Any experience the writer has ever suffered is going to influence what he does, and that is not only what he’s read, but the music he’s heard, the pictures he’s seen. ~William Faulkner

The American Psychological Association defines cryptomnesia as “an implicit memory phenomenon in which people mistakenly believe that a current thought or idea is a product of their own creation when, in fact, they have encountered it previously and then forgotten it”.

The word ‘cryptomnesia’ is a portmanteau of ‘crypto’ (from the Greek word ‘kryptos’ meaning ‘hidden’ or ‘secret') and ‘amnesia’.

In 1989, a Southern Methodist University psychologist, Dr. Alan Brown and his student, Dr. Dana Murphy, coined the term ‘cryptomnesia’. They conducted a series of experiments on this phenomenon and found that in 3-9 percent of the cases, the participants would unintentionally accredit other participants' ideas as their own.

Cryptomnesia isn't always related to information from outside sources. There are many incidents where individuals suffer from a memory bias, where they believe that an idea of theirs is novel, when in reality they have encountered that idea long before in their own thoughts.

Studies aiming to determine the causes behind cryptomnesia have found that the more a person focuses on the source of a piece of information, the more likely he is to remember its source. Similarly, less attention paid by a person towards the source, while encountering an idea, is likely to give rise to cryptomnesia.

In ‘Interpretation and Overinterpretation’, novelist Umberto Eco talks about his rediscovery of an antique book among his collection, which was strangely similar to his novel ‘The Name of the Rose’:

I had bought that book in my youth, skimmed through it, realized that it was exceptionally soiled, and put it somewhere and forgot it. But by a sort of internal camera I had photographed those pages, and for decades the image of those poisonous leaves lay in the most remote part of my soul, as in a grave, until the moment it emerged again (I do not know for what reason) and I believed I had invented it.

Plagiarism is an unethical deed and can lead to dire consequences for the plagiarist at times. But when cryptomnesia comes into play, the creator in question is definitely not at fault. However, in spite of cryptomnesia being a real memory phenomenon, the legitimacy of the occurrence of cryptomnesia is doubted at times cause unfortunately lots of plagiarists after being caught, lie about having encountered cryptomnesia and it is difficult to come across confirmed cases of cryptomnesia.