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  • Have you experienced déjà vu?

  • It's that shadowy feeling you get

  • when a situation seems familiar.

  • A scene in a restaurant plays out

  • exactly as you remember.

  • The world moves like a ballet

  • you've choreographed,

  • but the sequence can't be based on a past experience

  • because you've never eaten here before.

  • This is the first time you've had clams,

  • so what's going on?

  • Unfortunately there isn't one single explanation for déjà vu.

  • The experience is brief

  • and occurs without notice,

  • making it nearly impossible

  • for scientists to record and study it.

  • Scientists can't simply sit around

  • and wait for it to happen to them --

  • this could take years.

  • It has no physical manifestations

  • and in studies, it's described by the subject

  • as a sensation or feeling.

  • Because of this lack of hard evidence,

  • there's been a surplus of speculation over the years.

  • Since Emile Boirac introduced déjà vu

  • as a French term meaning already seen,

  • more than 40 theories attempt

  • to explain this phenomenon.

  • Still, recent advancements in neuroimaging

  • and cognitive psychology narrow down

  • the field of prospects.

  • Let's walk through

  • three of today's more prevalent theories,

  • using the same restaurant setting for each.

  • First up is dual processing.

  • We'll need an action.

  • Let's go with a waiter dropping a tray of dishes.

  • As the scene unfolds,

  • your brain's hemispheres process

  • a flurry of information:

  • the waiter's flailing arms,

  • his cry for help,

  • the smell of pasta.

  • Within milliseconds,

  • this information zips through pathways

  • and is processed into a single moment.

  • Most of the time, everything is recorded in-sync.

  • However, this theory asserts

  • that déjà vu occurs when there's a slight delay

  • in information from one of these pathways.

  • The difference in arrival times

  • causes the brain to interpret the late information

  • as a separate event.

  • When it plays over the already-recorded moment,

  • it feels as if it's happened before

  • because, in a sense, it has.

  • Our next theory deals with a confusion of the past

  • rather than a mistake in the present.

  • This is the hologram theory,

  • and we'll use that tablecloth to examine it.

  • As you scan its squares,

  • a distant memory swims up

  • from deep within your brain.

  • According to the theory,

  • this is because memories are stored

  • in the form of holograms,

  • and in holograms,

  • you only need one fragment

  • to see the whole picture.

  • Your brain has identified the tablecloth

  • with one from the past,

  • maybe from your grandmother's house.

  • However, instead of remembering

  • that you've seen this pattern at your grandmother's,

  • your brain has summoned up the old memory

  • without identifying it.

  • This leaves you stuck with familiarity

  • but no recollection.

  • Although you've never been in this restaurant,

  • you've seen that tablecloth

  • but are just failing to identify it.

  • Now, look at this fork.

  • Are you paying attention?

  • Our last theory is divided attention,

  • and it states that déjà vu occurs

  • when our brain subliminally takes in an environment

  • while we're distracted by one particular object.

  • When our attention returns,

  • we feel as if we've been here before.

  • For example, just now you focused on the fork

  • and didn't observe the tablecloth

  • or the falling waiter.

  • Although your brain has been recording everything

  • in your peripheral vision,

  • it's been doing so below conscious awareness.

  • When you finally pull yourself

  • away from the fork,

  • you think you've been here before

  • because you have,

  • you just weren't paying attention.

  • While all three of these theories

  • share the common features of déjà vu,

  • none of them propose to be the conclusive source

  • of the phenomenon.

  • Still, while we wait for researchers and inventers

  • to come up with new ways

  • to capture this fleeting moment,

  • we can study the moment ourselves.

  • After all, most studies of déjà vu

  • are based on first-hand accounts,

  • so why can't one be yours?

  • The next time you get déjà vu,

  • take a moment to think about it.

  • Have you been distracted?

  • Is there a familiar object somewhere?

  • Is your brain just acting slow?

  • Or is it something else?

Have you experienced déjà vu?

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B1 TED-Ed déjà vu déjà vu brain waiter

【TED-Ed】What is déjà vu? What is déjà vu? - Michael Molina

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    Ingo Yang posted on 2014/02/09
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