Our memory is remarkable. It allows us to remember things- the good and the bad, and help us make sense of everything around us by preserving details and events that we can later revisit. It’s a crucial ability without which we would have no semblance of ‘who’, ’what’ or ‘when’. But what about remembering things that never happened?

Have you ever, while going about your day, stopped dead in the tracks and thought “I have done this before”? You feel an eerie shiver run down your spine because you know that this is the first time you are doing that thing. But then what made you think it isn’t? And then, just as vivid as the feeling is, it vanishes into thin air in seconds. Before you know it, the familiarity disappears, and everything is back to normal.

Déjà vu refers to the uncanny feeling or sensation of already having experienced a moment that you find yourself in at present. Most times, you cannot point out why it feels that way.

While you have, no doubt heard of this before, the unsettling theories and explanations behind this phenomenon could surprise you.

Because the experience of Déjà vu is so unnatural and fleeting, many believe it to be related to something mysterious, spiritual, or even paranormal. Some may believe that the experience of Déjà vu can be related to experiences or memories from your past life.

Youtuber Diana Magick says that Déjà vu occurs when one’s ‘higher self’ becomes conscious of the self on the earth experiencing life while the 1999 film ‘The Matrix’ describes Déjà vu as a ‘glitch in the matrix.'

While this experience may be a malfunction in the simulated reality we possibly live in, there are a few explanations that are a bit more rooted in science. Although the lack of hard evidence makes it difficult to select the one from the surplus.

Some researchers believe that the experience of Déjà vu may be related to how memories are made and stored in the brain. In support of this theory, scientists have also pointed out that the most common occurrences of Déjà vu are usually seen in epileptic people, mostly suffering from temporal lobe epilepsy. Studies indicate that epilepsy patients report experiences of Déjà vu just before a seizure. They also report that the frequency is high enough for the experiences to sometimes be counted as warning signs for another seizure.

The abnormal electric impulses that contribute to epilepsy can also occur in non-epileptic patients. Thus, some have quoted déjà vu to be sort of a short in the circuits of the brain’.

As there are many different pathways for the brain to process sensory information to store memories, it’s possible that some amount of sensory memory could trigger a feeling of familiarity that can’t exactly point to the memory it is associated with. This is called ‘Mismatch in the Neural Pathways’.

The study of a lab-induced simulation of déjà vu showed that the experience was more related to the area of the brain for decision making, rather than memory. This could mean that the Déjà vu could be the brain doing a very quick form of conflict resolution between what we think we have experienced versus what has actually occurred.

In another theory, the external stimuli like sight, smell, and sound are processed and stored as one event together in the brain. If the processing takes longer for one of them, even by a few milliseconds, the brain can experience it as a different event entirely, and thus making us believe that we may be reliving it.

Another similar theory is known as dual processing. It is the processing of information in both hemispheres of the brain. Any delay in processing at one side can cause Déjà vu. This also gives a rise to the idea that Déjà vu may be a sense of familiarity from extremely recent events, instead of past memories.

The term Déjà vu was coined by a French parapsychologist Emile Boirac in 1876. Now the question that arises here is what made the phenomena so interesting that it drew the attention of someone who worked with the psyche.

At that time, Déjà vu was considered so strange, many people thought of it to be related to the supernatural, much like clairvoyance or mediumship. For many years, the effect was considered a side effect of reincarnation, or possibly even alien abduction.

The name déjà vu itself has become a catchall term for unexpected familiarity, but there are several different varieties that this phenomenon entails.

Deja Entendu refers to the feeling that you have already heard something which is, in fact, new to you.

There is also Deja Pense, which is the feeling that you’ve had a particular thought before when in reality, you haven’t.

Deja Goute relates to food.

It is important to understand that Déjà vu is different from precognition, which is where people have a feeling that they know what is about to happen.

In contrary to Déjà vu, we have Jamais Vu which translates to ‘never seen’ and refers to the feeling that a given situation should be familiar but instead feels foreign, as if you are experiencing it for the first time.

Inducing a Jamais Vu is quite simple - try repeating any word numerous times, and you will notice that it starts to lose its meaning and just appear as a funny conglomeration of alphabets.

Inducing Déjà vu is far more difficult, meaning that studying the sensation is tricky. Mind you, tricky, but not impossible..!

In 2006, scientists at Leeds Memory Group used hypnosis as an attempt to induce Déjà vu. They theorized that the sensation was caused due to a malfunction in memory processing. When the human brain is presented with a new scene, it scans and checks whether elements of this scene have been observed before. If they are, the hippocampus in the brain refires neurons relating to that memory and recognizes the scene as familiar. The researchers hypothesized that Déjà vu occurs when the second part of this process is triggered without the first actually happening, and were successfully able to prove it with their experiment.

Does that explain the mystery then? Well, not necessarily.

Other researchers who tried other techniques for inducing Déjà vu, have come to many different conclusions.

According to a 2014 study in Scotland, Déjà vu may actually be a healthy and important neurological failsafe that perform a conflict resolution function to prevent false memories from forming. The researchers said that it could be the part of a conflict between what participants had seen, versus what they thought they had seen, also known as the concept of ‘false memories.’

In one of the more recent studies, of 2019, Researchers say that people who experience the phenomena more frequently quite likely use more parts of the brain to retrieve memories than others.

As intriguing these ingenious lab explorations of Déjà vu are, it is quite possible that there is a much simpler explanation – that Déjà vu is simply triggered by a forgotten memory.

Now whichever theory you best like the sound of, they are all still just theories.

Despite Science’s best efforts, we still don’t know for sure what causes Déjà vu. The research is a work in progress, but until then, the mystery of Déjà vu remains unsolved.

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