Sometimes called subconscious plagiarism, Cryptomnesia could be all you need to avoid a lawsuit for infringing copyright material!

Or more seriously, it can explain why some times you think of some thing brilliant, only to find out it was already thought up. "I have a great idea for a book! It will have a boy wizard..." Every one tells you about Harry Potter and you're dumbfounded. One of the things your brain isn't good at is correctly remembering where your ideas come from. Cryptomnesia happens when your brain finds a really good idea, but doesn't bother remembering that it wasn't yours to begin with. You think those lyrics you just wrote down will be chart shattering? Oops, your mind just remembered a line from a song you heard when you were twelve.

Occurrences are pretty rare, or hard to prove at least. After all who would believe you weren't intentionally ripping of JK Rowling? Who would believe your mind just forgot where the idea came from and thought it was your own? George Harrison had to pay out close to $600,000 over a song he "borrowed" from another artist. Was it Cryptmnesia? Maybe. Or a more famous case involving Helen Kellar. She wrote a fairy tale that it turned out had been told to her years before. Maybe she was lying, or maybe it was Cryptomnesia.

And that's the hardest part of Cryptomnesia. You can't prove it happened. Only when it happens to you will you know what it is like. And then you'll have to try and persuade others that it was Cryptomnesia that made you waste three years of your life writing an incredible story about a boy wizard...

Interesting stuff. Some of ideas I had I later discovered that people I know had them too.

I don't know if the 100 monkey sindrome is for real or just a hoax, but It's related to "Cryptomnesia".

Good stuff!