Why do we experience déjà vu?

deja vu

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Déjà vu is the sensation of having gone through a string of events in the past. More often than not, this is not the situation – chances are one has never been in this exact situation, but some biochemical reaction in their brain is giving them the feeling of having lived that moment. Déjà vu is a phrase that is used to describe such a situation and is derived from French, translating to ‘ALREADY SEEN‘.

If we assume our brain to resemble a processing unit, glitches are likely – in the case of déjà vu, the surreal feeling of reliving a moment can be described as a sort of glitch, triggered by some fault in the processing unit of the body, the brain.


About 70% of the people between the ages of 15 to 25 have experienced the sensation of déjà vu, and there is no way of explaining this feeling to those who have not experienced it themselves, thus bringing in a lot of misconceptions about the occurrence and shelving it under supernatural occurrences. Since it’s a fleeting experience that cannot be put into words, it was previously considered a type of PREMONITION. A premonition, in superstition terms, is a ‘vision’ which gives a psychic knowledge of the future. This theory was debunked as soon as scientific reasons and possibilities were brought to light.

Amongst the variety of theories to explain the occurrence of déjà vu, some studies relate it to TEMPORAL LOBE EPILEPSY – a disorder where the temporal lobe of the brain causes seizures – but this was not observed in each case of déjà vu since it occurs with regular people and so this correlation is circumstantial. Nevertheless, déjà vu occurs due to a glitch in the brain but has been proven to be majorly harmless. 

brain game

What causes déjà vu?

Various neural events have been postulated to contribute to the sensation of déjà vu. The mechanism of déjà vu has been explained by a neurologist as the brain performing two kinds of responses at the same time – that of memories and sensation and that of understanding the present events concerning the past ones.

  1. Lag in one part of the brain

As stated above, the brain tries to put in motion two kinds of responses, one of which might take a longer time to integrate with the other, causing a lag. To cover up this time difference and reduce the risks of the brain going out of sync, the random sensation of déjà vu is experienced. This explains why the sensation lasts a few seconds, appropriately the time required for the slower process to catch up with the other.

  1. Experiencing a similar event

While a situation might not be exactly like one experienced before, the brain can interpret it as the body reliving it and cause the sensation, regardless of the differences in the past event as compared to the present one.

  1. A dominant eye

Most humans have a dominant hand, but some have a DOMINANT EYE too. A dominant eye, while as capable as the non-dominant one, can process the event in front faster than the other and send it to the brain. Since it takes a little longer for the other eye to register the same thing and signal the brain, the unconscious, having sent the signal beforehand by the dominant eye, triggers the feeling of déjà vu.

eye o eye

4. Memory mismatch

Memory mismatch is an incidence of the brain, instead of making sense of the events unfolding in front of us, chooses to match it to memory. Since chances are, such a memory does not exist, the person is just left with a feeling, without recollecting the memory. Neurologists claim this occurs when the brain has not had enough rest, experienced by people who do not get adequate sleep.

5. Epilepsy

It was mentioned before that déjà vu may be related to epilepsy, but this is on a case-to-case basis. Everyone experiencing déjà vu might not be diagnosed with epilepsy, but it does occur in epilepsy patients. In epilepsy, a seizure is caused due to the electrical signals in the brain going twisted, thereby losing control over the rest of the body.

While these explanations are purely from a scientific perspective, there are various superstitious reasons markedly attached to déjà vu. Since it has been proven that déjà vu is not harmful to a person, believing these superstitious triggers does not pose a threat to the individual. The superstitious reasons attributed to déjà vu are recollection of past life memories, premonitions or even an unlikely link to the mind of another person (popularly called the tuning fork phenomenon).

While people differ on their views of the cause of déjà vu, each group believes that déjà vu is not harmful to the individual, nor is it an indication of a faulty brain and must be perceived momentary lapse of brain functions. It is properly believed to be proof of a healthy brain since it is the manifestation of the brain’s role in the body and the consequence of it losing control for a fleeting duration of time.

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