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If you've ever had that fleeting, mysterious sense that something new -- a city or person you’re seeing for the first time -- is somehow familiar, that you’ve been there or known them before, then you can count yourself among those who have experienced déjà vu. It’s typically a brief sensation, lasting no more than 10 to 30 seconds, but 96 percent of the population claims to have experienced at least one occurrence. source

Obviously, many people worldwide think the deja vu is real and claim to have experienced it, but has it ever been proven to exist under proper observing conditions?

If so, is there a scientific (physiological, neurological, psychological etc) explanation for the phenomenon?

Oddthinking
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Monkey Tuesday
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    Think about what you are asking: "Does [a feeling] exist?". Maybe you just want to stick with the request for an explanation. – dmckee --- ex-moderator kitten May 08 '11 at 22:07
  • In order to determine whether people have experienced something like that, you ask people. Self-reporting isn't real accurate but it's what we've got for subjective experiences. For reality...what specifically are you asking is real? Have I known a place I didn't know, and how do you test that? – David Thornley May 08 '11 at 22:47
  • Agreed: remove the first part of the question. It's about as useful as asking whether anyone has ever been truly happy. – Jon Purdy May 09 '11 at 01:32
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    It's a glitch in the [Matrix](http://www.youtube.com/watch?v=z_KmNZNT5xw), dude. – Oliver_C May 09 '11 at 10:52
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    I get it a lot in Stack Overflow... – Andrew Grimm May 09 '11 at 14:03
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    Yep, had quite a lot of them. As a little kid, I wondered if I was psychic or something, but then I realized that it didn't really work that way :D – Lagerbaer May 10 '11 at 15:13
  • It's just a glitch in your brain where you process what you're seeing as a memory, giving you the impression you've seen something before. Sort of like a short-circuit. You'll notice, for example, that it only ever happens in days following a poor night's sleep, when the brain isn't properly rested. – Django Reinhardt May 15 '11 at 16:16
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    I'm sure I've seen this question somewhere before. – matt_black Oct 01 '11 at 11:42
  • @matt_black You have seen this kind of question before, and it is just an Occam's Razor question.... Imagine you take a trip to an exotic city in a foreign country. Suddenly you are finding some of the skylines and buildings familiar. Now which explanation requires the fewest crazy assumptions (1) Reincarnation/Past Lives, (2) brain is being sucked into a Klein bottle briefly while virtual scenes are constructed for your future viewing, (3) brain is imperfectly recalling forgotten images from say, a spy movie or a news broadcast. – Paul Mar 21 '13 at 06:42
  • I get dreams that turn into deja vu. Makes it very difficult not to believe in woo. – Eva Mar 21 '13 at 08:54

1 Answers1

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From HowStuffWorks:

Deja Vu

There are more than 40 theories as to what déjà vu is and what causes it, and they range from reincarnation to glitches in our memory processes.

Déjà vu is extremely difficult to study because it occurs briefly, unannounced, only in certain people, and has no witnesses or physical manifestations other than the person saying, "Hey, déjà vu!" Because of this, there is little firm research and no definitive explanations.


Firmly placing déjà vu within the study of memory, [researchers] hope to discover more about how memories are formed, stored and retrieved.

They have since determined that the medial temporal lobe is involved in our conscious memory.


Double Perception (Divided Attention) Theory


... when we are distracted with something else, we subliminally take in what's around us but may not truly register it consciously. Then, when we are able to focus on what we are doing, those surroundings appear to already be familiar to us even when they shouldn't be.


The Hologram Theory


Dutch psychiatrist Herman Sno proposed the idea that memories are like holograms, meaning that you can recreate the entire three-dimensional image from any fragment of the whole. The smaller the fragment, however, the fuzzier the ultimate picture.

Déjà vu ... happens when some detail in the environment we are currently in (a sight, sound, smell, et cetera) is similar to some remnant of a memory of our past and our brain recreates an entire scene from that fragment.


Dual Processing (Delayed Vision) Theory


Robert Efron tested an idea at the Veterans Hospital in Boston in 1963 that stands as a valid theory today.

He proposed that a delayed neurological response causes déjà vu.

Because information enters the processing centers of the brain via more than one path, it is possible that occasionally that blending of information might not synchronize correctly.


Origin of Deja Vu pinpointed?


... a new study suggests only a small chunk of [the hippocampus, called the dentate gyrus, is responsible for “episodic” memories—information that allows us to tell similar places and situations apart.

When Susumu Tonegawa and his team bred mice without a fully-functional dentate gyrus, the rodents struggled to tell the difference between two similar but different situations.

More to read:

Oliver_C
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  • Great answer... I just wish it also explained why sometimes I not only have deja vu, but also deja vu about having deja vu about the situation. I've had that happen a few (distinct) times. I don't think I've ever gone another layer deep, though - that is, having deja vu about having deja vu about having deja vu about the current situation. – Glen O Apr 07 '15 at 16:06