What is Deja vu?
Deja vu is a mysterious experience that every human being comes across once or several times in their lives. Deja vu is a feeling, where a person believes that he or she has already experienced what is currently happening to them. And hence, Deja vu in French literally means, ‘Already seen’. This shouldn’t be confused with Deja vecu which means the feeling of already lived through something. Deja vu is more a sensation of recollection. Deja vu is believed to be a sense of recalling something that has probably happened before. Scientists explained that while experiencing Deja vu, the person’s sense of recollection is the strongest and hence he or she gets the impression of it having happened before. But the recollected experience of the person, whenever and where ever that happened has probably never occurred or it is highly impossible for it to have existed. Scientists have dismissed the previous explanations of Deja vu that stated that Deja vu is a precognition or a prophecy.
People who suffer frequently with Deja vu or who frequently experience it for prolonged times may have some neurological or psychiatric illness as these symptoms are closely related to hallucinations.
Types of Deja vu
There are mainly two types of Deja vu occurrences:
- Deja vu that occurs when a patient has an epileptic attack. This is pathological and has several explanations to why it happens.
- The other is a psychological phenomenon that occurs in healthy people, which is non-pathological and has no real explanation as to why or how it occurs.
Deja vu Explanations
Many people, scientists, and scholars alike have tried to explain the phenomenon that is Deja vu in their own terms. While some say that they are linked to certain mental disorders, other have stated that it can be caused due to the usage of certain drugs. Some others have also tried to give memory and dream based explanations.
Deja vu and Mental Disorders
Researchers have tried to find parallels between Deja vu and mental disorders like Anxiety, Schizophrenia, and DID (Dissociative Identity Disorder.) They found none whatsoever. Some have tried to explain that Deja vu occurrences may have similar relations to how body jolts happen to people while they sleep. This is the feeling of falling off a higher ground while sleeping in a person. Epilepsy happens on similar grounds but at a much higher level and it is pathological. Jolts happen due to small neurological aberrations inside the brain and it is believed that Deja vu may also happen due to the same type of aberrations. And this causes the incorrect feeling or recollection that the incident has already happened in a person’s life.
In recent years they have cleared out that Deja vu has nothing to do with mental disorders or and that it is not a pathological illness.
Deja vu and Drugs
A man experienced the mysteries of drugs and Deja vu when he once tried to cure his flu. Taiminen and Jääskeläinen reported in 2001 that this man took amantadine and phenylpropanolamine when he got struck by the flu and what he experienced next were a series of Deja vu like occurrences. The man was so fascinated by the incident that he repeatedly took the drugs until the end of the dosage and reported it to psychologists for case studies. So yeah, Deja vu can occur due to the intake of certain drugs and drug combinations. This makes the person feel like he has already seen the incident happen before. Taiminen and Jääskeläinen have made speculations that Deja vu can happen because of hyperdopaminergic action within the mesial temporal parts of the brain.
Deja vu and Memory
Deja vu is a wonderous phenomenon and so is our brain and it’s cognitive process. The human brain, the most advanced vital organ ever created or exists is so full of mysteries that we are yet to decode a huge amount of them. Deja vu is one such quasi-explained mystery and researchers have stated that Deja vu is linked strongly to a human’s excellent memory. It is explained that the brain stimulus that evokes Deja vu is extremely similar to the somewhat different, existing or non-existing memory trace. So it is possible that something very similar has happened to the person before and he or she experiences Deja vu with the impression that it is the same event and that they have already experienced it before.
In 1941, Banister and Zangwill tried to create Deja vu experimentally, using hypnosis on a group of people. They gave the participants posthypnotic amnesia wherein they could recall things they forgot in real life while in the hypnotized state. Later on, after the procedure, 3 out of the 10 participants were able to recognize the forgotten material. They named this as Paramnesias.
Cleary proposed familiarity based Deja vu, wherein a person’s sensation that what is currently happening to them has already happened before in the past. Where there is a connection of familiarity between Deja vu and the previously occurred incident which cannot be recollected. So in 2012, a Virtual Reality study took place to test this particular theory out. They played out a scene on virtual reality of a spatial layout which was very similar to a previous scene that existed before but isn’t remembered. So while watching the new scene, one does not recollect the previous scene but knows the similarities between the two of them. So the previous scene, though not recognized, still has a strong effect on the new scene, thus causing the feeling of familiarity based Deja vu.
Cryptomnesia is explained as a forgotten memory, that comes back to a person and he or she won’t remember it as an old forgotten memory and hence will consider it a new memory made. Deja vu has been closely connected to this particular memory mystery as well. The parallels are drawn when a person forgets a memory, but something similar happens and there are chances that he or she will experience the feeling of familiarity because he or she cannot recollect the event that has really happened in this case. So what’s fascinating is that Deja vu also occurs in a similar fashion wherein the person tries to make a connection with the happening event to the happened event. But in the case of Deja vu, unlike cryptomnesia, the event may not have ever occurred and is extremely different and deviating from the current memory.
However, the most promising memory related Deja vu explanation was probably given by Boston Veterans Hospital’s, Robert Efron. In 1963 he explained that Deja vu occurs because, while normally the temporal lobe of the brain’s left side sorts out incoming signals, in this case, the signals enter the temporal lobe twice, thus giving the person a Deja vu experience. This is why the person recollects the most recent signal, that has immediately been processed and this signal is the event that is happening currently. The old signal becomes goes by but leaves an existing impression to the person that it has occurred before already.
Deja vu and Dreams
The most obvious explanation is that the event that seems to have had already occurred is probably a dream that a person dreamt before (and has forgotten), but has then recollected it in the form of Deja vu. So basically the dream theory is that the event that is occurring has already occurred before because the person dreamt of it and has later forgotten about it but the current event triggered the recognition process of the brain.
Deja vu and Jamais vu
Jamais vu (French for ‘never seen’) is quite the opposite of Deja vu. A person forgets what he has really experienced but still has a sense of familiarity with the event. One can say it is amnesia, but there is a difference, although they are closely associated. The person believes that he has seen or experienced a particular situation for the first time, but somewhere in the back of his mind, he or she knows that’s really not the case. Deja vu is the total opposite, the feeling that something has happened before when in reality it may not have happened at all.
The best way to explain Jamais vu is when a person forgets the names of people, places he already knows and has been to. Timing, repetition, and familiarity can cause a severe case of Jamais vu. Once University of Leeds’ Chris Moulin asked some volunteers to pen down the word ‘door’ for 30 times in a minute. 64 out of 95 students experienced Jamais vu. Some of those students stopped believing that door is an actual word during the experiment.
Another close phenomenon is Presque vu (French for ‘Almost seen’). The person feels that he or she has had a near, strong insight or epiphany about an event but never reaches a conclusion to how or where he or she has actually seen it. Frustration is one feeling that can be associated to Presque vu.
It is extremely hard to come to a conclusion as to what actually causes the sense of Deja vu. While having so many scenarios to explain the phenomenon, no one actually understands what causes it to happen. We just know it happens.