deja vu
Must Read Sci-Tech

A phenomenon or A glitch. What really is Déjà vu?

Sometimes you experience a strong sense of familiarity about an event that shouldn’t be felt familiar or the eerie feeling that you have seen this exact thing before. Yes, it is déjà vu.

Most of you heard the word déjà vu and also experienced it. Because it’s a very common thing as 60-70% of people ( or 2/3 population ) experienced it. It is more common in young people of ages 15 to 25 years old and it never occurs before age 8 or 9. Its episodes last between 10 to 30 seconds. So, it’s really a very common thing but at the same time, it’s still a very strange experience.

Talking about myself as a child when I experienced it; I thought that maybe I got some sort of supernatural abilities or I can see the future or maybe I’m the chosen one and there is something epic in my destiny.

I thought all this stuff maybe because I used to watch a lot of cartoons back then or maybe because I spent a lot of time imagining things.

But when I share this experience with others, I came to know that almost everybody experiences it and it’s a very common thing and also that I’m not the chosen one.

But after knowing that it’s a very common thing and it is experienced by all; I still don’t know what really déjà vu is.

So, if you also want to know what it is then let’s stay with me as I’m going to dig deeper into this déjà vu.

Why Déjà vu is called Déjà vu?

The word déjà vu was first used by Émile Boirac (a French philosopher, parapsychologist). He used it in a letter to the editor of the Revue Philosophique (an academic journal) in 1876. Later on, he used it in his book “L’Avenir des Sciences Psychiques” (The Psychology of the Future).

Déjà vu

The word déjà vu is pronounced as “day-zhaa-voo” and actually is the combination of two French words. Déjà means ‘already’ and vu means ‘seen’, together it is “already seen”.

Why Déjà vu happens?

In the case of déjà vu, the question is not what but why, as almost everybody knows what it is but not why it happens?

In the earlier assumptions, déjà vu episodes were considered to have some link with epilepsy and seizures in the brains but that does not explain why people without epilepsy experience déjà vu.

Unfortunately, there is no single scientific explanation of déjà vu as this experience is brief and occurs without any notice; that makes it nearly impossible for scientists to record and study it. So, scientists can’t simply just sit around and wait for it to happen to a subject because it might take years and also it has no physical manifestation, which means you can’t detect it through any scan. Due to this lack of hard evidence, there’s been a surplus of speculation over the years. But there are different theories (about 40) that explain this strange experience.

Now let’s discuss some prevalent theories.

Dual Processing – Mistake in the Present

The idea behind this theory was proposed by Robert Efron, that new novel stimulus hits our brain, it processed twice but sometimes a delay occurs in neurological response. So, when that second time, it runs through our brain the brain takes it as something that’s already familiar.

An illustration portraying the concept of dual processing

Didn’t get it? No problem.

Let’s take an example, you are in a restaurant and a waiter drops a dish of pasta, at that moment there is a lot of information processing going on in your mind like flailing arms of waiter, his cry for help, the smell of pasta in that dish. All this information zip through pathways and processed into a single moment within milliseconds. Most of the time everything is recorded in sync but this theory asserts that sometimes there’s a slight delay in information from one of the pathways that cause a un-sync which results in the déjà vu.

But why this un-sync happens?

Our various sensory inputs like the smell, sight, hearing are normally processed separately and then mixed together as a single moment so if one of the inputs processes earlier or later it’ll cause the un-sync.

For instance, you saw a car at very high speed going from your left to right, this information gets from your left eye to your visual cortex just before the information from your right eye gets there, these two events happen in a very short amount of time that the left eye information is not stored as memory yet but since your brain received the information twice it feels familiar.

But another explanation of this un-sync is that our brain is divided into two cerebral hemispheres i.e. left and right. The temporal lobe of the left cerebral hemisphere is responsible for sorting the incoming information. It receives this information twice, once directly and once again after a detour through the right cerebral hemisphere. There is a slight delay (of milliseconds) in the information arrival but if that delay becomes a little longer, the brain put a wrong timestamp on it and register it as previous memory as it is already processed.

Conclusively we can say, the difference in arrival times of information causes the brain to interpret the late information as a separate event. So, when the brain plays the recorded moment, it feels like it happens before and in a sense it actually has.

Hologram theory – Confusion of the Past  

Hologram theory was proposed by a Dutch psychiatrist named Dr. Hermon Sno.

According to this theory, memories are stored in our brains in the form of holograms, and in holograms, you just need one fragment to see the whole picture, as you can recreate the entire three-dimensional image from any fragment of the whole.

For example, if you cut the substance that creates the hologram into smaller pieces no matter how small, it’ll still show the whole hologram but it’ll be fuzzier and low res.

