SCIENCE Q&A: What causes déjà vu?


By Lindsay Nemelka

Staff Writer

Many people have reported the strange feeling of having experienced something twice—having the same conversation with the same cup of coffee in a café or the feeling like you’ve been in an exact spot before, even though you know it’s your first time there.

The Matrix movies explain déjà vu as a glitch in the all-encompassing reality program that runs human lives. Other than people being hard-wired in an apocalyptic machine-ruled world, the explanation of the déjà vu “glitch” isn’t so far off.

WHAT IS DÉJÀ VU?

The term déjà vu, meaning “already seen,” was coined by French supernatural researcher Emile Boirac in his book “The Future of Psychic Sciences.” Boirac described déjà vu in 1876 as a phenomenon where an overwhelming sense of familiarity — in a situation that has never previously been experienced — occurs. Sometimes a feeling of “eeriness” or “strangeness” accompanies the familiarity.

HOW OFTEN DOES DÉJÀ VU OCCUR?

Various surveys have shown that approximately 70 percent of the population reports experiencing déjà vu. It is more common in young adults ages 15-25, declining with age.

WHAT CAUSES DÉJÀ VU?

There are over 40 different theories circling on what causes déjà vu, from medical explanations, psycho-analyses, and mystical or religious beliefs. For example: many spiritualists believe that déjà vu is an act of precognition, prophecy or even a memory of a past life.

MEDICAL OPINIONS:

Because déjà vu is common in normal, healthy individuals, many researchers can only speculate how and why it happens. Some psychiatrists believe that déjà vu is merely a mix-up of the brain’s ability to distinguish the present from the past. This memory anomaly (or Associative Déjà Vu) gives the brain a false impression of the experience being recalled instead of recorded. This is also why an “eerie” or “unsettling” feeling accompanies the familiarity—the brain knows of the impossibility of the situation previously occurring.

Often, the subject forgets the specific circumstances in which déjà vu took place, but is still left with the feeling of the experience.

In his 2010 article for Psychology Today, Art Markman, Ph.D in cognition at the University of Texas, states that we have two kinds of memory: the memory of occurrences, and the memory of places (called source memory). Déjà vu, he said, is a feeling of familiarity created by the source memory of a similar situation that occurred previously.

“We are not so good at retrieving a memory based just on the configuration of objects,” Markman said. “If you are in a place that has some unfamiliar objects, but they are set up similarly to a situation you have experienced before, you will get a feeling of knowing, but you won’t actually retrieve any specific memory for the place… If the configuration is nearly identical to one that you experienced before, though, then you may get a powerful feeling of knowing. That is, you may get a sensation of déjà vu. In the end, though, the experience of déjà vu is just an extreme reaction of the system that your memory uses to tell you that you are in a familiar situation.”

ASSOCIATIONS WITH MEDICAL DISORDERS

Biological Déjà Vu, on the other hand, has been associated with epilepsy in the temporal lobe, occurring right before, or even during, a seizure of the temporal lobe. The temporal lobe is the region in the brain where memory is stored. Though this seizure in the temporal lobe doesn’t happen in healthy adults, the same regions are most likely involved in cases of déjà vu.

DÉJÀ VU EXPLANATIONS THROUGHOUT HISTORY

Freud called this déjà vu familiarity “the uncanny,” and attributed the feeling to similar situations in dreams (and of course, suppressed desires).

Carl Jung attributed déjà vu to tapping into the collective unconscious.

An article written by Dawn Stanton for Physorg.com quotes Claire Flaherty-Craig, a neuropsychologist at Hershey Medical Center who said déjà vu was once thought to be a delayed reaction of visual input recording in the brain. “There was a long-standing theory about a visual disconnect,” she said. “It was thought that one hemisphere of the brain would process the visual information first and so the delayed information reaching the other hemisphere was processed like a memory.”

However, recent studies done on the blind have challenged this idea, and Flaherty-Craig noted at least one case where the blind individual reported déjà vu involving hearing, touch and smell.

So remember—next time you see the same two black cats cross your path, you’re either trapped in the matrix, or you’ve experienced the strange, eerie phenomenon known as déjà vu.

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