Hey, Thoughty2 here. The film Groundhog day, released back in 1998,
is set in the town of Woodstock - no, not that one - and tells the story of Bill Murray’s
character Phil Connors, who repeatedly relives February 2nd. Hey, Thoughty2 here. The film Groundhog day, released back in 1998,
is set in the town of Woodstock - no, not that one - and tells the story of Bill Murray’s
character Phil Connors, who repeatedly relives February 2nd. Wait, did I do that bit already? Chances are that, like me - and good old Bill
Murray - you’ve had that strange feeling where you feel like you’ve already experienced
a situation before, even though you know you haven’t. That sensation, of course, is déjà vu, and
between 60 and 80% of us will experience it at some point in our lives. But what exactly is déjà vu, and what causes
it? Well, according to professor of psychological
science James Lampinen, déjà vu is “a strong sense of global familiarity that occurs
in a seemingly novel situation.” It’s that little nagging voice in your head
saying “I’ve been here before” when you know that’s not the case, unless you’re
eating cheese straight out of the fridge at 2am – we both know it’s not your first
time. The phenomenon was first named by a French
parapsychologist Emile Boirac in 1876. The name itself is fairly self-explanatory—déjà
vu means “already seen” in French. But why was it a parapsychologist - someone
who studies psychic phenomena - who was so interested in it? Well at the time, déjà vu was considered
so strange it was thought to be something supernatural, much like clairvoyance or mediumship. For many years, it was considered an area
unworthy of study, most often explained away as a side effect of reincarnation or possibly
even alien abduction. Never been in this room before that somehow
feels so familiar? Well then, you must have been here in a past
life, obviously! Either that or aliens vigorously probed you
on this very spot before wiping your brain. But over the years, the scientific community
has begun to take déjà vu more seriously - though the same can’t be said for the
general public - a 1991 Gallup poll of attitudes towards déjà vu saw it placed alongside
astrology, paranormal activity, and ghosts—you know, the holy trinity of ridiculous superstitious
beliefs. The name déjà vu itself has become a catchall
term for unexpected familiarity, but there are actually several different varieties of
the phenomenon to remember. Déjà entendu is the sense you’ve already
heard something that’s in fact new to you – not to be confused with Deja Nintendo,
which is when you suddenly remember you’ve been playing Pokemon for six days straight
and need to get a life. There’s also, déjà pensé, the feeling
you’ve had a particular thought before, when in reality you haven’t. Déjà gouté relates to food, and déjà
voulu, weirdly enough, is the sense you’ve desired something - or someone - before, when
you haven’t. It’s important to note that déjà vu is
completely different to precognition, which is where people have the feeling they know
what’s about to happen. That’s not déjà vu as much as it is claiming
to be psychic and mental. To be on the safe side, psychologists have
actually tested this out. Back in the 1950s, when scientists had free
rein to attach whatever they felt like to people’s brains, direct stimulation of the
frontal cortex, which induced déjà vu, was found to also produce the feeling of premonition—but
without granting any actual power to predict things or see the future in any way. And more recent, less brain-proby experiments
have found exactly the same thing. These days, we separate déjà vu into two
distinct types. The first, what we’d consider “regular”
déjà vu, is seemingly random, and the second is associated with neurological conditions
like temporal lobe epilepsy. This latter form is usually accompanied by
other symptoms and is termed pathological déjà vu. It’s caused by disease or injury of some
kind, particularly damage to or malfunction of the frontal lobe, the part of the brain
that handles memory. Pathological déjà vu is easier to study,
since it occurs far more frequently in the individuals it affects, and researchers have
been able to identify the areas of the brain where the feeling originates. But pathological déjà vu is generally considered
to be a little bit different from your normal everyday déjà vu. For instance, those suffering from this condition
may actually think they’ve been in a given situation before for sustained periods of
time, rather than merely experiencing a fleeting feeling. A British man, Pat Long, suffered from one
of the worst cases of déjà vu on record. In his mid-thirties, Pat was diagnosed with
a brain tumour the size of a lemon after suffering epileptic seizures. To most of us, déjà vu is nothing more than
