Deja Vu

Ever had this eerie feeling where you thought that the present was already experienced by you? That somehow you had lived in that exact moment before? Well, it certainly appears to look like a minuscule part of the past interfering with the present. But is that really what it is? 

This strange feeling of vague familiarity with completely novel experiences is known as Déjà vu. It is a French term, literally meaning “already seen”. Déjà vu is very commonplace. In fact, it is reported that 60 to 70 percent of people have had experienced Déjà vu at least once (Brown, 2003). Charles Dickens describes this feeling in his novel, David Copperfield. He recounts it as a feeling “that comes over us occasionally, of what we are saying and doing having been said and done before, in a remote time- of our having been surrounded, dim ages ago, by the same faces, objects, and circumstances- of our knowing perfectly what will be said next, as if we suddenly remember it.” It is a complex phenomenon, with no one universally accepted theory behind it. Surprisingly, even though Déjà vu is vastly common, the subject has received very poor scientific attention. And thus, it remains one of those out of the ordinary brain phenomena with no proper explanation. But from research that has been done on this subject, some prominent theories have thrown light on the possible explanations behind this baffling phenomenon. 

SPLIT PERCEPTION THEORY

This theory of Split Perception posits that Déjà vu sets in when we look at a scene subliminally, not giving it enough time to register consciously. But on an unconscious level, information gets registered.

In this case, a person processes the sensory input twice, one after the other.

According to this theory, when we are exposed to a particular scene and then are momentarily distracted by a voice or a sight, we lose our attention on the surrounding. But all the information regarding the scene that we briefly had looked at, gets registered into the brain unconsciously. Thus, when we regain our awareness after the distraction, we feel that we have somehow already experienced that moment, bringing in this strange feeling of familiarity. Here, the first sensory input is very brief and diminished. The second sensory input, however, seems oddly familiar because of the already processed first brief input.

DUAL PROCESSING THEORY

This theory is generally based on the idea of how new information is processed and how the sensory inputs travel to the processing centres of the brain. Essentially, Dual Processing theory suggests that human beings experience Déjà vu when two cognitive processes are out of sync. In 1963, Robert Efron tested his proffered idea that a delayed neurological response causes Déjà vu. This study was carried out at Veterans Administration Hospital in Boston. Today, this theory is one of the most widely accepted explanations behind Déjà Vu.

Efron found that the sorting of the incoming signals takes place in the temporal lobe of the brain's left hemisphere. He proposed that signals entered the temporal lobe twice, once directly in the left hemisphere and once travelling through the right hemisphere, thus causing a delay between the signals.

So, if the two signals were occasionally not synchronised accurately, then they would be registered as two different experiences, with the second seeming to be a re-living of the first. (Robert Efron, 1963)

One of the main reasons why the cause behind this phenomenon is still blurry is its inconsistent nature. Also, the difficult process of inducing the experience in a controlled environment for research studies accounts for the poor attention that this subject has received.

Vast number of theories have been put forth, many are supported by various studies and a few have the potential to uncloak this ambiguous phenomenon provided they are further more strongly supported by new research studies. In today’s world, where it is firmly believed that nothing is impossible and with all the significant development in science, we can surely hope that this baffling phenomenon will no longer be a mystery.

- Disha Pushilkar, SYBA