You enter a place you know you’ve never been before, but a sense of familiarity overwhelms you – a memory you can’t reach. Has it happened to you before?
Most people experience this feeling, known as déjà vu, at some point in their lives. It’s difficult to study because it tends to arise spontaneously and is easily shaken off, experts say. Reproducing it in a lab is complicated, says one of his articles Scientific American.
Sensation can arise when there are parts of the brain that recognize familiar situations not activated properly, said Akira Robert O’Connor, a cognitive psychologist at the University of St. Andrews, Scotland.
When this happens, another area of the brain controls this sense of familiarity versus your recall of past experiences. At that moment, when no memories of actual encounters can be found, the result is an unsettling feeling that you’ve seen it all before, accompanied by the knowledge that you don’t have.
According to O’Connor, when we are in a state of déjà vu, the the experiences we have do not mix well. “At this stage you realize you’ve made a mistake. It looks like a mistake, even if it’s probably the escape from a mistake,” he added.
For some people with dementia, this sense of familiarity occurs without recognizing a mistake. In such cases, people may act as if they have already seen or experienced a certain situation, when in fact they have not.
Déjà vu means “already seen” in French – a term coined by the philosopher Émile Boirac in a letter to the editor of the Revue Philosoplique de la France et de l’Étranger in 1876. In the paper, Boirac speculated that perhaps remnants of forgotten perceptions caused the sensation.
There is now some laboratory evidence that vague similarities between one scene and another can lead to déjà vu. Cognitive psychologist Anne Clearly, from Colorado State University, in the United States, developed, together with her colleagues, a way to induce this sensation in the laboratory.
The experiment involved showing participants virtual scenes that had some subtle similarities. In a 2009 study, they found that watching these scenes was more likely to trigger feelings of déjà vu than watching different scenes – suggesting that maybe there is some environmental kitty for the brain to say “I know this”, even when it has never seen the scene before.
While Clearly’s research shows that slight familiarity can lead to déjà vu, it’s not clear that actual familiarity is necessary to trigger the sensation. “These ideas make a lot of sense, but we’re actually very good at picking out things that are very similar,” O’Connor said.
In cases of déjà vu, he continued, it is possible that the sense of familiarity is accidental. Sometimes, the part of the brain responsible for detecting intimacy can they shoot wildly for no reason.
This random déjà vu hypothesis supports the fact that young people experience more episodes than older people. Younger brains are a little more excitable, possibly firing faster, he said.
Older people may also tend to be less in control of events when feelings of intimacy arise, points out Chris Moulin, a cognitive neuropsychologist at Grenole Alpes University in France. “As I get older, I get frustrated. I used to have a lot more déjà vu than I do now.”he said.