a strange moment, a kind of ‘huh, that’s weird’, that lasts no more than a second
or two. Pat’s déjà vu was something else entirely. In fact, it wasn’t really déjà vu at all,
but déjà vecu, meaning ‘already lived’ - we’re building up quite the nice little
list of French vocab here, aren’t we - anyway, as the name suggests, Pat’s déjà vecu
meant he would believe he had lived whole sequences of events before. The feeling was so strong and would last so
long that for weeks on end he would be almost entirely unable to differentiate between past
experiences and the present, with memories, hallucinations, and the products of his own
imagination all interchangeable to him. Epilepsy sufferers often experience bouts
of déjà vu during seizures, as well as the experience described as the opposite of déjà
vu - jamais vu - Meaning “never seen”. Jamais vu is when a situation that should
be familiar instead feels foreign for some reason, as if you’re experiencing it for
the first time. While not quite so famous as it’s cousin
déjà vu, jamais vu is easier to induce—repeat any word aloud enough times in a short space
of time and it will slowly start to lose its meaning meaning meaning meaning meaning meaning
meaning meaning meaning meaning “meaning”…meaning? Inducing déjà vu is far more difficult,
which means studying the sensation can be tricky - that’s part of the reason we still
don’t know exactly how it works or what causes it. For most of us, it’s not a daily occurrence,
so getting data on a significant scale in a lab setting is difficult. Difficult, but not impossible. As part of a 2006 study, scientists at Leeds
Memory Group used hypnosis in an attempt to induce déjà vu. They theorised the sensation was caused by
a kind of malfunction in memory processing. When the human brain is presented with a new
scene, it carries out an internal check to see whether elements of the scene have been
observed before. If they have, a different part of the brain
identifies the scene as familiar. The researchers hypothesised that déjà vu
occurs when the second part of this process is triggered without the first, and they were
able to successfully use hypnosis to artificially trigger the malfunction simply by telling
hypnotised participants that the next time they saw a particular word, they would know
it was familiar but not know where they’d last seen it. Does that explain the mystery then? Well, not necessarily. Because other researchers attempting to recreate
déjà vu have come to their own, sometimes very different conclusions. According to a 2014 study conducted at the
University of St Andrews in Scotland, déjà vu may actually be a healthy and important
neurological failsafe that performs a conflict resolution function to prevent false memories
from forming. As part of the experiment, researchers used
word association techniques to convince participants they’d been shown certain words they hadn’t,
effectively forming simple ‘false memories’. When later quizzed on these memories, around
two thirds of participants reported experiencing déjà vu. Interestingly, MRI scans of their brains showed
activity not in the hippocampus, which is responsible for memory, but in the frontal
cortex, which is responsible for decision making. The researchers theorised that déjà vu was
experienced as the brain attempted to resolve the conflict between what the participants
had actually seen, and what they thought they’d seen. As interesting as these ingenious lab-based
explorations of déjà vu are, it’s also possible there’s a much simpler explanation
to all this - that déjà vu is simply triggered by a ‘forgotten’ memory. After all, it’s well established that less
important and infrequently accessed memories are eventually forgotten, or at least suppressed
to some extent. Déjà vu may just be the feeling we get when
something we’re experiencing is similar to one of these discarded memories that’s
gone but not-quite-forgotten. Frequent travellers are also thought to experience
déjà vu more regularly than others, which perhaps supports this theory - the more places
you’ve been and the more different things you’ve seen and done, the more likely it
is that a seemingly new experience might feel familiar to you, because it’s similar to
something you no longer quite remember - consciously, at least. We can’t talk about Déjà vu without giving
a quick shout out to Sigmund Freud, who believed the phenomenon was caused by repressed desires
or old traumatic memories, because, well, that guy linked everything to repressed desires
and trauma. He also had a suspicion that regular suffers
of déjà vu were most likely fixated with their mother’s genitals, but let’s face
it, Freud wasn’t happy until he’d gotten at least one set of genitals into each of
his theories, so we can probably take that with a pinch of salt. Saying that, there was some method to his
