What It Might Mean If You Get Deja Vu A Lot

In 1999, a 42-year-old woman went to the doctor for what she described as a popping noise in both her ears. The noise was so loud it had started to keep her up at night. The woman was diagnosed with Palatal Tremor, a movement disorder of some of the muscles at the back of the throat, in which they contract and cause a clicking sound.

She was given relaxant drugs like diazepam, but they didn’t work. In 2004, still in search of an effective treatment, the woman saw a neurologist who gave her 5-HTP, a naturally occurring amino acid that affects the central nervous system. It made the popping go away, but brought on a strange side effect.

“When I watched TV, I felt I was watching repeats, although I knew I wasn’t, as it was the news,” she wrote at the time (her account was later documented in a 2007 case report). “I then got a phone call from my sister to tell me the kids were being sent home as there was a power cut at school. I asked her why she was telling me this again as she had told me this several days before.”

But her sister hadn’t told her that before, and there hadn’t been a power outage at the school a few days earlier. Instead, the woman was having an extreme, and long-lasting, episode of déjà vu.

“Since the doctor did not think it was the pills, I decided to try again,” she wrote. “I had the same feeling of having seen and done all of this before. I did not have any eerie type of feeling, I knew I couldn’t know these things but I felt like I did.”

Déjà vu is French for already seen. It’s thought to be very common, having occurred in between 30 and 96 percent of the population, and usually lasts only seconds. It can be triggered by fatigue or emotional stress and is most frequent in our 30s, tapering off after that. People report more déjà vu the more years of education they’ve had. It’s more common at night than in the morning. People who travel regularly and people who remember their dreams are more prone to déjà vu.

We know déjà vu as a weird fleeting moment. You pause and bask in the strangeness, then move on—perhaps not to feel it again for months or years. We brush it off in our daily lives but déjà vu, says Adam Zeman, a clinical neurologist at the University of Exeter in the UK, can be a window into the many ways our brain regulates memory, familiarity, and other related processes. (From this particular patient, Zeman says, we may have learned that serotonin is involved in the genesis of déjà vu; the drugs she was taking were serotonergic, and they triggered the episodes.)

Zeman says that even though we tend to lump déjà-vu-like experiences together, researchers are now distinguishing between different kinds of déjà vu. Some are so intense you might realize you have never experienced them, even if you consider yourself a déjà vu veteran.

With déjà vu, we get an eerie sense that our surroundings or current experiences are familiar, but we simultaneously recognize there’s something “slightly bogus” about that familiarity, Zeman tells me.

But déjà vu has also long been recognized as an aura of temporal lobe epilepsy, or the beginning of a seizure. For a person with epilepsy, a feeling of déjà vu can mean they will soon start seizing or lose consciousness. Zeman collaborated on a study a few years ago that asked whether there was anything about an epileptic’s déjà vu that was different from déjà vu experienced by a healthy brain; the answer seems to be no. It might be slightly more drawn out or occur more frequently in epileptic people, but it’s otherwise the same.

Zeman says that because scientists are sometimes able to record directly from the brains of people with epilepsy—they have more reasons to undergo neurosurgery, after all—we’ve been able to determine which parts of the brain are associated with déjà vu. In the late 1950s, researchers found through electrical stimulation and recording of seizures that the temporal neocortex was primarily involved. In the late 1970s, it was shown that you could provoke déjà vu through electrodes in the medial temporal lobe, and more recent work has found with even more specificity which parts of the medial temporal lobe are associated with déjà vu.

The medial temporal lobe includes the hippocampus and the parahippocampal gyrus, both of which are important in memory. The famous patient HM had epilepsy in both of his medial temporal lobes, and they were removed to stop his seizures. Back then, it wasn’t known how crucial those brain regions were, and HM’s life essentially came to a grinding halt. He was unable to form any new conscious memories from then on, not remembering the doctors and others who came to treat or visit him.

I had always assumed that déjà vu was a phenomenon of the hippocampus, our main memory center. But Zeman says that it more likely involves an adjacent area, called the perirhinal cortex, which allows us to recognize when things are familiar.

“Say your boss comes into the room and you look up—you have an immediate familiarity response,” Zeman says. That’s a little different from recollection, which would be like you asking yourself when you last saw your boss.”

The current theory is that epileptic déjà vu is caused by abnormal discharges of electricity in that familiarity region. When that area is hyperactive, you feel familiarity that’s not accompanied by recollection—which is why it feels so weird.

“Maybe you’re sitting in a café where you’ve never been before, you get activity in the familiarity area, and suddenly the whole experience of sitting there seems intensely familiar, but you have no way of justifying that because you can’t,” he says. “Because you have never been there before. You can’t fish out a memory. That’s why this strange combination leads to the feeling that the familiarity is false.”

I tell Zeman that it sounds to me like the opposite of Capgras syndrome, or imposter syndrome—when you think that people who you know, like your spouse or best friend—are actually imposters. But Zeman corrects me again, and reveals how subtly varied these concepts are in the brain—even seemingly basic tasks like seeing and recognizing people.

In Capgras syndrome, it’s actually the amygdala, which is involved in emotional judgments, that goes awry, he says. You can recognize someone as familiar, but not have that supported by the right emotions, the ones you would normally feel looking at your husband, wife, or friend. “It might lead you to the conclusion that your relative must’ve been replaced by somebody else,” he explains. “They look as they should, but they don’t feel as they should.”

I tend to enjoy getting déjà vu. It has a way of making even the most mundane details take on a magical air. But Zeman says that people with epilepsy can be bothered by it. Not only is their experience of it heightened, and often longer, it can also be accompanied by fear and anxiety, since it is usually followed by a full-blown seizure.

How can this warning bell for a seizure manifest in people who don’t have epilepsy? Zeman says we don’t completely know. One theory is that ordinary déjà vu is a kind of seizure that healthy people experience. (Wilder Penfield, a famed Canadian neurosurgeon even called déjà vu “little seizures.”)

But that idea isn’t widely accepted by many neuroscientists, and it’s hard to find any evidence for it because most healthy people don’t get intracranial brain recordings. One study that Zeman collaborated on found that there might be a subtle reduction in volume in areas like the medial temporal lobe in healthy people who experience déjà vu, compared to those who said they’d never had it. There’s some thought that a change in the structure of their brain might explain how a person without epilepsy could have déjà vu.

“But I think that the truthful answer,” he says, “is that we still don’t know what the underlying mechanism of normal physiological déjà vu is.”

Chris Moulin’s patient was a man in his 80s who had been diagnosed with Alzheimer’s, but didn’t have the typical symptoms.

He wasn’t forgetful; in fact, he claimed that everything he did he had already done: He wouldn’t watch TV because he said he had seen all the shows before; he refused to read the newspaper because “even the news seemed the same,” Moulin remembers. The man said he had already met Moulin before, too. He had already done all the tests Moulin was doing on him, had been asked all of the questions Moulin was asking him. He appeared to be stuck in some kind of time loop.

