What is Déjà Vu?
What if you could experience your memory again- those moments that seemed so surreal you thought that it was real? What if the thin line between past and present becomes blurred?
That is Déjà Vu, one of the most mysterious experiences of human consciousness.
Now, what exactly deja vu is? The term “Déjà Vu” comes from the French word which means “already seen”. Most people experience this sensation of deja vu at least once in their lifetime. Our brain senses a “familiarity” with the situation that has never happened before, and yet, despite its familiarity, it remains one of the least understood experiences in all of neuroscience. Surveys indicate that approximately 60% of people experience Déjà Vu. It is also reported that young people, roughly between the ages of 15 and 25, experience it most frequently. While the exact age range may vary, one thing is certain: the frequency of Déjà Vu experiences decreases with age. It is also more commonly reported among people who travel frequently; those people with vivid dream recall and who engage heavily with their imagination are more likely to experience Déjà Vu.
The lens of Cognitive psychology
Another way to explain Déjà Vu is through the lens of cognitive psychology, specifically memory. People often assume that they intentionally or consciously remember everything they see. However, psychologists note the existence of memories that we possess without realising we have them. While memories we are consciously aware of are called "explicit memories," those we are unaware of are known as "implicit memories." Déjà Vu may well stem from the latter. It can occur when we see a scene identical to or similar to one we saw in the past, something we didn't intentionally memorise but which was stored in our implicit memory.
Despite being a universal experience, Déjà Vu remains difficult to explain. Is it a memory error? A trick of perception? Or does it reveal something deeper that we are not able to interpret, it or doit reveals the way the human mind constructs reality? Scientists, philosophers, and spiritual thinkers have debated this topic for decades; the mystery yet remains unsolved.
Science behind Déjà vu
For many years, researchers viewed Déjà Vu as a curiosity rather than a serious subject to be studied. Because the experience lasts for only a few seconds, studying this in a laboratory seems to be difficult. Scientists have identified that there’s a connection between Déjà vu and the temporal lobe, a region responsible for processing sensory inputs and storing visual memories, processing, and emotional responses. Within its region lies the hippocampus, which acts as a kind of memory librarian. It helps sort experiences, store them and retrieve them when needed.
Recent research suggests that another important structure is involved in déjà vu: the perirhinal cortex, located within the medial temporal lobe. According to cognitive neuroscientist Chris Martin, it is an important contributor to feelings of familiarity even though no actual memory can be retrieved. This region helps the brain to understand whether a situation, person, or object has been encountered before.
For example, imagine sitting in a cafe with your friend; your friend tells a joke with the song playing softly in the background, suddenly you remember that you have lived this moment before. Scientists suggest that the perirhinal cortex may recognise the atmosphere and may feel a sense of familiarity; the hippocampus then tries to locate a specific memory connected to that feeling. When no such memory is found, the brain is left with the sense of familiarity without a source, creating an experience of Déjà Vu.
Researchers believe that deja vu may occur when there’s a mismatch between the brain’s familiarity and recollection systems. Normally, when we see something familiar, our brain can connect that feeling with a specific memory. During the déjà vu episode, the familiarity signal can be triggered even though no memory comes along with it.
Some researchers believe this mechanism is the root cause of déjà vu. A different view suggests that déjà vu is related to temporal lobe epilepsy. According to this theory, seizures or abnormal electrical activity in the temporal lobe disrupt the neural processes that are responsible for handling emotions and memories, thereby producing sensations of déjà vu.
Research has also shown that people with temporal lobe epilepsy are significantly more likely to experience chronic feelings of déjà vu, lending support to this explanation. Of course, the déjà vu experienced by healthy individuals differs considerably from the seizure-related experiences of epilepsy patients. An important distinction is that, while many earlier theories argue that déjà vu is triggered by external stimuli, the temporal lobe epilepsy theory considers it largely independent of outside influences.
As a result, several neurochemical and neurological theories regarding déjà vu, at least to some extent, as a form of brain dysfunction or disorder. This perspective fits with the views of the French philosopher and psychologist Émile Boirac, who originally coined the term déjà vu.
Jamais Vu
Consequently, there exists a phenomenon called Jamais Vu, often seen as the reverse of déjà vu.
An experience where one suddenly finds a familiar situation, place, or person completely unfamiliar and strange. It remains a much less understood topic than déjà vu because fewer people report Jamais Vu. In modern times, some researchers have interpreted it as a form of memory dysfunction related to memory loss, but it still remains largely unexplained.
Even today, despite advancements in science and technology, these common experiences remain unresolved. Researchers have yet to determine whether Déjà Vu and Jamais Vu are symptoms of a disorder, cognitive errors, or something entirely different.
References
- [일상 속 심리학] 데자뷰(deja vu)가 생기는 이유 : 네이버 블로그 https://share.google
- Scientific American – What Causes the Feeling of Déjà Vu?
- Encyclopaedia Britannica. Déjà Vu.