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Deja vu refers to the feeling of having already lived through a current situation, when it is completely new. Scientists have been trying to find the cause of this phenomenon and the factors that provoke it for more than a century. It was only recently, in the early 2000s, that research provided some elements of the answer. A team of psychologists from Colorado State University has investigated the matter again: they have managed to identify one of the factors that hide behind this strange sensation.
The term deja vu was first mentioned in 1876 by the French philosopher Émile Boirac in his book The future of psychic sciences. You have probably already experienced it, since the phenomenon affects two thirds of the population; however, its frequency decreases with age. This impression usually lasts only a few seconds and the so-called resemblance to a past experience refers to more or less details.
After decades of research, exploring various possible causes, from mental dysfunction to paranormal manifestation, it was the American psychiatrist Alan Brown who really helped advance research on the subject. In 2003 he reviewed dozens of retrospective and prospective studies, as well as case studies, to take stock of the knowledge gained on the subject over more than a century. ” Deja vu appears to be associated with stress and fatigue, and shows a positive relationship with socioeconomic status and education. “, he points out in his review article.
A sensation based on spatial resemblance
Brown also identified the most common trigger for the feeling of deja vu: it would be a scene or a place. The second most common trigger, according to him, would be a simple conversation. By exploring the available medical literature, he also found clues about a possible association between deja vu and certain types of seizure activity in the brain. ” His work has served as a catalyst for scientists to design experiments to investigate deja vu. says Anne Cleary, a professor of cognitive psychology at Colorado State University.
Therefore, Cleary and his collaborators undertook experiments designed to test hypotheses about the possible mechanisms of deja vu. They were particularly interested in a hypothesis that has been explored many times, which is based on the Gestalt law of familiarity. Gestalt (or “form psychology”) is a theory according to which mental perception and representation treat phenomena as complete forms and not as the juxtaposition of individual elements.
The Law of Familiarity suggests that we always perceive the most familiar and meaningful forms. The hypothesis tested here holds that déjà vu can occur when there is a spatial resemblance between a current scene and a past scene of which the individual has no memory. Therefore, the arrangement of furniture or other objects in a room could be very similar to what you may have observed elsewhere in the past, and thus cause deja vu.
” According to the hypothesis of the familiarity of the Gestalt, if this previous situation has a similar disposition to the current situation and you do not have the spirit, it is possible that you do not have a strong feeling of familiarity for the Current situation “, explains the specialist.
An illusory predictive ability, due to a cognitive bias
Cleary and his team tested this hypothesis using virtual reality. Thus, they immersed the study participants in scenarios created from scratch; some had exactly the same spatial arrangement, although they were very different. Unsurprisingly, deja vu was more likely to occur when people were in a scene that contained elements arranged identically to another earlier scene they had seen but didn’t remember.
This experiment confirmed that the spatial similarity of a new situation with a situation in memory, but not consciously recalled at the time, is in fact one of the factors that contribute to the appearance of what has already been seen. But the psychologist points out that this is certainly not the only cause of the phenomenon! Many other factors could induce this appearance of familiarity and more research is being done to identify them.
Note that the scientist has also worked extensively on the alleged association between deja vu and feelings of foreboding. In fact, several people who experienced deja vu reported that they were certain of what would happen next. For Cleary, this gift of premonition is only illusory. She and her colleagues recreated deja vu conditions in the lab to test the participants’ predictive ability. The results are formal: deja vu did not lead to an ability superior to chance to predict the next turn in a navigation route that resembles a route previously experienced but not remembered “, reported the team.
However, the deja vu states were accompanied by a greater sense of knowing the direction of the next turn. As intense as it is, therefore, it is just a feeling. The team concluded that a metacognitive bias, caused by one’s own state, may explain the association between deja vu and foreboding.
And this bias is not only predictive, but also postdictive: People are more likely to think an event went as planned after it caused déjà vu. This association could be explained by the fact that a high feeling of familiarity during the development of an event falsely indicates confirmatory evidence of the fact that one always felt how that event was going to unfold.