Moulin, a cognitive neuropsychologist at Université Grenoble Alpes, is now one of the leading researchers in déjà vu today. He became interested in déjà vu when, after meeting this man, he consulted his handbook of memory disorders and found no details on it, aside from a small mention of temporal lobe epilepsy.

“That started a kind of accidental career in déjà vu,” he tells me. “I am a memory researcher, and do other things. I used to say that was my day job, and my hobby was déjà vu, but now the déjà vu is slowly taking over.”

Moulin says this man represented an extreme case. Now that he’s been studying déjà vu for a while, he makes the distinction between those who know that their sense of familiarity can’t be right, and those who think they truly have experienced a given moment before.

“Typically, when we have déjà vu we know that there’s something at fault,” Moulin says. “We know that we’re finding something familiar but it soon passes and we think, ‘Oh, that was strange.’ There’s a conflict in our interpretations. But some people are seduced by their feelings of familiarity so they really do think that they had the conversation before. Then they justify reasons for how they could have had the conversation before, or read the newspaper before, and they invent stories to justify this strong belief. This is a memory disorder called confabulation.”

The confabulations of the man with Alzheimer’s went like this: When his wife would bring him the paper in the morning, and he wouldn’t read it, he would say, “When you were asleep in bed, I actually got up, went to the newsstand, and they were unloading the newspaper from the newspaper shop, and that’s how I already read it. Then I snuck back in the house, came back to bed, and then went back to sleep.” Of course, none of it was true. It was a way for him to explain to himself how the paper seemed so overwhelmingly familiar.

In general, Moulin thinks that there is probably a spectrum of déjà vu, from the intensity of the experience itself to how much you know it to be false. In healthy people, he now considers being able to recognize when you have déjà vu a healthy symptom. If you feel that something is overly familiar, but you know that’s not right, it’s a sign that you’re highly cognizant of what’s going on in your brain.

Moulin tells me that the latest theories on déjà vu involve other parts of the brain aside from just the familiarity regions. He says that the temporal-lobe hypothesis came about largely because you can artificially induce déjà vu by stimulating those areas. But Moulin thinks that might not be enough. Over-activity just in the familiarity areas would lead only to a feeling of familiarity—like thinking you know somebody on the street when you don’t. But the typical déjà vu isn’t only familiarity but also the self-awareness that that familiarity is false.

That bit of it—the awareness part—led Moulin and others to think the prefrontal cortex is involved too, as a kind of control mechanism that helps monitor and organize the entire memory system. In the case of déjà vu, the prefrontal cortex is watching what’s going on in the memory regions, and then detects a conflict between what’s logically possible and what the memory system is saying is familiar. “That again fits in with this story that normal déjà vu is a healthy thing,” Moulin says—because your prefrontal cortex is astute enough to notice that this over-activity in the memory system isn’t quite right.

“Young people get it more than old people get it,” he says. “I think as you get older, you lose the precision in the memory system and the fine-grained control of what’s happening in that system. One journalist I talked to described it as a fact-checking system, and I really like that idea: That déjà vu is just a sign that there’s something to stop you getting carried away with your sense of familiarity.”

Moulin distinguishes between two kind of déjà vu’s, which have been accepted by other déjà vu researchers. One is the classic déjà vu—a sense of familiarity with your current experience that you know is false.

The second kind, Moulin calls déjà vécu, which translates to already lived. People with déjà vécu don’t only feel as if something is familiar, it really seems that they have lived that moment before, and that they know what will happen next—but still with an overarching knowledge that those memories can’t be real. (This is unlike confabulation, which has no self-awareness that the experiences a person remembers never happened.) Déjà vécu can include recalled fragments of memories, “as if you’re on the verge of actually pinpointing the déjà vu and it may be combined with a feeling that you can sense the future,” he says.

These two different experiences might implicate different brain regions: While déjà vu is coming from the perirhinal cortex, or the familiarity region, déjà vécu might be involving the hippocampus, because it’s more like an actual false recollection.

Zeman says he has seen several people whose experiences fit the description of déjà vécu more than déjà vu, because they are so overpowering. Like Shona, a woman in her mid-twenties who woke up one morning, ate breakfast, got ready for work, but felt she was “acting in a film that she had seen before.”

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“She felt she had lived just these same moments, just this same day before,” Zeman describes in his book, Portrait of the Brain. “She was mysteriously caught up in a repeat performance, point for point: throughout the day she had the sense of knowing precisely what would happen next.”

After several days of constant déjà vu, Shona got medical help, after first being sent to a psychiatric hospital. She had also started to have “peculiar bodily feelings,” like “tingling in the left side of her face, a feeling of floating in the air looking down on her body, and a feeling of compulsion to do things.”

When she was examined, they found that she had had epilepsy when she was younger. Through EEG they noticed abnormal activity in the right side of her brain and diagnosed her with nonconvulsive status epilepticus, or epilepsy without seizures. After being treated for her epilepsy, the déjà vu went away. “Shona was greatly delighted to find the world restored to its only roughly familiar, obligingly unpredictable old self,” Zeman writes.

When she recovered from her déjà vu, though, she could no longer recognize faces, a condition called prosopagnosia. Zeman says they found a vascular abnormality in the part of the brain where facial recognition takes place. That abnormality had initially manifested as déjà vu before emerging as prosopagnosia. When Zeman met her in 2000, she couldn’t recognize famous people on TV and her relatives had to introduce themselves by name each time they came to see her.

Moulin cautions that sometimes people use the phrase déjà vécu to describe patients that have memory delusions, the confabulation that everything is repeating—like his first patient. But in déjà vécu, self-awareness is key. In fact, Zeman’s first patient, the one who wanted her loud popping noise to go away, was an apt example of déjà vécu—hers was a stronger, more persistent experience than déjà vu. But she didn’t actually believe her life was repeating, or that they were actual memories she was retrieving. She didn’t come up with stories to explain what was happening. “It felt to her very much like an illusion and a strange sensation,” Moulin says.

There may be a need for even greater refinement of the many déjà-like experiences, to separate them out, especially if they have different underlying mechanisms. (There’s even a phenomenon now, considered separate, known as déjà-rêvé, which is an intense recollection of one’s dreams. It too has been shown to be provoked through electrical stimulation in the brains of epileptics, and has been reported by people with epilepsy during seizures.)

I am a person who gets déjà vu regularly. Not enough to qualify as persistent, but I think more than most. I ask Moulin what he thinks this means. Has my in-brain fact checker had too many cups of coffee? Is my brain really good at noticing even the slightest errors in over-familiarity?

Moulin says that people with déjà vu could be more in touch with the signals being given off by their cognitive systems, or especially sensitive to how their familiarity systems are working. But Moulin says we don’t know why some people get it more than others. He says he’s met extremely bright people who have never experienced it, so unfortunately for me it’s not necessarily a mark of intelligence or an exceptional brain.