genital-based madness on this occasion - Freud reasoned that your mother’s ‘secret garden’
is the only place in the world every single one of us has been just once before (I would
hope). Whether or not people born by caesarian section
experience déjà vu is, so far as I’m aware, unknown. There’s a thesis subject for you budding
psychologists out there. Make sure you give me a mention in the acknowledgements. Another older explanation, albeit one that
remains a valid theory today, is known as dual processing. It suggests our experiences are handled in
both hemispheres of the brain, and any delay in processing from one side may cause that
eerie feeling of déjà vu. This was tested by Robert Efron in 1963, and
he found that the temporal lobe of the brain’s left hemisphere is where incoming information
is sorted. But he also found that the temporal lobe receives
this information both directly and after a short detour through the right hemisphere
of the brain. If, for any reason, the information traveling
through the right hemisphere is delayed at all, it could be assigned the wrong timestamp,
giving a feeling of familiarity we assume is from long ago, but is in reality from mere
moments before. This idea that déjà vu may actually be a
sense of familiarity from extremely recent events rather than past ones underpins another
possible cause of the phenomenon - divided attention. The idea here is that when your attention
is split as you experience a new situation - for example if you’re talking to a friend
as you enter a pub for the first time - it may be that you take in your surroundings
subliminally without really paying attention to them. In essence, you’re subconsciously observing
the situation faster than you consciously process it. The gap between the completion times of these
two processes isn’t noticeable enough that you’d suddenly pause like a robot without
a command… …but it is enough to think you’d experienced
the event before, since, as in the dual processing theory, you kind of already have, fractions
of a second ago. To test this, Marsh and Brown showed groups
of students photographs of various locations and asked them if they were familiar. Unbeknownst to the students, some of the images
had been flashed onto the screen just before for a very short time, only 10 to 20 milliseconds,
which was long enough for the students’ brains to pick up on the images, but not long
enough to consciously notice them. As expected, the locations that had flashed
up, like those creepy transition shots in The Ring, had wormed their way into the students’
subconscious and were recognised as familiar, even though the students had never been to
any of them. Whichever theory you like the sound of, the
truth is they’re all still just that - theories. Despite science’s best efforts, we still
don’t know for sure what causes déjà vu. One of the latest studies, published in 2019,
found that people who experienced déjà vu more frequently used different parts of their
brain to retrieve memories than people who rarely or never do.. In particular, frequent déjà vu-ers—I’m
well aware I’ve completely massacred the French language by this point—showed less
activity in their hippocampi, the so-called librarians of the brain that help consolidate
memories, suggesting that people who don’t get déjà vu may simply be those with better
memories. Equally, if you consider the fact that déjà
vu is most prevalent in people between 15 and 25 years old, perhaps it’s just a sign
that we’re not senile yet and can still tell real memories from fake ones—a comforting
thought for anyone in that age bracket, and a sobering one for all of us over the threshold. Of course, I couldn’t go this whole video
without a quick nod to the more out-there explanations, like that from the Denzel Washington
thriller appropriately titled Déjà vu, where it’s the result of FBI-sponsored time travel,
and particularly the one made famous by Keanu Reeves wearing all black. No, I’m not talking about John Wick, or
his adverts for Saint Laurent menswear, or even his red carpet appearance at the Toy
Story 4 premiere—seriously Keanu, don’t get typecast or anything. No, I’m talking about his rise to superstardom
in The Matrix. Do I need to do a spoiler alert for a 21-year-old
film? Anyway, as you doubtless remember, in the
film, Neo sees the same cat cross a doorway twice and nonchalantly comments, “oh, déjà
vu” as if seeing the world literally repeat itself before your very eyes is no big deal. His team very much disagree, jumping into
action as Trinity explains that déjà vu is usually a glitch in the matrix that happens
when they change something. And hey, if you want to take déjà vu as
evidence we’re all just motionless bodies plugged into the machine, I’m not gonna
stop you. Thanks for watching.
