryptomnesia is a source-monitoring failure in which a previously encountered idea, melody, or phrase resurfaces and is experienced as a novel, self-generated creation. The content is retrieved while its true source — having heard or read it before — is lost, so the rememberer sincerely believes they invented it. It is the mechanism behind many cases of unintentional plagiarism, where authors and musicians reproduce others' work in good faith. Laboratory studies reliably induce it by having people generate items in domains they had recently been exposed to. It illustrates that creativity and memory share machinery, and that the feeling of originality is itself a fallible source attribution.
How it is studied
Cryptomnesia is one of the few memory errors that can be produced on demand. In Brown and Murphy's original procedure, small groups take turns generating category examples, such as sports or musical instruments, under the rule that no one repeats an item; later each person recalls only their own contributions and also generates fresh ones. Plagiarism appears at both stages. The per-item rate is low, a few percent, but because each participant produces many items, a majority reproduce at least one other person's example without realizing it. Marsh and Bower replaced the group with a computer partner in a word-search puzzle and drew out higher rates, which let them vary the delay before recall and the depth of encoding, both of which shift plagiarism predictably.
What makes it more likely
The factors that raise cryptomnesia all point the same way: anything that weakens the tag linking an idea to its origin. Longer delays, shallow encoding, and time pressure during generation each increase it, because they leave the content intact while the source detail decays or is never recorded. One result is counterintuitive: elaborating on or improving someone else's idea makes you more likely to later claim it as your own. Trying to generate genuinely new ideas produces more plagiarism than trying to recall your own, and people most often lift from whoever contributed just before them. Conversely, deliberately attending to where each idea came from, at the moment of generation, reduces the error.
Why it is a source-monitoring failure
The accepted explanation treats originality not as a stored fact but as a judgment the mind makes after the fact. Under the source-monitoring framework, we decide where a memory came from by weighing its qualities: how vivid it is, how fluently it arrives, what contextual detail comes with it. An idea that returns easily and carries no sense of having been read or heard elsewhere is attributed to the most available candidate source, which is oneself. Cryptomnesia is what happens when that inference misfires, and this account fits the data: manipulations that strip away contextual cues or add cognitive load reliably increase misattribution. Reviews of two decades of work converge on this mechanism rather than on any special hidden-memory faculty.
Real cases and the limits of the lab
Outside the laboratory the best-known examples are musical: George Harrison was found by a US court to have unintentionally reproduced an earlier hit's melody, the judgment resting on copying done, in the court's word, "subconsciously." Comparable disputes recur in fiction, branding, and scientific rediscovery. Two cautions apply. The lab paradigms use trivial, interchangeable items, category words and puzzle answers, so they show the mechanism exists without proving that a whole melody or argument is taken the same way. And in any real dispute cryptomnesia is nearly impossible to separate from deliberate copying after the fact; sincere belief in one's own innocence is exactly what the effect predicts, which makes the defense easy to assert and hard to verify.
Examples
A songwriter pens a 'new' melody that turns out to closely echo a tune they heard years earlier.
In a brainstorm someone floats an idea with real enthusiasm, unaware it was a colleague's suggestion from a meeting three weeks earlier — the content returned, the source did not.
A student writes a phrase that feels entirely their own, and the plagiarism checker matches it to a paper on the reading list they skimmed months ago and forgot.
A designer presents a logo she is certain is original; a colleague later recognizes it as a near-copy of a competitor's mark she had reviewed in a slide deck months earlier and forgotten.
A novelist drafts what she is sure is an original plot twist, not realizing it reproduces one from a paperback she read as a teenager and has long since forgotten.
First described in Term: Théodore Flournoy (1900); experiments: Brown & Murphy (1989).
Key references
- Gingerich, A. C., & Sullivan, M. C. (2013). Claiming hidden memories as one's own: A review of inadvertent plagiarism. Journal of Cognitive Psychology, 25(8), 903-916. doi.org/10.1080/20445911.2013.841674
- Stark, L.-J., & Perfect, T. J. (2008). The effects of repeated idea elaboration on unconscious plagiarism. Memory & Cognition, 36(1), 65-73. doi.org/10.3758/MC.36.1.65
- Marsh, R. L., Landau, J. D., & Hicks, J. L. (1997). Contributions of inadequate source monitoring to unconscious plagiarism during idea generation. Journal of Experimental Psychology: Learning, Memory, and Cognition, 23(4), 886-897. doi.org/10.1037/0278-7393.23.4.886
- Marsh, R. L., & Bower, G. H. (1993). Eliciting cryptomnesia: Unconscious plagiarism in a puzzle task. Journal of Experimental Psychology: Learning, Memory, and Cognition, 19(3), 673-688. doi.org/10.1037/0278-7393.19.3.673
- Brown, A. S., & Murphy, D. R. (1989). Cryptomnesia: Delineating inadvertent plagiarism. Journal of Experimental Psychology: Learning, Memory, and Cognition, 15(3), 432-442. doi.org/10.1037/0278-7393.15.3.432