He does wonder if people who don’t get déjà vu have the same relationship with their memory than those who have it a lot. “People who experience déjà vu might use more of their reflective abilities to think about what’s going on in their memory system,” he says. “Maybe they have this sort of memory they don’t trust all the time. Whereas people who don’t have déjà vu, they just explain everything away once they find something familiar. They try and find a reason for why they find it familiar and they don’t enjoy the same mysterious relationship with their own memory.”

Moulin says that he used to have déjà vu more than most, even before he started his research. “I think that’s quite consistent with how I was always interested with how things were working,” he says. “You can’t really create déjà vu, but you can cultivate the way of thinking about what you’re thinking about. That might make you a bit more likely to notice it than other people.”

Moulin asks me if I remember my first time experiencing déjà vu, saying that in most people, it starts around the age of ten, but not earlier. “I remember my first. I don’t know if you remember your first,” he says.

I do remember my first—I was nine or ten and on the playground at my elementary school. I never forgot it because it was so powerful and strange. It’s also odd to remember it—a real memory of a feeling of false familiarity.

“Yeah, then you get into all kinds of recursive Donnie Darko kind of loops,” Moulin laughs. But the fact that déjà vu doesn’t happen commonly at much younger ages supports the “fact-checker” theory that Moulin holds. “Before that age we don’t have those reflective capacities,” he says. “We haven’t learned yet to mistrust or evaluate our memory system and we don’t really coordinate and think about our memory in the same way that we do as adults.”

And for people who have never had it, it’s a hard thing to explain. It’s a powerful feeling, but subjective, one of the many challenges that comes with studying it—even if it can reveal the intricacies and mechanisms of memory, recollection, and familiarity in potentially new ways. Moulin says that he’s met researchers or academics who have never experienced it themselves, and can’t be sure it exists.

“To them,” he says, “I might as well be researching ghosts.”

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Why do I have déjà vu all the time?

Because you are not suppressing your higher intelligence with illusory ego games.

When I was young I had deja vu all the time. There was an incident when I was 12 or so, I fell and injured myself and the next 5 minutes replayed like a movie out of recurring dreams I’d had for years. Or so it seems. Isn’t it weird that we don’t really remember having the dreams but deja vu seems like it must have been from a dream?

They continued frequently into my mid 20s, when I had a “brilliant” idea: what if I can change what happens in the midst of a deja vu?

DO NOT DO THIS. Yes it can be done. The results are devastating. Promise me you won’t do it. Please.

I truly believe this experiment destroyed the life I could have lived. The deja vu completely stopped in only a few tries. It took several years before the damage became apparent. Once it was, there was no backing out, I was headed for complete disaster.

Because my ego got the better of me. I thought if I was powerful enough to shift the course of destiny, I could really achieve something important. I could not have been more wrong.

If there is a God, and It has a plan, how would you know what the plan is? Is there a map somewhere in your mind that lays out the path? How would you recognize that map amidst all the other noise in your head?

If you don’t like the “because God” or “because destiny” arguments, consider this:

We live in a deterministic universe that is bound to increase in entropy over time. We have enormous processing potential within our minds.

Why couldn’t deja vu occur from pure logical processing in a suitably complex mind? If you “know” the deterministic rules, it is certainly possible to predict the future. Not likely, but possible. If you can minimize the impact of entropy, you are more likely to do so.

So, if there is a “right path” to follow in life, it is our responsibility to minimize entropy, and the mind can work out the rest in minute detail.

Ego introduces entropy to the equation of life. If you can follow the math without invoking ego, you should be able to see things clearly.

Deja vu is a superpower. It will bring you an amazing, authentic, and meaningful life, so long as you stay humble about it.

Spirituality and The Brain

One reason psychologists get the diagnosis wrong so often is that TLE isn’t listed in the DSM-IV, the Diagnostic and Statistical Manual of Psychological Disorders, the psychiatrist’s handbook. It’s the standard guide to diagnosing psychiatric illness. Because it isn’t listed, its pathology isn’t covered, and psychologists miss the mark when dealing with it. TLE also has a much wider range of possible symptoms than other disorders. While most seizures of this type (called complex partial seizures) begin in the amygdala, they spread into other structures, and there are quite a number of them. One nearby structure will introduce smells into the experiences, and leave someone a heightened sense of smell. Another will create distortions in spatial perception. Another can leave someone with overactive sweat glands. Another can leave someone wanting to talk or write all the time. Another can make a person prone to brief, intense bursts of anger. Another can make a person’s sexuality change. The list goes on. There are also a variety of personality changes that can happen. With so many possible symptoms, proper diagnosis can be a problem.

There’s no need for a diagnosis when Déjà Vu feels good, even if it’s TLE that’s emotionally positive. In that case, it really can’t be called a disorder, but people still feel that it somehow calls for a response, and it will ‘feel’ like it should be a spiritual one.

For Déjà Vu that feels spiritual, I suggest meditation. The kind that emphasizes being present in the here and now. Déjà Vu is an alteration in the perception of the present moment. The two best known ones are Zen and vipassana, both Buddhist practices. I’m not saying that people who have Déjà Vu a lot should become Buddhists, only that these two Buddhist practices are well suited for those with frequent Déjà Vu experiences. There are times I’ve thought that Jesus might have been close to these practices when he said to ‘be still and know”. The more often Déjà Vu happens, the more likely a person will be able to stop their ongoing mental processes, and just be in the present. Déjà Vu is an experience that won’t go into words very well. When its happening, a person can still speak, but the phenomena that will demand their attention is that sense of the past.

Most commonly, a person having Déjà Vu will give their attention to the feeling that ‘this is the past!’ If someone wants to use the experience to enhance their spirituality, there are three things they can try.

1) When Déjà Vu happens, you should focus on what’s happening in the present. You can pay attention to your senses, and look at the ‘sense’ that perceives that sense of familiarity. If you can get a clear perception of that ‘sense’, you can look there at any time. Especially while practicing meditation. This practice, for those who have Déjà Vu often enough to take advantage of it, can chop months off the time it takes to get into meditation deeply.

2) You should try to disconnect from your sense of the past and try to see the present through that same sense.

3) You can pretend that Déjà Vu is happening during meditation. With practice, the familiar sensation should eventually appear, and by then, you may be able to stop paying attention to the ‘past’ and go into being ‘present’. When this happens, your meditation practice should acquire something new. This one may be hard to do, so let it go if it doesn’t work for you.

With time, Déjà Vu can become a friend.


Watch my video about Deja Vu.
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How do you personally relate Déjà Vu to the existence of time?


These are provisional opinions only, something like ‘working hypotheses’, but to me, time is a matter of subjective experience which follows as-yet undiscovered algorithms. A year is a long time when you’re nine years old, and much shorter when you’re 40.

Déjà Vu and the phenomena of time are completely unrelated, despite the connection we feel between them. Understanding one offers no clues to the other. We may understand the physics of time and the time-space continuum, but the sense of the past is a feeling, and our feelings don’t match the laws of physics.

