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
