I love déjà vu in the same way that I love sneezes and
yawning and blind spots and dreams and migraines. These things all make me very happy. They’re small reminders that my brain is still
there, it’s organic, it does things I can’t predict. They point out that we are laughably unaware
of the mucky mushy underpinnings of our lofty cognitive musings. Déjà vu makes us remember we’re only human.
Well, maybe that’s not true for everyone. Déjà vu means different things to different
people. What it certainly is not is a literal re-experiencing of a
moment that happened in that exact same way at some previously unspecified
time. This is an incorrect
interpretation of the phrase, because even though the direct translation of
“déjà vu” is “already seen,” the definition of the word includes the notion
that one is re-seeing something one knows one couldn’t possibly have seen before.
Now, some say that déjà vu is some special form of
extra-sensory perception, or it’s a signal the Matrix has been altered, or it
tells us things about our past lives, or it’s some sort of breakdown between
all the versions of our lives we’re simultaneously living. Here’s the thing. Déjà vu is already a beautiful miracle without making it anything paranormal or
supersensory. It’s a truly incredible
process and a delightful experience.
This may sound weird coming from an urban fantasy writer, but I just
don’t like the taste of forcing supernatural elements where they don’t belong.
Scientific theories posit numerous explanations for déjà
vu, most having to do with the medial temporal lobe (remember the
hippocampus…?). Keep in mind that
researchers very rarely have the opportunity to study déjà vu, given how
transient and unpredictable it is – in fact, apparently only about 60-70% of
people report having ever experienced the phenomenon at all (yet another
variable thing I thought was common to everyone!). So even some of the so-called “scientific
research” discussed here tends to wax philosophical.
According to these researchers, déjà vu may occur
because:
(1) Some aspect of the current experience excites the
brain pathways that produce a sense of familiarity with the event, but not those that support proper
recollection of a previous event, creating a disconnect that makes us feel like we know it without being able
to pull out exactly when or where we experienced it before.
(2) Our brains probably store memory in such a way that a
small stimulus (a smell, a color) can trigger the incomplete recall of a real
but different memory… and in some cases this might give us a sense that the
current experience has already been experienced. (The first part of this is certain – it’s the
second that’s up in the air.)
(3) Our two brain hemispheres might sometimes get
slightly out of sync when processing an input, such that one side gets that
direct input fractions of a second earlier than usual and therefore
misinterprets the added information from the other half of the brain as a
repeat of an already-experienced memory.
(4) We “experience” many types of things in media like
books and movies, which allow us to feel strong familiarity for things we’ve
never actually experienced in real life – and when we see it in real life for
the first time we might accidentally think we’ve already seen it.
Alternatively,
(5) Some researchers believe that precognitive dreams
(i.e. dreams which predict future events) may create a sense of déjà vu later on
when they are properly experienced. I’ll
tackle this one shortly.
(6) And lastly – and this is the least controversial of
the theories because it’s the most testable – déjà vu can occur as a result of
an epileptic event, like a seizure, in the medial temporal lobe.
(There are plenty of other theories I’ve decided to let
you discover on your own, seeing how long that paragraph has become already.)
I like aspects of a lot of these, but I want to put my
money down on the first and last – the disembodied familiarity thing and the
seizure thing.
There’s a lot of evidence that one’s concrete knowledge
of a previously-experienced event (call it recollection)
and one’s comparatively vague sense of familiarity
with an event are different things that are processed differently by different
brain regions – recollection by the hippocampus, and familiarity by… well,
parahippocampal and/or perirhinal cortex, depending on who you talk to (they’re
both structures basically adjacent to the hippocampus). In the rare déjà vu experience, it’s possible
that something about the current environment differentially stimulates the
familiarity and recognition brain structures, creating a detached sense of familiarity.
Notice that in the previous sentence, I said it was
something about the external environment causing the brain
activation. But it’s also possible that
your brain just does this stuff to itself, without any outside help. For example, people with temporal lobe
epilepsy sometimes report feeling déjà vu right before a seizure strikes. But you don’t have to have epilepsy to have epileptiform
brain activity, and in fact every single person on the planet has endured some
level of seizure-like activity in his or her brain. Basically, every once in a while some tiny
group of neurons goes a little haywire and activates for no good reason, but
it’s natural and nothing to worry about.
Mostly these events don’t impact our conscious lives at all. But maybe,
sometimes these events occur in just the right place at the right time,
activating our familiarity structures out of the blue, and suddenly the whole
world around us feels like we’ve done it before.