Déjà Vu is ‘about’ the past. There is a related phenomenon – ‘future memory’, whose existence offers the possibility that Déjà Vu and ‘future memory’ are at two different ends of a single spectrum. If so, then we have perception in two directions – past and future.

A skeptical scientist would deny the existence of future memory, and there is no evidence that can prove them wrong. I have yet to experience the phenomena myself, and I have no ongoing jobs right now that would change if I held an opinion on the subject, so I prefer not to decide about it now.

Time only runs in one direction.

My opinion is that Déjà Vu is a neural phenomenon, and not connected to time (“The time-space continuum”) itself. It’s a change in our perception of time. Relating it to time itself is a bit like saying that sunlight wavers when it hits water instead of seeing that the water has waves.

It may or may not reference actual events in the past. The sense of the past is enough to create the feeling.

It may also be that there are two mechanisms – one behind Déjà Vu ‘to’ actual events, and one that spins out (confabulates) memories to which the Déjà Vu seems to refer.

For the mind to create a memory, right in the moment, that matches the present is a small thing next to the entire worlds it can create in dreams, visions, and near-death experiences.


(2) Gloor, Pierre, MD, Ph.D., Et Al, “The Role of the Limbic System in Experiential Phenomena of Temporal Lobe Epilepsy” Annals of Neurology Vol. 12, No.2 August 1982

(3) Persinger, M.A., “Geophysical Variables and Behavior: XXII. The Tectonic Strain Continuum of Unusual events” Perceptual and Motor Skills 1985, 60, 59-65

(4) Persinger, M.A. & Lafreniere, “Space-time Transients and Unusual Events” Nelson-Hall Chicago, 1977

Also Read “Future Memory” by PMH Atwater.

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Glasses For Enhanced Visual Acuity
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What Caused The Big Bang?

Have you ever experienced a sudden feeling of familiarity while in a completely new place? Or the feeling you’ve had the exact same conversation with someone before?

This feeling of familiarity is, of course, known as déjà vu (a French term meaning “already seen”) and it’s reported to occur on an occasional basis in 60-80% of people. It’s an experience that’s almost always fleeting and it occurs at random.

So what is responsible for these feelings of familiarity?

Despite coverage in popular culture, experiences of déjà vu are poorly understood in scientific terms. Déjà vu occurs briefly, without warning and has no physical manifestations other than the announcement: “I just had déjà vu!”

Many researchers propose that the phenomenon is a memory-based experience and assume the memory centres of the brain are responsible for it.

Memory systems

The medial temporal lobes are vital for the retention of long-term memories of events and facts. Certain regions of the medial temporal lobes are important in the detection of familiarity, or recognition, as opposed to the detailed recollection of specific events.

It has been proposed that familiarity detection depends on rhinal cortex function, whereas detailed recollection is linked to the hippocampus.

The randomness of déjà vu experiences in healthy individuals makes it difficult to study in an empirical manner. Any such research is reliant on self-reporting from the people involved.

Glitches in the matrix

A subset of epilepsy patients consistently experience déjà vu at the onset of a seizure – that is, when seizures begin in the medial temporal lobe. This has given researchers a more experimentally controlled way of studying déjà vu.

Epileptic seizures are evoked by alterations in electrical activity in neurons within focal regions of the brain. This dysfunctional neuronal activity can spread across the whole brain like the shock waves generated from an earthquake. The brain regions in which this electrical activation can occur include the medial temporal lobes.

Electrical disturbance of this neural system generates an aura (a warning of sorts) of déjà vu prior to the epileptic event.

By measuring neuronal discharges in the brains of these patients, scientists have been able to identify the regions of the brain where déjà vu signals begin.

It has been found that déjà vu is more readily induced in epilepsy patients through electrical stimulation of the rhinal cortices as opposed to the hippocampus. These observations led to the speculation that déjà vu is caused by a dysfunctional electrical discharge in the brain.

These neuronal discharges can occur in a non-pathological manner in people without epilepsy. An example of this is a hyponogogic jerk, the involuntary twitch that can occur just as you are falling asleep.

It has been proposed that déjà vu could be triggered by a similar neurological discharge, resulting in a strange sense of familiarity.

Some researchers argue that the type of déjà vu experienced by temporal lobe epilepsy patients is different from typical déjà vu.

The déjà vu experienced prior to an epileptic seizure may be enduring, rather than a fleeting feeling in those who don’t have epileptic seizures. In people without epilepsy the vivid recognition combined with the knowledge that the environment is truly novel intrinsically underpins the experience of déjà vu.

Mismatches and short circuits

Déjà vu in healthy participants is reported as a memory error which may expose the nature of the memory system. Some researchers speculate that déjà vu occurs due to a discrepancy in memory systems leading to the inappropriate generation of a detailed memory from a new sensory experience.

That is, information bypasses short-term memory and instead reaches long-term memory.

This implies déjà vu is evoked by a mismatch between the sensory input and memory-recalling output. This explains why a new experience can feel familiar, but not as tangible as a fully recalled memory.

Other theories suggest activation of the rhinal neural system, involved in the detection of familiarity, occurs without activation of the recollection system within the hippocampus. This leads to the feeling of recognition without specific details.

Related to this theory, it was proposed that déjà vu is a reaction of the brain’s memory systems to a familiar experience. This experience is known to be novel, but has many recognisable elements, albeit in a slightly different setting. An example? Being in a bar or restaurant in a foreign country that has the same layout as one you go to regularly at home.

Even more theories exist regarding the cause of déjà vu. These span from the paranormal – past lives, alien abduction and precognitive dreams – to memories formed from experiences that are not first-hand (such as scenes in movies).

So far there is no simple explanation as to why déjà vu occurs, but advances in neuroimaging techniques may aid our understanding of memory and the tricks our minds seem to play on us.

Can déjà vu tell us what’s coming next?

Have you ever had that strange feeling of passing a person and just knowing you’ve seen them before? Perhaps you even think that you know what might happen in the next moment. This odd sensation is known as “déjà vu” (“already seen”). But why does it occur?

Share on PinterestResearchers are striving to untangle the mystery of déjà vu and related experiences.

Years ago, as a freshman in college, I sat down to watch an animated series with my friends of an evening. The moment that the first episode started, I had this strong, uncanny feeling that I’d seen it all before.

Yet I knew beyond a doubt that this was my first viewing, and I had never heard of that show before my friends pointed it out to me.

What I experienced then was something that, at least anecdotally, many people experience at some point in their lifetime: déjà vu, or the mysterious feeling that something new is unexpectedly familiar.

Few researchers have taken much interest in this phenomenon, but Anne Cleary — from Colorado State University in Fort Collins — is one who has.

She has been paying special attention to the brain mechanics of this experience for a few years now, and recently she has extended her project to answering the question: does the feeling of premonition often associated with déjà vu have a real basis?

The results of this study — which Cleary co-led with former graduate student Alexander Claxton — have now been published in the journal Psychological Science.

