Déjà vu: All about that feeling of familiarity

“Been there. Done that” is a common saying in English. Did you know that “Been there, Seen that” is, too? We just don’t say it like that. Instead, we use the French term “déjà vu” which means ‘’already seen’’. We’ve all had that feeling of familiarity when we are doing something we’ve never done before (or at least that we can’t remember doing). For example, touring a cathedral in Spain or feeling that you’re having the topic of conversation during the same dinner with the same friends even though you have never been to that restaurant before nor talked about that specific topic. That’s all déjà vu. So, what is this déjà vu? What are the causes and how is it related to disorders such as anxiety, dissociative identity disorder, and schizophrenia? How is it affected by our brain? What are the theories that surround it and what is its pharmacology? How is it explained? What are some closely related terms? Keep reading to find out.

Déjà vu
Déjà vu

What is déjà vu?

Déjà vu is the feeling that someone gets when they feel they have already lived through the present situation before. It’s a feeling of familiarity, like with déjà vécu, which is the feeling of already having lived through something. Both are feelings of recollection.

Scientific approaches explain this feeling as an anomaly and oddity of memory because despite the strong sense of recollection felt, the place, time, and context of the “previous experience” are unknown or uncertain. Training cognitive skills can help reduce those anomalies or oddities. 

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Types of déjà vu

There are two types of déjà vu- the non-pathological and the pathological.

  • The non-pathological type is a characteristic of healthy people, whom about two-thirds feel déjà vu.
  • The pathological type is often associated with epilepsy and can also be felt with hallucinations which can be an indication of psychiatric or neurological illnesses.

Statistically, about 70% of the human population experiences déjà vu in one way or another. It most often occurs in people between 15-years old and 25-years old.

Causes of déjà vu

Although déjà vu is something that happens in every 2 out of 3 people, it’s not as commonly studied. However, there are three big theories as to what causes deja vu.

1. It’s theorized that you’ve been somewhere or experienced something similar. Walking into a hotel lobby and feeling déjà vu could be triggered by the fact that the furniture is arranged the same way as your childhood home living room. A study done in 2009 that was published in the journal Psychonomic Bulletin & Review gave participants a series of photos of simple things such as a fenced backyard or a locker room. After a while, the participants felt déjà vu due to the fact that the images were put together in a similar way. The conclusion of the study is that there’s a likely connection between feelings of familiarity and déjà vu.

2. The most likely culprit is that your brain is a bit out of whack. Déjà vu could be a sign of temporal lobe epilepsy. It can also be chalked up to the neurons in the brain firing at the wrong time and the brain becomes overpowered with a feeling of déjà vu.

3. Another theory is that people who travel a lot and can recall their dreams are more likely to feel déjà vu compared to people who don’t travel and can’t remember that dreams. The theory works in the sense that people draw their memories on a wide range of sources. If they travel a lot, they will draw from their travels and the memories made during them. Traveling all over gathers lots of different kinds of memories and makes other environments that the person is in feel familiar, too. Our memory and other cognitive skills are involved in déjà vu, be sure to understand how your brain works.

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Anxiety and déjà vu

Most of the time, déjà vu is associated with temporal lobe epilepsy or dementia. However, scientists have recently discovered that psychogenic deja vu also exists. This type of déjà vu starts in the mind, not physiologically. The first case of psychogenic déjà vu was reported done on a 23-year-old British male who had experienced chronic déjà vu for about 7 years. He had a history of anxiety and OCD tendencies. His anxiety worsened to the point that he had to take a break from this studies. During the same time, he began to experience frightening deja vu episodes that became even more intense when he went back to university. Eventually, he stopped reading books, newspapers, magazines, listening to the radio, or watching TV because he felt he had seen it all before. In 2008, he went to a neurologist who found nothing wrong neurologically- nothing showed up in his scans. The theory now is that this man’s anxiety triggers a misfiring of neurons in the temporal lobe (the part of the brain that deals with familiarity and recollection).  

Dissociative Identity Disorder and déjà vu

Déjà vu and Dissociative Identity Disorder have a big thing in common- they both are associated with feeling a dissociative or out-of-body state. When someone is in a dissociative state, they actually lose their normal sense of emotions, actions, thoughts, and surroundings. We can actually feel “beside ourselves’’ because we no longer feel our own psychological or cognitive processes (because they feel unreal). A dissociation can be a normal, or it can be symptomatic (meaning it’s a symptom and sign of a psychiatric or neurological issue).

Schizophrenia and déjà vu

There is no actual association between déjà vu and schizophrenia. That said, déjà vu can be a sign of schizophrenia. One study took 113 people with schizophrenia and 386 people who aren’t schizophrenic for control subjects. People who had schizophrenia experienced less déjà vu (53.1%) than the control group (76.2%). The characteristics of their déjà vu were similar. Nevertheless, the schizophrenic subjects felt longer and more monotonous deja vus- unpleasant physical and mental experiences. The study concluded that the lack of frequency of déjà vu experienced in the schizophrenic patients can suggest that it’s a non-pathologic phenomenon.

Déjà vu
Déjà vu could be caused by misfired neurons

The brain and déjà vu

Déjà vu is strongly associated with the temporal lobe. It can be a symptom of temporal lobe epilepsy, actually. The dreamy state that people feel while in déjà vu can happen in occurrence with a temporal lobe seizure. Right before the seizure happens, actually. The feeling of familiarity comes from mistimed and misfired neurons that cause (temporary) glitches in the processing of incoming information in the brain (specifically, the temporal lobe).

