You’ve probably recently had a moment wherein you’ve stopped and realized that, in some subtle detail, it all seems familiar: the same person waiting in line for coffee, wearing the same shirt, or the same car passing you on the way to work every morning. What’s happening? Many claim they’re having a moment that the English language doesn’t quite have a word for.
The term déjà vu — literally meaning “already seen” — was first used by the French philosopher and researcher Emile Boirac in 1876. Ever since, déjà vu has been widely described in music, literature, and films — it could be as subtle as a white rabbit leaping back to its burrow.
RELIVING THE MOMENT
In his novel, “In Search of Lost Time,” author Marcel Proust described the sensation of déjà vu: “I had just seen, standing a little way back from the hog’s-back road along which we were travelling, three trees which probably marked the entry to a covered driveway and formed a pattern which I was not seeing for the first time. I could not succeed in reconstructing the place from which they had been as it were detached, but I felt that it had been familiar to me once; so that, my mind having wavered between some distant year and the present moment, Balbec and its surroundings began to dissolve and I wondered whether the whole of the drive were not a make-believe.”
The odd sense of disconnect Proust describes is perhaps what makes the scene seem uncanny, eerie, startling, or exciting. About two-thirds of people will experience at least a single episode within their lifetime. It typically lasts only a few seconds, or minutes, but people remember the experience in vivid detail for years afterward. Déjà vu occurs in men and women in equal numbers. It happens more frequently in adolescents and young adults, and then tapers off with age.
The recent case of chronic déjà vu was unique, because the man was otherwise healthy, at least so says the co-author of the study, cognitive neuropsychologist Chris Moulin of Pierre Mendes-France University, based in Grenoble. “There was nothing wrong with his brain or memory,” says Moulin. “There was no neurological damage.”
The subject experienced déjà vu on a daily basis, far more than the usual once or twice a year. Sometimes it lasted for up to 30 minutes. The scientists who worked on the study, which was published in December of 2014 in the Journal of Medical Case Reports, believe the cause could have been anxiety. The more he worried about it, the worse the problem became, says Moulin.
A ‘GLITCH’ IN THE SYSTEM?
“Déjà vu occurs when people have the sensation of memory without the presence of memory,” says the psychologist Dr. Akira O’Connor of the University of St. Andrews in the U.K. The “mismatch” when something new feels familiar results in a “false familiarity.”
An area in the brain called the temporal lobe is responsible for memory. One structure in the temporal lobe stores memories of previous experiences, and another is responsible for determining familiarity. The two normally work together seamlessly. The startling sense of déjà vu is thought to occur when they get out of sync.
“We are using memory all the time,” says O’Connor. The brain is constantly creating connections and integrating information, but we are seldom aware of it — until something goes wrong. A “glitch” in the system — misfiring in the temporal lobe — could be the cause. “The brain is signaling that something should be familiar when it is not,” says O’Connor. This is comparable to the neural misfiring that occurs in epilepsy, and it could be that the same mechanism triggers déjà vu in healthy people.
O’Connor has experimented with eliciting déjà vu in the laboratory. He has used hypnosis and lists of words to evoke the unsettling feeling that accompanies one’s misplaced sense of familiarity. More recently, he has been using computerized tests and functional MRI. Although it’s still in its early stages, he says the research might allow scientists to reliably pick apart which regions of the brain are actively producing the déjà vu effect.
A second hypothesis has been proposed by Dr. Anne Cleary, a cognitive psychologist at Colorado State University. Déjà vu is commonly associated with places, and Cleary believes that cues in a new environment may resemble those in an old one. Thus a genuine sense of familiarity may be caused by similar spatial layouts in different places (e.g., hotels, airports, highways). She has devised a 3-D virtual reality experiment in which people encounter the same structures in various scenes within a village (called a “déjà ville”).