A phenomenon of frustrated recall

In their new research, Cleary and Claxton induced the experience of déjà vu in study participants in order to test the co-occurrence of premonitory feelings and to see whether such feelings were consistent with the actual situation.

In other words, the researchers wanted to see whether people who had had a déjà vu experience could really predict what was coming next, or whether that sensation was just a trick of the mind.

To induce déjà vu, Cleary used a strategy that she had successfully tested in a previous study.

In 2012, she argued that the feeling of having “already seen” is a memory-related phenomenon, akin to the sensation of words that elude us — much like when we have a word “on the tip of our tongue,” as it were, yet try as we might we cannot recall it, despite the fact that we know we know it.

Cleary discovered that when we experience déjà vu, it could be because the context reminds us of something we’ve already seen or experienced in real life but which we can no longer properly remember.

Thus, we may have the feeling that we’ve already been to an utterly new place if, say, it reminds us of a place once glimpsed from a train but which we’re no longer conscious of ever having seen.

“We cannot consciously remember the prior scene, but our brains recognize the similarity,” explains Cleary. “That information comes through as the unsettling feeling that we’ve been there before, but we can’t pin down when or why.”

Both déjà vu and the “tip of the tongue” feeling are known as “metamemory” phenomena: when we know that we remember, or that we ought to remember, something.

“My working hypothesis is that déjà vu is a particular manifestation of familiarity. You have familiarity in a situation when you feel you shouldn’t have it, and that’s why it’s so jarring, so striking.”

Anne Cleary

Déjà vu and premonitions

In their recent study, Cleary and Claxton made the participants experience déjà vu by asking them to explore 3-D virtual landscapes.

The strategy was simple: landscapes were mapped in identical fashion yet they looked completely different — for example, sometimes participants would see junkyard scene, while at other times they were shown a hedge garden.

In each case, “ovement through the scene stopped before a critical turn.” Therefore, all of the participants felt like they had already seen a particular landscape because they had — but in a completely different form.

Then, the researchers tested whether participants with déjà vu who thought they could predict the next turn would actually be able to do so correctly, or whether they were just being duped by their brains.

Such a trick of the mind, Cleary explains, would be explained by a particular theory of memory, which argues that we store memories so we can learn to “predict” future situations. This could allow us to ensure that we survive and thrive.

The researchers saw that approximately half of the participants who reported déjà vu also said that they had premonitory sensations. But “the probability of choosing the correct turn during déjà vu” was no stronger than the probability of picking a wrong direction.

In short, while we may think that we can predict what’s going to happen next in an experience of déjà vu, that impression remains ungrounded in reality.

Now, Cleary is leading follow-up experiments focused on the feeling that “you just know what’s meant to happen next.”

In doing so, she hopes to gain a better understanding of what causes this feeling, and whether it’s really related to the sensation of familiarity.

The percentage of people who experience déjà vu is probably somewhere between 30% (about 8 in a class of 30) and 100% (everyone in a class of 30) . We are not sure about the exact percentage for two important reasons. First, we cannot ask everyone in the world so we have to use the results of surveys of small groups of people. This is a problem because surveys can give us quite different results depending on who we ask. Second, people can give very different answers depending on the definition we give of déjà vu. Asking the question in different ways can get very different results.

We can also get an idea of how often déjà vu happens by asking people. Again, the answers they give depend on who they are and how we ask them the question, but most people report déjà vu somewhere between every few weeks and every few months. Typically, this means that déjà vu is not very common so if you have experienced it recently you are very lucky!

Why Do Some People Get Déjà Vu More Often Than Others?

Source: Alexander Image/

Many of you know the feeling: You’ll be going about your day, minding your own business, folding some laundry—nothing out of the ordinary—when suddenly a sensation of familiarity washes over you, and you’re completely aware that it’s happening: I’ve been here before.

Except you haven’t. Or have you?

You might try to think back and pinpoint when you’d experienced this moment before. But just as quickly as the feeling hits you, it’s gone.
Did you predict the future? Were you seeing something from a past life? What is déjà vu, anyway?
The phenomenon of déjà vu (French for “already seen”) is pretty poorly understood from a scientific perspective, but there are a few theories:

  • Déjà vu may be the result of some sort of “mismatch” in how we’re simultaneously sensing and perceiving the world around us. Perhaps we smell something familiar, for example, and our mind is instantly transported to the first time we smelled it. (It’s a vague theory, though, and doesn’t explain why most déjà vu episodes don’t reflect true past events.)
  • Déjà vu may be a fleeting malfunctioning between the long- and short-term circuits in the brain. The information our brain takes in about its surroundings may “shortcut” its way straight to long-term memory, bypassing typical storage transfer mechanisms, so when we have a moment of déjà vu, it feels as though we’re experiencing something from our distant past.
  • A region of the brain called the rhinal cortex, involved in detecting familiarity, may be inexplicably activated without actually activating memory (hippocampal) circuits. That may explain why déjà vu episodes feel so non-specific when we try to figure out where and when we had previously experienced a particular moment. In fact, some patients with epilepsy reliably experience déjà vu at the beginning of a seizure. For these individuals, experimental stimulation of the rhinal cortex — and not so much the hippocampus itself — induces déjà vu.

Source: University of Bristol

Déjà vu is estimated to occur in 60-70% of people, most commonly in those between the ages of 15 and 25. Why? We have no idea. Interestingly, though, I had previously written about déjà vu years ago out of my own curiosity on the matter, having experienced it fairly frequently. I’m now 26, though, and can’t remember the last time I had an episode.
Are any of these theories correct? We may never know. After all, since episodes of déjà vu are completely unexpected—not to mention extremely rare for most of us—empirical research on the topic is next to impossible.

What are your experiences with déjà vu?

caption It’s one of the oddest sensations. source ian dooley / Unsplash

  • About 70% of the population experience déjà vu.
  • It’s the sense of familiarity that feels misplaced because you know you haven’t experienced the same thing before.
  • Psychologists and neuroscientists have come up with several different theories over the years for why we experience the strange sensation.

It’s one of the oddest sensations. That feeling where you are in a new situation, or a completely new environment, but you get an intense feeling of familiarity. For no apparent reason, you feel like you’re reliving a past experience.

It’s called déjà vu, which is French for “already seen,” and it happens to an estimated 70% of the population, according to How Stuff Works, with people aged between 15 and 25 years old experiencing it most.

Unless it’s happened to you, it’s a hard experience to explain, but it’s a bit like trying to remember a dream that is slipping away. And as soon as you rack your brain to try and think back to when you might have experienced something familiar, the feeling is gone.

Déjà vu is difficult to study as it is so fleeting. It has puzzled researchers as to how to replicate it in a laboratory environment. This has led to a few different theories over time about how and why our brains act this strange way.

Accidental triggers in the brain

Back in 2006, scientists at the Leeds Memory Group thought they had gone some way to recreating the sensation in a lab by using hypnosis to trigger part of the brain’s recognition process. The experiment was based on the theory that two key processes happen in the brain when we recognise something or someone familiar.

