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What Causes Deja Vu?

memory, repeated experience
What deja vu is and what causes it is a mystery. (Image credit: Dreamstime.)

That distinct illusion of having been there and done that has no explanation. The parapsychologist will tell you it's a past life experience. Yogi Berra will remind you it seems like you've felt it before. And most scientists will throw their hands up.

Some believe déjà vu involves emotional responses to similar events; others figure the brain short circuits, sending an event to memory just a split second before putting it into consciousness.

Its fleeting nature makes déjà vu about as easy to study as the afterlife. Some people have a chronic variety, though, and so one study is attempting to get inside their minds. Chris Moulin, who runs a memory clinic at the University of Leeds in the UK and is doing the research, describes one patient who illustrates how déjà vu might be related to memories being mixed up by the brain: "When this particular patient's wife asked what was going to happen next on a TV program he'd claimed to have already seen, he said, 'How should I know? I have a memory problem!'"

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Robert Roy Britt
Rob was a writer and editor at Space.com starting in 1999. He served as managing editor of Live Science at its launch in 2004. He is now Chief Content Officer overseeing media properties for the sites’ parent company, Purch. Prior to joining the company, Rob was an editor at The Star-Ledger in New Jersey, and in 1998 he was founder and editor of the science news website ExploreZone. He has a journalism degree from Humboldt State University in California.