Generally speaking, we’re likelier to remember a message’s content than its source. This isn’t a bad thing: our capacity for encoding information is finite, and somewhere along the line (be it in evolutionary or developmental increments) we’ve learned to prioritize. It’s more important for me to know that my rec league soccer game is at 1:30 on field #6 than to know that it was Doug, and not his wife, who told me this. Of course, if I had reason to mistrust Doug—if I felt he might (not unreasonably) want me as far away from the field as possible around game time—I might have encoded the event differently. If Doug had been mauled by a badger while he passed along the message, I almost certainly would have encoded the event differently. But barring such dramatics, our memory for the specific context in which knowledge has been acquired is spotty.

This is what makes plagiarism so tough. To be fair, there’s plagiarism and then there’s plagiarism (the first can be said normally, but the latter should be dragged out like a trashbag on fish night). Plagiarism is defenseless, a word-by-word or note-by-note or paint-by-number appropriation of another’s work. Plagiarism, though, is just how we think.

Researchers have long known that when creating something new, people borrow heavily from things that already exist: if asked to make up creatures to populate a foreign planet (as psychologists Thomas Ward, Richard Marsh, and their colleagues have demonstrated), we’ll all pretty much draw the sorts of creatures we have here on earth. Our creatures will have noses and ears and appendages and bilateral symmetry. And once we bestow upon a creature one earth-like feature (e.g., feathers), we’re likelier to tack on others that correlate with that feature in the real world (e.g., wings, a beak), thus filling our planet with bird-like aliens and reptile-ish aliens and insect-y aliens and not much in between.

We’re not creating so much as tweaking what we’ve already seen. Further research suggests that if we’re shown examples—aliens allegedly drawn by other participants—our menagerie begins to take on the characteristics of those examples. It’s not entirely clear whether we’re being primed to draw aliens with noses and ears after looking at other people’s eyed and eared examples, or whether we’ve shifted our category of “alien” to reflect the idea that aliens should have noses and ears. Either way, though, we’re going to produce noses and ears. And if those examples all shared a much rarer feature—a forked tongue, maybe, or spots—why, we just might produce that too. Suspicious.

It’s important to mention that we don’t know we’re doing this. Some participants in these studies were repeatedly instructed not to worry about how possible a given feature was, and some were even explicitly told to diverge from the examples they’d been shown. And these instructions helped—some. But not all that much.

Given data from more traditional laboratory tasks, though, the results aren’t surprising. In some experiments, participants have been instructed to generate as many members of a category as possible (e.g., pears, apples, and strawberries are members of the category “fruit”). Once a participant has exhausted her supply of readily produced fruits (or if a certain amount of time has passed), she’ll be presented with additional fruits—cranberries and apricots, say—that she’d been unable to freely produce. When, later, she is asked to recall the list of fruits she’d originally generated, she’ll include cranberries and apricots right along with pears and apples. As before, explicit instructions to ignore contributions from other sources go largely unheeded. Researchers call this phenomenon cryptomnesia: inadvertent plagiarism. So perhaps we should go easier on our plagiaristic peers. I had it right, many years ago, when I first wrote, “Many a man fails as an original thinker simply because his memory is too good.” Okay, okay, that was Nietzsche. Not that you’ll remember.