Regardless of whether it’s externally or internally
generated, it makes sense that déjà vu is an innocent brain mistake which makes
us feel something that’s not really real.
It helps explain why we sometimes feel recursive déjà vu – the sense
that we’ve even had this particular sense of déjà vu before, and that we’ve had
a déjà vu of that déjà vu of a déjà vu, and so forth. That’s just our brain accidentally and
repeatedly triggering a feeling that this event has occurred before when it
hasn’t. So I’m pretty darn confident
that when you experience déjà vu, that exact experience has never happened to
you before – no matter how much you want to believe that. That want, that need – that’s just your brain talking.
Which brings me to precognitive dreams. I will certainly insult people with my
opinion about this, but I’m willing to take that hit and say that the ability
to actually foresee future events in a dream is literally impossible. Let me rephrase that so I can be totally
clear – precognitive dreams cannot be
the true experience of a real-life event before it happens.
There are just too many problems with the idea that dreams
can be pre-plays of real events (not least the violation of causality). I’ll name a small few. (1) The vast majority of things that happen
to us happen repeatedly, so it’s practically impossible to avoid dreaming up scenarios which will be similar to later life
events; also, “similar” is not at all the same as “identical”. (2) If you compare every dream that you’ve
ever dreamed with every event that has ever happened to you, you will
absolutely come up with matches, and it has nothing to do with foreseeing
anything. (3) Our brains can make us feel conviction about things we
actually can’t remember very well, so when those similar real events happen we
can be duped into accidentally overwriting our dreams to match the events
(someday I’ll write a post about this point).
Okay, enough of that.
I don’t want to give the impression I don’t believe dreams can be predictive. Brains are prediction machines. Especially human
ones. It’s arguably what we do best. So it’s totally reasonable that your brain
makes very, very good predictions
about the future while you’re dreaming, using information you might not
consciously piece together while going about your daily. I am a happy believer when someone tells me
that they always dream of a white elephant before someone dies – so long as
they also tell me the white elephant is their brain’s way of assimilating a
host of (subconscious) clues indicating those other people were about to
die. Such a dream would be entirely
plausible, and maybe even probable.
What I’m saying is that déjà vu serves as a reminder that
our brains are doing a lot of things behind the scenes. In fact we don’t have conscious access to the
majority of the things our brains do.
(Go ahead, try and stop your heart just
by thinking it.) When magical things
like déjà vu and prescient dreams happen to us, we can congratulate our brains
for being so gosh-darn brilliant without us even knowing it. They really are capable of miraculous feats.
P.S. I got really sick of seeing the phrase “déjà vu all
over again” in article titles as I looked all this up. I used to love saying that and now it’s
tainted for me forever. So sad…
I think I've read this before....
ReplyDeleteJust kidding, obviously. You are brilliant, and I love your take on things.
WKS.
Let me be more substantive. I have always been quite fascinated by the workings of the brain. There is a statistic quoted repeatedly and so much so that it has become trite to my ears, and I don't even know if it is true. Something to the effect that our brains are only being utilized by about 10%, imagine what we could do if we could access the other 90%. But in my less educated mind, that doesn't make a lot of sense because of course it is in use...
ReplyDeletePlease explain...
BAH that drives me CRAZY! This notion came about because when we first started imaging brains, the blobs that light up during any given task are overlaid on only a small portion of the total brain. You know why? Because different parts of our brains do different things. When you're having people tell you whether a shape is a square or a circle, is the part of their brain involved in complex emotional regulation, or in auditory discrimination, really expected to light up? HELL no. You're only using 10% of your brain because you're only asking it to process 10% of the kinds of things it can process. And a lot of these processes are mutually exclusive - you wouldn't WANT more than 10% to light up.
ReplyDeleteYou know what happens when you access the other 90%? EPILEPSY. Freaking epilepsy. That's the definition of epilepsy. If you want to have a gran mal seizure, go right ahead and "access 100% of your brain" all at once. Yeesh.
I should write a post about this :)
DeleteI knew it was something like that. I'm almost as smart as you! Maybe I should be a doctor too. ;)
DeleteSeriously... these informative posts are freakin fantastic, just so you know.
ReplyDeleteThank you!! :D
DeleteKaitlin you never cease to amaze me. Thank you.
ReplyDeleteArgg... I didn't mean to be anonymous but I can't seem to post here any other way. It's me, Judi.
ReplyDeleteThank you! <3
Delete