Let’s take that restaurant example again, you are in the restaurant, you are eating your meal but suddenly you see the tablecloth. When you see that tablecloth and scan the pattern of that tablecloth, a distant memory brings up from deep within your brain.

Let’s assume that your brain has identified that tablecloth with the one, that you saw in past at your grandma’s house. But instead of remembering that you have seen that tablecloth at grandma’s house, your brain has summoned up some remnant of an old memory without identifying it. This leaves you with a sense of familiarity but no complete recollection of that specific memory just like the fuzzy little piece of the hologram.

Although you have never been in this restaurant but you have seen that tablecloth before but are just failing to identify it.

Divided Attention

This theory was proposed by Dr. Alan Brown and it states that déjà vu occurs when our brain subliminally takes in an environment while we are distracted by one specific object. When our attention returns, we feel as if we have been here before.

Let’s take that restaurant example one more time to understand this theory, you are in the restaurant, you are waiting for your meal, this time you focused on a fork on the table and didn’t observe the falling waiter and tablecloth as you did in previous examples.

Although your brain is recording everything in your peripheral vision unconsciously and when you finally pull yourself away from fork, you think that you have been here before because you really have, but were not attentive.

Leaky Processing Theory – Brain’s Malfunctioning

To understand this theory, you should know about how memory is stored in the brain.

According to “Modal Model of Memory” there are three stages of memory

  • Sensory Register
  • Short-term
  • Long-term

Each of our senses consists of sensory registers, they do not store any information, they only act as buffers, information is kept here just for fractions of a second.

After that information is transferred to the hippocampus and now it is considered as short-term memory. Here this short-term memory is kept for about 30 seconds and it is also the place where the memory is sorted as important or unimportant.

If the information is important then it is labeled as long-term memory but it is not stored in a specific area of the brain, like short-term memory instead of it, the long-term memory is stored at various places in the cerebral cortex.

Let’s get back to the theory.

Leaky Processing Theory says that somehow some little bit of stimuli get through from our working memory (short-term memory) to long term memory without being sorted (in the hippocampus) and although it’s new, our brain mistakes it as something familiar as it’s in the long-term memory.

Conclusively we can say that according to Leaky Processing Theory we experience déjà vu when our brain makes a mistake in memory storage.

Memories from other sources

This theory is also related to memory.

According to this theory, we have a bunch of memories stored in our brain but not all of these memories are from our own experiences. Some of them are from books we have read; movies, pictures we have seen.

We have very strong memories related to what we have seen or read, but we don’t actually have experienced these memories. These memories are then pushed back in our minds with the passage of time. When we experience or see some events similar to those memories, we experience a shadowy feeling or say déjà vu.

Let’s take that restaurant example for one last time, you are in the restaurant and you feel the sense of familiarity because when you were a child, you have watched a movie in which you have seen similar kind of restaurant but didn’t remember the movie.


All these theories have some ideology that makes us think that these are correct but at the same time, they are not completely proved, as déjà vu is very difficult to examine, that’s why they are still theories.

Maybe in the future with more advancement in medical science, cognitive psychology and technology help us find the definitive cause of déjà vu.   

Until then whenever you experienced déjà vu, take a moment and think about it. Have you been distracted? Is there a familiar object nearby? Is your brain working slow? Is it a glitch in the memory storage? Or it is just because of a forgotten childhood memory?

Interesting Facts

  • Jamais vu is the exact opposite of déjà vu, it is the eerie feeling of unfamiliarity towards a person, a place or a word. It means literally “never seen”.
  • The scientific name of déjà vu is “Paramnesia”.
  • If we just go with the literal meaning déjà vu, it only deals with the sense of vision.

That’s why we have the whole family of déjà experiences

  • déjà entendu – already heard
  • déjà éprouvé – already experienced
  • déjà fait – already done
  • déjà pensé – already thought
  • déjà raconté – already recounted
  • déjà senti – already felt, smelt
  • déjà su – already known (intellectually)
  • déjà trouvé – already found (met)
  • déjà vécu – already lived
  • déjà voulu – already desired
  • déjà arrivé – already happened
  • déjà connu – already known (personal knowing)
  • déjà dit – already said/spoken (content of speech)
  • déjà gouté – already tasted
  • déjà lu – already read
  • déjà parlé – already spoken (act of speech)
  • déjà pressenti – already sensed
  • déjà rencontré – already met
  • déjà rêvé – already dreamt
  • déjà visité – already visited

But conventionally we use déjà vu for all these experiences. 

+ posts

Leave a Reply

Your email address will not be published. Required fields are marked *