How Déjà Vu Works

Does this episode seem strangely familiar? If so, you might be experiencing déjà vu, a topic that scientists are beginning to study seriously. Discover the myriad theories about how déjà vu works in this podcast from HowStuffWorks.com.

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Episode Transcript

Speaker 1 (00:00):
Brought to you by the reinvented two thousand twelve camera.
It's ready. Are you welcome to Stuff you Should Know
from house Stuff Works dot com and be sure to
check out the new Stuff you Should Know blog now
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(00:20):
of spoken word entertainment. Get a free audio book download
of your choice when you sign up today. Blog onto
audible podcast dot com slash stuff today for details. Hey,
and welcome to the podcast. I'm Josh Clark. With me
is Charles W. Chuck Bryant. Uh. And you put the
two of us together, you know that you have stuff

(00:42):
you should know? Right? That's right, Josh, as you're doing there, Chuff,
I know you're laughing because I am doing a little thing.
I have punk in my ear and I could use
a cute tip if you have one. Hey, fun fact.
Did you know that cute tips originally called baby gaze?
Baby Gaze? I don't think I knew that, but it
sounds familiar. True story story. Very cool. I like starting
off with a fact that has nothing to do with

(01:03):
our show. Sure, right, So, Chuck, speaking of having nothing
to do with our show. Um, let's talk about deja vu?
You ever had it? I have? And uh, let me
add this as a listener suggestion. Yeah. Dedicated to one
Peter Harrison of Pittman, New Jersey, Keeping It Real and
New Jersey in the Garden State. He actually had deja

(01:23):
vu when he was listening to I Believe our Exorcism podcast.
So weird the thought of it unsettling one to have
deja vu over I would think. It turns out we
had a great article on it, so away we go. Yeah,
let's do this, Chuck. You know, are you part of
the thirty percent who has reported never having all? I

(01:45):
guess just hasn't reported having deja vu? Are you part
of the sixty to seventy seventy It definitely have had
deja many, many times. I was actually surprised to find
that number was as low as it was. I thought
it'd be hovering in the nineties, you know, and then
the other people were just too late. Say you'd ever say, yeah,
I've had deja vu. It seems like something everybody would have, right, right,
or nothing familiar has ever happened to me exactly like

(02:07):
I don't pay attention to anything at all. Right, I
just watched you know, Dancing with the Stars all the time.
So um, alright, chuck, Well, let's let's start with the
nuts and bolts, shall we. Deja vu French four French
four already seen and I believe it was named by
Emil Borak, who was a French scientist, first guy to
ever study it, so he take it its name in

(02:29):
his eighteen seventy six book Leveneer decien Ces Physiques. Wow,
thank you three years under my belt, pal, I feel
like you just channeled Peppy le Pew. So deja vu,
as everyone knows is uh is a feeling that you've
seen or experienced something before when you know that you
have not. Yeah. Yeah, it's a sense of familiarity, unplaced familiarity. Right.

(02:53):
For instance, I walk into a store I've never been
in and uh see a person I've never seen. I think, wow,
this is feel eerily familiar. Yeah. What usually happens to me,
I'm part of the sixties to self reported, Um, and uh,
what happens to me usually is there's about three different
things that are going on in conjunction with one another, Like, um,

(03:14):
you know, a fish jumps in a lake, and a
woman walks by with a baby stroller and then like
as a cloud passes in front of the sun, it'll
that's how my deja vu is. And I'm like, wow,
I've been standing in the same spot watching these the
same group of things happen, and then it just kind
of passes. Interesting. I'm like, WHOA, I don't know if

(03:36):
I could categorize mine that specifically, but well done, thanks,
thank you very much. That's my deja vu. Um. But yeah,
so essentially, um, what was the guy's named war Rock? He? Uh,
he mentioned deja vu, but he didn't really go into
detail about it. The first really respected I guess scientist
to really take up the mantle was Freud, right, and

(03:58):
he basically created the theory that that was the driving
explanation behind deja vu throughout the twentieth century. Um, and
that was that he uh, he believed it were that
deja vu was the result of repressed memories. He said
that about everything everything. If it wasn't about the penis
or the vagina, it was about repressed memories and possibly

(04:20):
mother's teet. Yeah, I went to the Freud house. Did
you have a nice photo in front of it? That's
that's great side. Yeah, what what city is that? Vienna?
I am almost positive it was Vienna. We'll find out,
won't we. Yes, Yeah, trapsed around though, and all those
memories aren't firmly rooted. So there's a deja vu joke

