Deja vu: why do I feel like we’ve done this episode before...

Hey guys, Tara here for Dnews - and most, if not all of us, have at some point or another,

experienced deja vu. It’s that familiar feeling that you’ve somehow experienced

this moment before - and even though a lot of people claim it has a spiritual basis,

perhaps linked to reincarnation - there’s actually a number of scientific theories as

to why we experience it.

The term Deja vu - which translates to “already seen” - was first coined in 1876 by French

philosopher Emile Boirac. And in the years since then, researchers studying the phenomenon

- have come up with several different types of deja vu that people experience. In general,

though - it’s lumped into one of two categories.

There’s associative deja vu, which is the most common type that’s usually experienced

by healthy people. And then there’s biological deja vu - which is almost exclusively experienced

by people with epilepsy. Often times, they say it occurs immediately before having a

seizure. And that medical basis actually makes it a lot easier to study than associative

deja vu, which relies entirely on secondhand experiences.

For most of the 20th century, researchers relied on the paramnesia theory to explain

deja vu. It was an idea proposed by Sigmund Freud, that said the phenomenon was likely

caused by repressed memories of a stressful event, that people couldn’t access anymore,

as part of their regular memory.

It wasn’t until recently, when things like brain imaging became standard, that real scientific

research - and not just speculation - was poured into the subject.

Nowadays, it’s widely agreed that the medial temporal lobe - the part of our brain involved

in conscious memory - plays a significant role in deja vu. This region happens to contain

the hippocampus, and more specifically, the parahippocampal gyrus - which is what enables

us to determine what's familiar and what isn't. Of course, knowing that this part of the brain

is related to deja vu - still doesn’t explain why we experience it. So in attempt to explain

that, Dr. Alan Brown from Duke University, concocted something called the Cell Phone

Theory, which revolves around the idea of subliminal cues.

In his study, he showed a group of students a series of photographs of various locations

- none of which they’d actually been to - and then he asked them how familiar those

locations were. Just beforehand, though, he flashed SOME of the photos on a screen for

10-20 milliseconds - which is just long enough for their brains to register it, but not enough

to actually be consciously aware of what they saw.

Sure enough, the images that were subconsciously flashed - appeared more familiar to the students,

than ones that weren’t. And those findings, he argued, could be applied to deja vu. The

idea being that whenever we feel like we’ve seen or done something before, it’s because

we have - but during that prior experience, our brains were distracted - allowing us to

subconsciously process that moment, without actually remembering that we experienced it.

Seems solid enough, but that is just one theory, of many. There’s another one, called the

Hologram Theory, proposed by Dutch psychiatrist Hermon Sno, that likens humans memories to

holograms, in the sense that our brains are capable of constructing whole 3D images from

smaller fragments of other memories. So for example, if we were to step into a room that

looks similar to a room we’ve been in before - then our brains might reconstruct an entire

false scenario based around that one memory fragment.

Again, an entirely plausible theory. But there are some different ones out there - like the

Dual Processing theory - which claims that past experiences actually have nothing to

do with deja vu, and instead, chalk it up to a delayed neurological response. The idea

behind this one, is that because there are multiple pathways through which our brains

process incoming information, it’s possible that those pathways may not always synchronize

correctly. So any delay between the time it takes for our left brain hemisphere and our

right brain hemisphere to process information, could force our brains to register something

we’ve JUST seen, as a previous memory.

Of course, like most areas of science, there’s really no simple explanation as to why we

experience deja vu. These are just three, of the hundreds of theories out there - and

of which seem equally plausible. Still interesting to think about though!

And who knows, maybe you guys have some theories of your own. Or at the very least, interesting

stories to share. If so, just leave em in the comments below, and as always - thank

you guys for watching!