Almost everyone's experienced deja vu — that brain-tickling illusion of having previously
experienced something that, in reality, is being encountered for the first time.
In fact, researchers at Texas A&M estimate that the trippy sensation is experienced by
roughly 60 to 80 percent of the population.
And yet deja vu remains an unsolved mystery.
But there are some pretty good theories out there —- some of which you may have heard
before ….
"Talk about deja vu!"
The human brain is a seriously complex piece of biological machinery.
It's capable of processing vast amounts of information while simultaneously keeping your
heart and lungs functioning, all with no conscious input on your part.
And yet, your brain is not infallible.
According to the neuroscience experts over at Texas A&M, one of the prevailing theories
about deja vu has to do with shortcuts in neural pathways.
It's possible that when you experience something that recalls a fragment of an old memory,
your brain interprets the new experience as something it needs to place in long-term memory
rather than the short-term memory slot it would normally be placed in.
Then, when your brain accesses the information in long-term memory, it may feel like its
accessing an experience from the past, rather than something that's happening in the present.
That might be just enough to produce that strange sensation...
"What did you say?"
"What?"
It might sound like a bad thing, but your brain is actually being efficient when it
suppresses old memories.
It's really not very useful, for example, to remember things like what you had for dinner
on a random night in the year 2000.
Unless you need an alibi for that night, that kind of information is just useless clutter
that can interfere with the processing of more relevant information.
According to Anne Cleary, a cognitive psychology professor at Colorado State University, those
old memories might still play a role, if not a very useful one.
Something you did long time ago and totally forgot about might still be lingering in some
remote part of your brain where it can trigger a strong sense of familiarity even though
you can't recall any of the details.
Places might do that, too.
Maybe you're visiting a location you saw in a documentary a decade ago, but your brain
suppressed that memory, leaving only deja vu behind.
Your not-infallible brain may also get confused when it's trying to process multiple pieces
of information.
Sometimes, there's just too much information in your environment and you simply can't process
it all.
"Look!
There's inductive reasoning.
There's deja vu.
There's language processing.
There's deja vu."
Some scientists, such as Dr. Alice Medalia from Columbia University Medical Center, think
that something similar might be happening when you experience deja vu — perhaps your
brain, in the moment, is simply unable to properly process multiple pieces of information,
so it falls into that good ol' deja vu feeling.
Just like computers, brains can "glitch," too, and when your brain glitches the end
result may be that weird feeling of deja vu.
According to researchers at Texas A&M, your brain stores memories in the same part of
the brain that's responsible for the detection of familiar places, people, and events.
So you might be getting deja vu because for just a moment, your brain malfunctions.
"... and Deja Vu."
"Have we not met before, monsieur?"
"I don't think so.”
It's possible that, for whatever reason, the neurons responsible for the detection of familiarity
are firing even though there isn't anything familiar in the environment, which might lead
to the sensation that you're experiencing the past when you're solidly in the present.
"Do you ever have deja vu, Mrs. Lancaster?"
"I don't think so, but I could check with the kitchen!"
"No, that's okay.
Thank you."
Or, deja vu could be caused by something even weirder: No, it's not tiny lightning.
It's your brain forming "fake memories," or real memories that fail to form correctly.
It's possible that your brain may, for reasons that aren't totally clear, create the memory
of an experience two times.
And if you've got two different memories of the same event and you're trying to interpret
that rationally, the only logical conclusion you can really come to is that you've somehow
experienced that event before.
And that's when the deja vu hits.
Let's say you sit down for lunch at a diner you've never been to before and there's a
familiar song playing on the radio.
Once upon a time, many years earlier, you sat down at a different diner that was playing
the same familiar song.
That's not the sort of thing you would file away in your brain's catalog of information,
but the experience lingers in your memory.
Then, when you have that vaguely similar experience, your brain takes that small fragment of memory
and uses it to reconstruct a memory featuring all five senses.
This is called the "hologram" theory because it's sort of like your brain is reconstructing
a three-dimensional event out of a one-dimensional memory fragment.
It's filling in the blanks either with details it has completely fabricated or perhaps details
taken from a different experience or even a work of fiction you once read or saw on
a screen.
Even though the details aren't accurate, your brain may confuse them for a real memory,
which can trigger the deja vu sensation.
In 2016, a team of researchers at the University of St. Andrews in Scotland figured out how
to use word association games to trick people's brains into lying to them and thereby sort
of getting deja vu in a lab setting.
They then studied the regions of the brain that were active as their subjects experienced
the sensation.
According to New Scientist, the team's findings were inconsistent with the "fake memories"
theory of deja vu.
If deja vu were indeed a function of memory, you would expect to see brain activity in
the parts of the brain responsible for memory, but that's not what the research found.
Instead, scans found that the frontal parts of the brain were active during the deja vu
experience, and that part of the brain isn't responsible for memory, it's responsible for
decision-making.
The lead researcher involved with the study thinks the brain is simply checking the thing
you've just experienced against the things you think you've experienced.
If there's a conflict or memory error, it sends a signal, which could be interpreted
as a deja vu sensation.
Deja vu is a lot more common in young people than it is in older people, generally speaking.
According to Scientific American, the deja vu experience maxes out sometime between the
ages of 15 and 25 and then tapers off until it's a rare or nonexistent later in life.
Some scientists think this might be because deja vu is actually a symptom of a healthy
brain, one that is actively checking memories against experiences and filing everything
away for future reference.
It's even possible that, as we age, we continue to experience deja vu, but we just don't recognize
it as deja vu because our brains don't acknowledge the difference between a false memory and
a real one.
So that's not actually great news for the above-25 set because fewer deja vu experiences
might mean a deteriorating brain.
So if you're 25 and under, enjoy that trippy deja vu experience while you can.
As for the rest of us, welcome to possible cognitive decline.
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