(04:43):
in there somewhere. I just can't find it right now,
so we'll just keep going. Huh, sure, we'll edit in later.
All right. So, at some point, as we said, Freud,
you know, he deja vu explained. And then once Freud
basically was found out to be a m basically a fraud. Okay,
well U co addicted um postulator rather than maybe a

(05:03):
real scientist. In my opinion, I'm more of a young
Gian than than the Freudian. Of course, Um, I'm a doctor,
phil guy, are you? You can't go wrong with that guy. Um. Eventually,
at some point in time, the deja vu was attached
to the paranormal. I'm not entirely certain when this happened,
but you know, you you've heard that kind of thing
like it had to do with precognition. Yeah, and and

(05:26):
real scientists wouldn't They kind of just brushed it aside. Well, actually,
one one um does explain deja vu through precognitive dreams.
But we'll get to that later, right, that's right. Um,
but yeah, that that anytime you put the stank of
paranormal onto something that's arguably real, people science just turns
her back on it. They can't stand things that they
can't apply the scientific method to whether it's real or not. Right,

(05:50):
So everybody just kind of dropped, at least the scientific
community kind of dropped deja vu until our great friend,
the functional m r I was invented a k a.
The Wonder Machine, and it sparked this renewed interest in
research into into deja vu. Right. Well, yeah, because now
you can actually look at the brain function and try
and figure out the science behind it instead of just

(06:11):
doing the Freudian thing which just makes stuff up. Right. Um,
So this is really really really new research. I mean
just last several years. Right, So the jury is still
definitely out, which is good for us and our listeners
because we get to talk about a bunch of competing
theories that are super cool, and there's a lot of them.
I think they're the articles. It's like over forty theories

(06:33):
of what actually is and I think we shouldn't go
into all four this would be a four hour podcast.
But they they've basically split deja vu into two two
broad categories. Right, there's associative and biological. And which one
is associative. Well, that's the one that most people out
there probably are more familiar with. And that's when you

(06:58):
your senses are reacting and you see here, smell something
that stirs up a feeling inside you, and uh it's
you know, it's memory based, and it's very fleeting, like
ten to twenty seconds and shorter than that. Actually, yeah,
I would say less than ten. Usually is there a
baby carriage involved? Um? These this is this is a

(07:20):
deja vu among generally healthy people. Right, so we're not
we're not really attaching any real meaning to it. It's
more like a WHOA, that was cool deja vu kind
of thing. Right. The other one, biological is actually the
result of like some sort of structural impairment to the brain. Um, say, epilepsy, yeah, um,
possibly schizophrenia. Uh. And these are these episodes are much

(07:44):
more vivid um deja vu than than associative deja vu.
And uh, the people who experience biological deja vu have
much more of a tendency to attach real meaning to
it and really believe like they they're experiencing something to wise, right,
it's not like a fleeting feeling. And if you're an
epileptic and you have a case of vivid deja vu,

(08:07):
prepare for a seizure. Oh, it's it's right before the seizure,
right before. Yeah. And apparently they also smell flowers, sometimes
two or oranges, that's what I've heard. Interesting, I agree.
So those are the two broad categories. Right. Still, it
doesn't really explain anything right now, it doesn't um with
with the biology. It seems like researchers have the biological

(08:28):
explanation of deja vu down a little more pat it's
a little more medically based. Yeah, it's like a temporal
lobe malfunction possibly. Um. And actually it seems like the temple,
the temporal lobe has everything to do with deja vu,
whether it's structural or you know, associative, right, because that's
where our conscious memory is is happening basically, which would

(08:51):
be a pretty appropriate place for deja vu to take place, rightly, Um, So, basically, Uh,
there's this part called the there's a part there's a
temporal lobe region called the medial temporal lobe and um, that's,
like you said, the part that's responsible for processing conscious memory.
And there's this guy named Robert Efron, and he's a neurologist.