Déjà vu could also be happening because the brain is struggling to balance and process multiple pieces of information at a time. For whatever reason, it’s unable to do it well and can’t align the information correctly. This lack of being in sync (synchrony) can also be what causes deja vu in the brain.

Theories of déjà vu

Previous memories

We all have stored memories from books we’ve read, movies we’ve watched, as well as what we have experienced in real life. The previous memories theory proposes that those stored memories can be really strong without us having actually experienced them. The memory gets pushed back into the brain into long-term memory when we don’t use it- but we don’t forget it. Then, when something familiar comes by, we feel that deja vu. For example, you watched the TV show Friends a lot as a young adult. While you may have not thought about the cafe where all the friends go and where Rachel works, The Central Perk, if you visit the cafe as an adult, without remembering the TV show, you’ll feel that the location is familiar to you. While that cafe isn’t part of your real memory because you hadn’t experienced it in real life before, it did form part of your previous memories.

Dual Processing, Delayed Vision

The theory bases itself on how our brains process new information and how our brains store our long-term and short-term memories. The dual processing theory proposes that a  delayed neurological response causes deja vu- information enters the brain’s processing center in more than one pathway. Having more than one pathway causes confusion, a blend of information, and the information isn’t synced correctly. The left side of the temporal lobe is in charge of storing new information and receives new information twice (with tiny millisecond-long delays between transmissions of new information). If the second transmission of new information is delayed slightly longer than those milliseconds because it took a different brain pathway, the brain might put the wrong time stamp on the information and register it as a previous memory because it’s already been processed.

Pharmacology of déjà vu

There are certain drugs that increase the likelihood of déjà vu happening. Sometimes, a combination of different drugs causes the phenomenon. One study looked at a healthy man who was taking phenylpropanolamine and amantadine together. While taking the two medications in order to relieve his flu symptoms, the man experienced severe déjà vu. This occurrence of déjà vu while taking cold medicines is thought to be the result of a hyperdopaminergic reaction (essentially, the brain releases lots of dopamine) in the mesial temporal parts of the brain.

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Explanations of déjà vu

There are two big explanations so far about why déjà vu occurs- the dream-based explanation and the memory-based explanation. The dream-based explanation is based on the theory that the feeling of a “previous experience” actually stems from a dream. Meaning that the person had seen the place, experienced the experience before, but just in a dream. That’s why the person can’t place when or where they felt the déjà vu before, they just know that they feel it then. Well, maybe they previously experienced it in a dream.

Déjà vu
Déjà vu- the dream based explanation of the phenomena

Considering that research has shown that déjà vu has been associated with good memory functions, the other theory, the memory-based explanation believes that the similarity between a déjà vu-inducing stimulus and an existing (or not existing) but different memory can lead to the feeling that the experience or the event happening has already happened in the past. By coming across something that brings up the associations of a feeling, sensation, or experience that can’t actually be remembered is what leads to déjà vu. One study tried to give participants the “déjà feeling” by using hypnosis to induce a posthypnotic amnesia for things they had already seen. When they did the experiment again a while later, 3 of the 10 participants felt what the authors called paramnesias.

Another theory that isn’t involved in either the dream-based nor the memory-based ones is that déjà vu is actually the occurrence of cryptomnesia. It’s the idea that information learned is never truly forgotten and is stored in the brain. When something happens that solicits this pre-contained knowledge, the feeling of that déjà vu familiarity occurs because something being experienced has already been experienced. Other people suggest that the phenomena come from a memory process of reconstruction instead of our brains recalling the “past”.

Related terms to déjà vu

What is déjà rêvé?

Coming from the French “already dreamed”, déjà rêvé is the feeling people get when they feel they have already dreamed something that they are now experiencing in real life. It’s like the opposite of lucid dreaming. One study looked back on medical reports from epileptic patients between 1958 and 2015. They found that déjà rêvé is actually common after someone experiences electric brain stimulation- a common treatment for epilepsy and its symptoms.  This study shows us that déjà rêvé is just the result of something happening physiologically in the brain.

Déjà vu
Déjà vu is the opposite of jamais vu (never seen)

What is jamais vu?

Coming directly from the French ‘’never seen’’, jamais vu is the psychological term that is used to describe any familiar setting that isn’t familiar to the observer. It’s essentially the opposite idea of déjà vu- which is why jamais vu is also called vuja de and véjà du. It can be associated with amnesia, aphasia, and epilepsy. In theory, the person who is feeling the jamais vu is in a delirious or intoxicated state. Have you ever looked at a word for so long that you start to think it isn’t written correctly, even if it’s your name? Well, a study done by the University of Leeds asked 95 people to write the word ‘’door’’ 30 times in 60 seconds. 68% of the participants said that they felt some sort of jamais vu because they began to doubt that the word ‘’door’’ is a real word.

What is déjà visité?

Coming from the French for ‘’already visited’’, it describes the specific déjà vu feeling you get when you feel familiar with a physical place you’ve never been to. For example, traveling to Spain, touring a cathedral, and feeling you had already been there before.

What is presque vu?

Coming from the French ‘’almost seen’’, presque vu is the strong and intense feeling of being right of the edge of an incredible epiphany or revelation without having actually achieved the revelation or epiphany yet. It’s a feeling often associated with a sense of incompleteness or near-completeness.

What is déjà vecu?

Coming from the French for ‘’already lived through’’ or ‘’already experienced’’, it’s like that dinner with the same friends and the same conversation that feels like a repeated experience even though you have never been to that restaurant before nor talked about that specific topic.

What is déjà entendu?

Coming from the French word ‘’already heard’’, déjà entendu is what happens when someone feels sure about having heard something, even though the details are unknown or imagined.

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