Firstly, our brains search through our memories to see if we’ve observed the scene before, and if it comes up with a match, a separate area of the brain identifies it as familiar. In déjà vu, the second part of the process could be triggered by accident.

The researchers recruited 18 volunteers, who were asked to look at 24 common words. Then they were hypnotised and told that when they were presented with a word in a red frame, it would feel familiar. Words in green frames would make them think the word was in the original list of 24.

After being taken out of hypnosis, the subjects were given a series of words in different coloured frames, including some words that didn’t appear in the original list. In the group, 10 said they felt a peculiar sensation when they saw new words in red frames, and 5 said it felt like they were having déjà vu.

Malfunctioning memory

Over the years, psychologists have come up with a few different theories for déjà vu.

It could be some sort of malfunctioning between the long and short term circuits in the brain, meaning new information may take a shortcut straight to long-term memory. This skips over the mechanisms the brain normally uses to store information, so it could feel like we are experiencing something from the past.

It could also be something to do with the rhinal cortex, which is an area of the brain that makes us feel familiarity. It could somehow be activated without triggering other areas associated with memory. That could explain why it’s so difficult to pin down what feels familiar about the déjà vu. It’s usually a vague familiarity, not a specific object or person.

A fourth theory is that the feeling déjà vu is set off by false memories. Psychologist Valerie F. Reyna came up with one of the leading theories for false memories. She told Business Insider:

“ is certainly related to false memory in the sense that it is a memory dissociation kind of effect. It dissociates reality from your memory.

“There’s all kinds of different dissociative experiences that can happen. Sometimes you cannot be sure, for example, if you dreamed something or experienced it, if you saw it in a movie or it happened in real life.”

It’s most likely a memory mismatch

Work last year by psychology researcher Akira O’Connor, however, suggested false memories may not be to blame. Instead, it could be a sign of the brain checking its memory.

O’Connor and his team scanned the brains of 21 volunteers while doing a common test for triggering false memories, New Scientist reported.

To do this, you give a person a list of related words, such as bed, night, snooze, and nap. Then, when the person is asked about the words afterwards, they tend to give words related to what they’ve heard – in this case it would be “sleep.”

To try and create the feeling of déjà vu, the researchers asked the subjects if they heard any words beginning with “s,” which they replied they hadn’t. But when they asked about the word “sleep,” they were able to remember they couldn’t have heard it, but it felt familiar all the same.

The team expected to see areas of the brain associated with memory – such as the hippocampus – light up. But it didn’t. Instead, areas involved in decision making were active.

When presenting the findings at the International Conference on Memory in Budapest, O’Connor said he thinks the frontal regions of the brain could be flipping through our memories, then sending signals if there’s a mismatch between what we think we’ve experienced and what we actually have experienced.

“Brain regions associated with memory conflict, rather than false memory, appear to be driving the déjà vu experience,” O’Connor wrote in a blog post about the findings.

“This is consistent with our idea of déjà vu as the conscious awareness of a discrepancy in memory signals being corrected. This, in turn, sheds some light on why déjà vu occurrence appears to decline with age despite the fact that memory errors tend to increase with age. If it’s not an error, but the prevention of an error, this makes a lot more sense.”

3 Reasons You Sometimes Have Déjà Vu, According to Science

Getty Images

You know that feeling you get when you step inside a new house or walk around a foreign city—places you know you’ve never been before—and you can’t help but think, I’ve done this already? It’s déjà vu, and if you’ve never had it before, take it from us: It’s kind of creepy.

Déjà vu is French for “already seen,” and about two out of three people have experienced the phenomenon at one time or another, according to a 2003 review in the journal Psychological Bulletin. Despite being fairly common, “it’s not a widely studied subject,” says Alice Medalia, PhD, a professor of medical psychology at Columbia University Medical Center. And because déjà vu is a subjective experience—in other words, it’s difficult to induce in research subjects—testing the theories behind it can be tricky.

That said, researchers have a few guesses about why we experience déjà vu (and no, it’s probably not flashbacks to a previous life):

You’ve been somewhere similar before

Some researchers believe déjà vu is triggered when you enter an environment similar to one you’ve experienced in the past. For example, you could experience it when you enter a hotel lobby where the furniture is configured the same way as your childhood home’s living room.

RELATED: 17 Ways to Age-Proof Your Brain

Researchers tested that theory in a 2009 study published in the journal Psychonomic Bulletin & Review. They showed volunteers images that had nothing to do with one another—a fenced-in courtyard, and then later, a locker room—and the volunteers felt déjà vu because the images were composed in a very similar way. The researchers concluded that there was probably a connection between déjà vu and the feelings of “familiarity.”

You travel a lot

People who travel and people who can recall their dreams are more likely to experience déjà vu than those who stay at home or don’t remember their dreams, according to the 2003 review. These people can draw on a wider range of sources (either from, say, their adventures Europe, or just their own imagination), so it makes sense that they should think other environments feel familiar, too.

Something’s up with your brain

Some people who have temporal lobe epilepsy (a type of epilepsy that occurs in the part of your brain that handles short-term memory) experience déjà vu right before they have a seizure—another sign that the phenomenon may be connected with the way memories are activated. Plus, it’s why some experts think déjà vu is triggered by a kind of disruption in the firing of neurons in the brain, says Dr. Medalia.

It could also be the result of your brain struggling to process multiple pieces of information, but for some reason, can’t align them correctly, she says. That lack of “synchrony,” in med-speak, might be responsible for that déjà vu feeling.

RELATED: 21 Reasons You’ll Live Longer Than Your Friends

The bottom line?

Regardless of what’s happening (or what’s causing it), for the vast majority of people, déjà vu is pretty harmless. Unless you’re experiencing an epileptic seizure—and in that case, there are plenty of other signs to watch out for—it’s a relatively normal experience.

And you never know—maybe that castle in London looks so familiar because, in your past life, you were Kate Middleton’s great-great-great-great grandmother-in-law. Hey, we can dream, right?

Dear Lifehacker,
I’ve been experiencing déja vu more often lately—you know, that odd feeling where you can swear you’ve been somewhere before or had the same conversation with someone but really didn’t. Is this bad? Should I be concerned? My friend says she used to get it a lot but hasn’t for years. Should she be concerned? Is this just a glitch in the Matrix?

Seeing Glitches

Dear S.G.,
Déjà vu really is an uncanny feeling. The term in French literally means “already seen” and that’s exactly why it’s so unnerving: It really feels like you’ve already experienced a very specific event or been somewhere, even though you haven’t (or, at least, you don’t think so).


Further complicating the matter, there’s no consensus yet on what exactly causes this phenomenon, though there are a lot of theories. Psychology Today points out a study that suggests that déjà vu is just an extreme reaction of your brain’s memory system when encountering things with lots of familiar objects just set up a little differently (for example, when you’re in a restaurant configured almost identically to one you’ve been in before, you can get a powerful feeling of familiarity).