(09:14):
I take it of some stripe and he did some
investigation into the temporal lobe and he found that it
receives information the same sensory input twice in Yeah, and
it's still held up his valid It makes a lot
of sense. Okay, So what what Effron postulated was that

(09:36):
if we're getting the same information twice, ones direct to
the temporal lobe, which which process of sensory information. The
other one is slightly indirect. It gets routed through the
right hemisphere of the brain and then shoots over to
the to the left hemisphere of the temporal lobe within milliseconds.
But there is a delay. There's a lag. And so
what Efron said was if this delay is longer than normal,

(10:00):
extended by even a couple of milliseconds, the brain has
the potential to confuse you know what what, I guess
kind of time stamper, you know what situation or context
that this this um this century input was taken in
UM and maybe a sign uh an incorrect category Hence
we get the feeling that we've been there before, we've

(10:22):
experienced this before because we're we're confused, and that's what
deja vu is, which makes tons of sense. Pretty cool. Yeah,
that's certainly not the only uh theory of what deja
vu is, No, uh, cell phone theory, So we talk
about that. Yes, this Dr Alan Brown is a guy
who's don't on our research in this area as well,
and he did studies at Duke University and SMU Southern

(10:44):
Methodist with Elizabeth Marsh it's a lady's name. And what
they did was they worked with subliminal suggestion, which is
one of my favorite things. I think it's really cool
and interesting. Uh. They showed photographs of different locations to
students and they're gonna you know, the plan was to
ask them which ones were familiar, but before they did this,

(11:04):
they showed the same photos at subliminal speeds so like
ten of twenty milliseconds. And what happened was the brain
of course registered it and unconsciously, right unconsciously, and that
they found familiarity with these slides of locations that they've
never been to. Like they showed the people the same
picture uh once in a split second, and then later

(11:27):
on they thought that they hadn't seen it before, but
the brain had already unconsciously a process there, right, And
you got it, buddy, so and and there was an
increase in deja vu among those people. Yeah, and um,
I saw a thing on YouTube and this isn't exactly
deja vu, but this is a really cool thing. There
was a guy in England named Darren Brown. He's a
magician and mentalist, which I think is a great title. Uh,

(11:51):
And he did this, if you look up on YouTube
Darren Brown and subliminal advertising. He did the school deal
where he brought in these two advertising guys and said, hey,
I want you to come up with an advertising plan
for me based on taxidermy. And that's all he told him.
And then he sat down an envelope and said this
is my plan and don't look at it or anything
like that sealed. These guys came up with a little

(12:13):
you know, sketch and a logo and a and a tagline.
He came back in ten minutes later or however long
it was, and opened up his envelope and the logo,
the tagline, everything was really really really similar. And these guys.
These ad guys were just blown away. And then it
showed a replay of their trip to the studio where

(12:34):
they did this, and he had placed these little subliminal
suggestions everywhere. One is a little sticker on the inside
of their cab. One was on a road sign that
they passed. One was a group of students that were
wearing a T shirt with a logo that passed in
front of the car. And their brains picked all this
stuff up. It was again Darren Brown. Okay, what was

(12:54):
the name of the clip? Do you remember, Darren Brown?
Subliminal advertising, very direct and appropriate it yes, So what
are you doing there, Chuck? You okay? Well, yeah, my
ear is uh got some gunk in it? Oh yeah, yeah,
I could use a qute tip. Actually, hey, Chuck, did
you know that qute tips originally called baby gaze gay
as in g A y S. I didn't know that,

(13:16):
but that sounds familiar back in. That's what it's interesting.
Another aside. Sorry, So okay, Chuck, that cell phone theory, right,
that's what it was called. That was Alan Brown. Yeah,
so it um it applies to deja vu in that
I guess Dr Brown is saying that we are when
we're not really paying attention, when we're distracted, UM, we're

(13:40):
still processing sensory information unconsciously. So then let's say you
walk into a room and you're not really paying attention
to you're talking to somebody. Um, when you do turn
your attention to your surroundings and you start taking that
sensory and putting consciously, that's where potentially where deja vu
comes in. Because we're comparing this new conscious sensory and
put into something or brain is already familiar with him.

(14:01):
We're like, whoa, I've been here before. And they found
that some people that are stressed and have anxiety are
more prone to it. They also found that people who
are refreshed and rested are more prone to it. So yeah,
we're still getting a handle on deja vu. Right. Yeah,
one study says one thing and the other says the
exact opposite. I love those. I've got another study, beautiful,
let's hear it. It's called the hologram study. Good one. Okay,

(14:24):
So this guy's name is Hermann's no s no no W,
and he's Dutch, and um, he basically has the theory
that UM memory memories are like a hologram, right, like
a three D construct, and they are if you take it,
just a small piece of it, you can reconstruct a

(14:45):
memory from it. But if you take a very very
small fragment, the memory is not going to be completely
accurate or true. Right. So Dr Snow's theory actually I
think he's a philosopher. Maybe his theory is that, uh,
we have little snippets of memory brought back, we recall

(15:05):
them that are triggered by something familiar, but then we
reconstruct those memories incorrectly too, and we use that immediate
um experience. Uh say, getting into a car, we have
a memory that we've forgotten about a similar car um so,
but we still recall a little bit of it, but
we reconstructed around the car that we're in right now,

(15:26):
and we feel like we've been there before. He's a psychiatrist,
by the way, thank you for that. Thank you, no
listener mail on that one. Fact checking as we go. Yeah,
you're quick, chuck, thank you you got any more? Uh? Well,
I know you probably wanted to hit um the precognitive
dream thing. Yeah, and I don't remember who came up
with this one, do you. Yeah. Swiss scientist Arthur funk Houser. Okay,

(15:47):
so funk Houser with the coolest name on the planet.
He he believed that we actually have dreams that pretend
the future, if essentially very cool, um, and that it's
generally mundane stuff that we easily forget. And he actually
conducted a study I think back in nine of a

(16:08):
bunch of kids at Oxford and found that something somewhere
around like twelve point seven percent of their dreams eventually
bore a striking similarity to future events. And he said,
it's as simple as that we we have somehow have
an ability to see what's coming down the road. Uh,

(16:28):
And that's where deja vu comes from. Well, I did,
like you said, it was usually more mundane things. What
he theorized, and this makes sense too, is that if
if it wasn't mundane, were more likely to remember it
in our you know, just waking conscious right, and these
are the ones that slipped between the cracks, right, and
since it was Monday, since we can forget it. That
would explain that kind of hazy quality that um that

(16:49):
deja vu always has. You know, it's nothing's quite right
all of a sudden, it's pretty cool, yeah, uh. And
and actually, interestingly, his theory was backed up by another
study from I found similar results, except that it was
more in the ten percent of you know, dreams pretend
the future. I think it's actually ten percent of the

(17:10):
people have dreams that could not ten percent of dreams.
Are you sure? I would say ten to twelve percent
of my dreams come true. It's happening right now. You
dreamed of having a podcast with me one day check.
Should we talk about jen vu? Yes? Please? Jean vu
is the opposite of day. I know a lot of

(17:32):
people say day, but that's just kind of a funny
way to say. It is actually a real term. I
I passed over this part in the article. Fuck, I'm
not kidding. This is brand new to me. It was
not in the article. My friend, It's called supplemental research.
You should try it sometimes. No, jan vu is is
a real thing. It means never seen and uh. It's

(17:52):
when a familiar situation is not recognized. It's like face blindness.
Not really, Okay, it was worth the shot, Chuck right. Actually, Like,
have you ever had the situation where you've said a
word like over and over in your head and then
the word starts to sound funny or that happens to
me when I see it spelled right exactly. That's John

(18:12):
avou And basically what's happening there is um. The word
is just existing in its form, so the function of
meaning is lost. So weird. You're not applying the function
of meaning. So you say, um, eggs benedict fifteen times
and by the end of it, or if you write
it out fifteen times, you're gonna be thinking eggs benedict?
What are eggs and benedict? And what is hollandaise sauce?

(18:36):
This this word looks so weird. That's one example of
John don't don't forget the Canadian bacon. Chuck, who can Yeah,
I don't know. Our Canadian friends, we love your bacon.
They just call it bacon up there. Well we call
it ham. That's true. So um, so wow, Chuck, you
just you dazzled me just now. Good. Yeah, I'd like
to do that. Yeah from time to time. Well that's uh,

(18:58):
that's sto, I guess for now, until you know, somebody
finally cements down exactly what's going on. And again, I
think the Wonder Machine is going to be the the
utility that does it for us. Je vu all over again,
as uh Yogi Barrow went said, great man, Um and Chuck,
I think it's time to say hey to the people
at audible. Audible dot com are one of our beloved sponsors.