Scientists have found a possible cause for déjà vu occurences in the brain. Popsci reports that mice lacking some specific receptors in the hippocampus area of the brain have responses similar to déjà vu, so the theory is that déjà vu can be just a temporary disorientation in the hippocampus, which is the part of the brain responsible for sense of direction and forming new memories.

To answer your questions, though, déjà vu appears to be harmless for most people (as much as 70 percent of the population has reported experiencing it, according to Discovery’s How Stuff Works), with higher rates of occurence in people age 15 to 25—so your friend’s decreased déjà vu experiences should be fine, too.

However… déjà vu has also been associated with temporal-lobe epilepsy (one story shows a woman who had twenty years of déjà vu episodes before finding out she had epilepsy). So, not to alarm you, but if you experience frequent déjà vu, you may want to see a doctor.


Finally, have you been feeling anxious or stressed out lately? Wikipedia mentions a link between déjà vu and anxiety, and you’ll find lots of stressed out people on health forums who also say they’ve been experiencing more déjà vu. So our Lifehacker tip for trying to stop déjà vu from happening, if you want to, is good old stress and anxiety reduction.


Photo remixed from an original by istolethetv.

You can follow or contact Melanie Pinola, the author of this post, on Twitter or Google+.


How Déjà Vu Works

Have you ever visited ­a store for the first time and had it feel eerily familiar? Or maybe you’re deep in conversation with a friend and you suddenly get the feeling that you’ve had the exact conversation before, even though you know that you haven’t. If you’ve ever found yourself in either of these situations, you’ve experienced déjà vu. Sixty to 70 percent of us admit to getting this feeling at least once in our lives. The sight, sound, taste or even smell of something makes us think that we’ve experienced it before, although we know that we couldn’t have.

There are more than 40 theories as to what déjà vu is and what causes it, and they range from reincarnation to glitches in our memory processes. In this article, we’ll explore a few of those theories to shed some light on this little understood phenomenon.


Déjà vu is a French term that literally means “already seen” and has several variations, including déjà vécu, already experienced; déjà senti, already thought; and déjà visité, already visited. French scientist Emile Boirac, one of the first to study this strange phenomenon, gave the subject its name in 1876.

There are often references to déjà vu that aren’t true déjà vu. Researchers have their own definitions, but generally déjà vu is described as the feeling that you’ve seen or experienced something before when you know you haven’t. The most common misuse of the term déjà vu seems to be with precognitive experiences — experiences where someone gets a feeling that they know exactly what’s going to happen next, and it does. An important distinction is that déjà vu is experienced during an event, not before. Precognitive experiences — if they are real — show things that will happen in the future, not things that you’ve already experienced. (However, one theory about déjà vu deals with precognitive dreams that give us a “déjà vu feeling” afterwards. See the Déjà Vu and Precognitive Dreams section.)

Hallucinations that are brought on by illness or drugs sometimes bring a heightened awareness and are confused with déjà vu. False memories that are brought on by schizophrenia can be confused with déjà vu as well. Unlike true déjà vu, which typically lasts from 10 to 30 seconds, these false memories or hallucinations can last much longer.

What Exactly Is Happening In Your Brain When You Get Déjà Vu?

Even had that dizzying feeling that you’ve been somewhere before, not just somewhere, but in that exact spot, doing the exact same thing, with the same people-even though you know there’s no way that could be true?

Déjà vu, that sometimes magical, sometimes disconcerting feeling of already having lived the present moment, has been part of the human experience forever. We’ve explained it as a futuristic vision, a glimpse into a former life, a warning from beyond or some other kind of mystical experience. But now science has a biological explanation: It’s a brain glitch. Sorry.

Researchers from Texas A&M University were researching epilepsy, a disease that causes repeated seizures, and found something interesting: Epileptics often have a moment of déjà vu right before a seizure hits, almost like an early warning system. The scientists used brain scans to examine the link between déjà vu and seizures and they found that both events appear to be caused by the same neurological hiccup in our brains. (Did you know leg workouts could be key to better brain health?)

But déjà vu is super common, with over two-thirds of people saying they’ve experienced it, while epilepsy is relatively rare, affecting just one percent of the population. So how exactly are they connected? It all comes down to how we store our memories, lead researcher Michelle Hook, Ph.D., an assistant professor in the Department of Neuroscience and Experimental Therapeutics, said in a press release. The temporal lobe is where the nerve cell activity in the brain is disrupted in patients with temporal lobe epilepsy, and it’s also the place where we make and store our memories. (Find out how technology messes with your memory.)

Hook explained that this part of our brain is responsible for the detection of familiarity and the recognition of certain events, so when there is a neurological misfire there, it can lead us to mistake the present for the past. For people with epilepsy, the neurological disruption continues on to cause a full-blown seizure, but in healthy patients, it just causes that all-too-familiar feeling of déjà vu.

Another factor, according to the study, is that our brains are constantly trying to create a whole picture of the world based on our limited sensory input. They do this by filling in the gaps with what we know from past experience-for instance, a honking horn tells us there’s a car and there’s danger, even if we can’t see it. Most of the time this works seamlessly, but every once in awhile our brains fill in the blank with the wrong piece of information, leading to a strange “memory” happening in the present moment. (Stock up on the 11 Best Foods for Brain Health.)

Lastly, the different speeds at which we process all that incoming sensory data may also spark déjà vu. For instance, we may process what we see slightly before we process what we hear and that difference may make us think we’re having two experiences at the same time.

“Some suggest that when a difference in processing occurs along these pathways, the perception is disrupted and is experienced as two separate messages. The brain interprets the second version, through the slowed secondary pathway, as a separate perceptual experience, and thus the inappropriate feeling of familiarity (déjà vu) occurs,” Hook explained.

So now that we know why it happens, the real question is if déjà vu moments are basically just pre-seizures does that mean The Matrix is a true story after all??

  • By Charlotte Hilton Andersen @CharlotteGFE

By Jessica Hamzelou

Looks familiar…

Daniel Högberg/plainpicture

Feel like you’ve read this before? Most of us have experienced the eerie familiarity of déjà vu, and now the first brain scans of this phenomenon have revealed why – it’s a sign of our brain checking its memory.

Déjà vu was thought to be caused by the brain making false memories, but research by Akira O’Connor at the University of St Andrews, UK, and his team now suggests this is wrong. Exactly how déjà vu works has long been a mystery, partly because its fleeting and unpredictable nature makes it difficult to study. To get around this, O’Connor and his colleagues developed a way to trigger the sensation of déjà vu in the lab.

Master your memory

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The team’s technique uses a standard method to trigger false memories. It involves telling a person a list of related words – such as bed, pillow, night, dream – but not the key word linking them together, in this case, sleep. When the person is later quizzed on the words they’ve heard, they tend to believe they have also heard “sleep” – a false memory.

To create the feeling of déjà vu, O’ Connor’s team first asked people if they had heard any words beginning with the letter “s”. The volunteers replied that they hadn’t. This meant that when they were later asked if they had heard the word sleep, they were able to remember that they couldn’t have, but at the same time, the word felt familiar. “They report having this strange experience of déjà vu,” says O’Connor.

Brain conflict

His team used fMRI to scan the brains of 21 volunteers while they experienced this triggered déjà vu. We might expect that areas of the brain involved in memories, such as the hippocampus, would be active during this phenomenon, but this wasn’t the case. O’Connor’s team found that the frontal areas of the brain that are involved in decision making were active instead.

What goes on inside your head? More about memory and how to flex your mental muscle

O’Connor presented these findings at the International Conference on Memory in Budapest, Hungary, last month. He thinks that the frontal regions of the brain are probably checking through our memories, and sending signals if there’s some kind of memory error – a conflict between what we’ve actually experienced and what we think we’ve experienced.

“It suggests there may be some conflict resolution going on in the brain during déjà vu,” says Stefan Köhler at the University of Western Ontario in Canada.

A healthy head

If these findings are confirmed, they suggest that déjà vu is a sign that your brain’s memory checking system is working well, and that you’re less likely to misremember events.

This would fit with what we already know about the effects of age on memory – déjà vu is more common in younger people and trails off in old age, as memory deteriorates. “It may be that the general checking system is in decline, that you’re less likely to spot memory mistakes,” says O’Connor.

Christopher Moulin at Pierre Mendès-France University in Grenoble says the findings do not bode well for people who don’t experience déjà vu at all. “Without being unkind, they don’t reflect on their memory systems,” he says.

But people who don’t experience déjà vu might just have better memory systems in the first place, says O’Connor. If they’re not making memory errors, there’s no trigger for déjà vu, he says.

We still don’t know if déjà vu is beneficial, says Köhler. “It could be that déjà vu experiences make people cautious, because they might not trust their memory as much,” he says. “But we don’t have any evidence for that yet.”

More on these topics:

  • brains
  • neurology
  • memory

Scientists May Have Finally Explained Déjà Vu

Researchers have a new explanation for one of the brain’s most uncanny peculiarities – the phenomenon of déjà vu. Presenting his team’s latest work at the recent International Conference on Memory in Budapest, Akira O’Connor from the University of St Andrews described how apparent glitches in the Matrix may in fact just be the brain fact-checking its own memory system.

According to New Scientist, O’Connor and his colleagues began by devising a technique to artificially trigger déjà vu. To achieve this, they presented study participants with a series of connected words, without revealing the one word that links them. For instance, in one trial the words bed, pillow, dream and night were all presented, yet the term sleep – which clearly connects all of these words – was omitted.

To make sure participants registered that they hadn’t heard the word sleep, the researchers asked them whether or not they had heard any words beginning with an “S”, to which they obviously replied in the negative. However, when they were later grilled on which words had been presented, most tended to think they could remember hearing the word sleep, despite knowing that they hadn’t, resulting in an eerie sense of déjà vu.

Using functional magnetic resonance imaging (fMRI), the team observed that when this occurred, the most active regions of participants’ brains were not those normally associated with memory, such as the hippocampus. Instead, the frontal areas, which are typically involved in decision making, were activated during the déjà vu experience.

As such, O’Connor believes that these frontal regions probably monitor our memories as they are replayed, looking for errors in their content and becoming activated when they spot an irregularity. As Stefan Köhler from the University of Western Ontario told New Scientist: “There may be some conflict resolution going on in the brain during déjà vu.”

Though more work is needed in order to validate this theory, if correct it would suggest that the brain engages in quality control, monitoring its own activities and flagging up any errors that might occur. In this context, the frontal areas seem to be checking for inconsistencies between what we remember happening and what we know happened.

Here’s What’s Really Happening When You Get Déjà Vu

No, you haven’t read this before (unless you’re my editor), but I wouldn’t blame you for feeling that way. Pretty much everyone gets that bizarre I-swear-I’ve-been-here-before feeling at some point. Déjà vu is still a pretty mysterious phenomenon, but researchers are putting the pieces together. And even though it can feel freaky, it turns out it might actually be a good thing. So what’s actually happening when you get that weird feeling? There are a couple of different theories about the way déjà vu works, but most of them operate from the idea that it’s a fairly benign — and possibly beneficial — memory issue. Essentially, it goes like this: You’ve seen something that was deemed inconsequential, such as a stranger’s face on the subway, so you “forgot” it. Then, later, you might see someone else who looks very similar to that first person and you get a sense of eerie familiarity, but you’re not really sure why because you don’t readily remember the first guy. It’s almost like your memory is too good, but the result is actually a false memory — you’re confusing the second face for the first. Another theory, called “double perception,” suggests that we’re actually seeing the same thing twice, but we didn’t really register it the first time. Maybe you walk into a new restaurant to meet some friends, but you glance down at your phone to check a text as soon as you get inside. So you did see the layout of the restaurant, but you were immediately distracted. Then, when you look up from your phone, you see it again but it feels like the first time — with a weird sense of having seen it before. But we know that you don’t have to actually have experienced that initial thing firsthand to feel a that sense of familiarity when something uncannily reminds you of it later. For instance, people have traced their déjà vu back to places they only saw in TV shows or photos. So it’s not totally surprising that more recent research — especially with the help of brain imaging and virtual reality techniques — reveals that the process is a whole lot more complicated than an overactive memory. For instance, in a 2012 study published in Consciousness and Cognition, researchers were able to induce a feeling of déjà vu (but not actual memories) in participants by having them walk through virtual 3D locations that shared specific structures. For instance, the windows in a virtual bedroom followed the same shapes as a set of wall shelves in a virtual closet. Another study, this one presented at the International Conference on Memory in 2016, found that feeling might actually be a signal that your brain’s memory checking processes (not memory formation) are at work, explains New Scientist. Here, researchers read 21 participants a series of words that all related to but did not include the word “sleep” (e.g. night, pillow, dream, bed). Then, the researchers asked their participants if they’d heard a word beginning with the letter “s.” They all answered correctly that they had not. However, when they were asked later whether or not they’d heard the word “sleep,” the participants really freakin’ felt like they had heard that word, thanks to all those other words. But they knew, because of the earlier question about the letter “s,” that they hadn’t. That contradiction turned out to be a perfect recipe for déjà vu. Participants’ brain scans also confirmed that the parts of their brains that increased in activity when answering the question weren’t areas we usually associate with memory formation (e.g. the hippocampus) but were, instead, prefrontal areas involved in making decisions. It’s almost as if participants were on their way to creating a false memory of the word “sleep” but their déjà vu feeling told them something wasn’t quite right. So, truthfully, we’re still figuring out exactly what’s going on when you get déjà vu. We can safely say it’s not a glitch in the Matrix, and we can suppose that it’s actually a sign of your mind’s very complicated memory processes working as they should. With any luck, knowing that will help you shake that unsettling feeling next time it happens.

What exactly is deja vu?

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