(19:22):
Even better than that, let's tell everybody that the people
at Audible are trying to say hey, it's all of
our listeners. If they go right now, UM to audible
podcast dot com slash stuff and sign up, they'll get
one free download. And this is actually kind of big.
They have fifty tho plus titles on the site. You
can get a book if you want. Yeah, you can

(19:44):
get stand up and actually, um, I was looking on
the site and they have a bunch of George Carlin
and specifically a Place for My Stuff are arguably his
greatest work ever. Um it's my personal favorite. Um. So yeah,
there's all sorts of it's not just audiobooks, yeah Carlin.
And speaking of which, this is an audiobook either and
I'm surprised you didn't pick this one. It's your your plug.

(20:06):
But maybe the Gonzo Tapes the Life and Work of
Dr Hunter S. Thompson. These were just recently released and
these are just it's a long series, I believe that's
an abridge version on audible dot com about but you
get about six hours worth of famous author extraordinary Hunter
S Thompson uh speaking into a tape recorder. Over the

(20:27):
years he did this and they've gathered all these tapes
and it's really really awesome. I have found my one
free download. So what I will be doing is going
to audible podcast dot com slash stuff in signing up. So, Chuck,
I know you love plugging the blog. You want to
you want to take the opportunity. Sure, I would like

(20:49):
to direct everyone to our new blog, which is a
Internet term for blogged, and Josh and I write on
this sing a couple of times a day and we
talk about cool stuff. And basically the idea here was
to get the stuff you should Know Nation involved with
each other and leading comments and talking to each other
and reading about cool stuff that they should know, uh,

(21:11):
instead of just listening to us say it. And also,
don't forget to join these stuff you should Know Nation.
We are actually buying a plot of land right um.
We'll be sending details out via our blog ironically enough,
and you can access it through the homepage on how
stuff works dot com. Oh yeah, and it's called stuff
you should know. Yeah, yeah, appropriately enough and you can

(21:32):
see lovely photo of Josh who looks cute as a
dang button and chunking his black cap. That's right, so
looking good. It's good stuff. So now, yeah, there's a
blog plug. Let's do listener man, right, you ready for this? Josh?
I was born ready, Chuck. I have a couple of
stuff we should know, which our new nicer name for corrections. Um,

(21:57):
christ I thought it was stuff we should have known. Sure,
it sounds good. Christine Lee of Toronto, Ontario. And as
a quick side note, I can't remember his name, but
we had a Canadian friend right in and say it
really bugs when we say like Montreal, Canada. He said
they'd be like saying Atlanta, United States. So we need
to start saying the prob So Christine Lee is of

(22:19):
Korean descent, and she said in the Friday thirteenth podcast,
we talked about unlucky numbers in China and Japan and
again and can people die a fright? We talked about
the same thing and it's actually true in Korea as well,
and she feels like Koreans are often slighted uh to
their Chinese and Japanese friends, so we need to start

(22:40):
looking into other Asian countries. Basically, yes, apparently four is
an unlucky number in Korea, and thank you Christine Lee
for that. Sorry Christine and Chris from Pennsylvania. This is
what you're gonna love this one. Uh, he said he
listened to the Comas podcast. I'm surprised that between Josh's
Magnum p I knowledge and Ucks movie knowledge that you

(23:00):
guys never brought up the connection between Magnum in the
nine movie Coma. Tom Selleck was actually in that movie,
and I haven't seen it in years, but I remember
him being one of the Comma patients that was suspended
on wires, and that is indeed true. I don't remember
Tom Selleck in now when my earliest memory of Tom
Sellek in a movie was a Looker. No, he wasn't

(23:22):
in it. Okay, what was the other one with the
robots in? Right? You're thinking of Runaway? Very nice? Yeah?
Are you sure he wasn't in Looker? Yeah? That was
Albert Finney. That was a great movie though for an
eighties sci fi. I agree. Susan Day's in it too. Yeah.
All right, well we should probably get out of here
before Chuck and I say something to embarrass ourselves right further. Yeah, um,

(23:45):
so thanks for listening. Uh. I would advise everybody to
go onto the site and um check out how deja
vu works by an article written by our colleague leanne Opringer.
There's a nice little easter egg hidden in the article
that may induce deja vu in you. You can find
that by typing in how deja vu works in our

(24:05):
handy search bar how stuff works dot com And if
you want to send Chuck in I a message via
electronic mail, a non haiku related message, Yes Chuck, yes,
non haiku. You can alert us at stuff podcast at
how stuff works dot com for more on this and

(24:28):
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