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Deja vu refers to the feeling of having already experienced 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, at the beginning of the 2000s, that research provided some elements of the answer. A team of psychologists from Colorado State University has once again looked into the matter: they have managed to identify one of the factors behind this strange feeling.
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, because the phenomenon affects two thirds of the population – its frequency nevertheless decreases with age. This impression usually only lasts a few seconds and the so-called resemblance to a past experience concerns 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 to advance research on the subject. In 2003, he reviewed dozens of retrospective and prospective surveys, as well as case studies, to take stock of the knowledge acquired on the subject for more than a century. ” Deja vu seems to be associated with stress and fatigue, and it shows a positive relationship with socioeconomic level and education “, he notes 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 to a potential 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, professor of cognitive psychology at Colorado State University.
Cleary and his collaborators therefore undertook experiments aimed at testing hypotheses on 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 “shape psychology”) is a theory that perception and mental representation treat phenomena as whole shapes rather than as the juxtaposition of individual elements.
The Law of Familiarity suggests that we always perceive the most familiar and meaningful shapes. 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. Thus, the arrangement of furniture or other objects in a room could be very similar to that which you may have observed in another place in the past and thus cause deja vu.
” According to the Gestalt familiarity hypothesis, if that previous situation with a disposition similar to the current situation does not come to mind, you may only be left with a strong sense 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. They thus immersed the participants in the study in scenes created from scratch; some had exactly the same spatial arrangement, while being very distinct. As expected, deja vu was more likely to occur when people were in a scene that contained elements arranged identically to another, prior scene that they had seen but could not recall. not.
This experiment made it possible to confirm that the spatial resemblance of a new situation with a situation in memory, but which is not consciously recalled at the time, is indeed one of the factors which contribute to the appearance of an already -seen. But the psychologist points out that this is certainly not the only cause of the phenomenon! Many other factors could induce this semblance of familiarity and further research is underway to identify them.
Note that the scientist has also worked extensively on the alleged association between deja vu and feelings of premonition. Indeed, several individuals experiencing deja vu reported being sure they knew what was going to happen next. For Cleary, this gift of premonition is only illusory. She and her colleagues recreated the conditions of deja vu in the laboratory in order to test the predictive ability of the participants. The results are formal: deja vu did not lead to a greater than chance ability to predict the next turn in a navigational path resembling a previously experienced, but not recalled path “, reported the team.
However, the deja vu states were accompanied by an increased sense of knowing the direction of the next turn. As intense as it is, it is therefore only a feeling. The team concluded that a metacognitive bias, caused by the state itself, may explain the association between deja vu and the feeling of premonition.
And this bias is not only predictive, but also postdictive: people are more likely to think an event went as planned after it caused deja vu. This association could be explained by the fact that a high feeling of familiarity during the unfolding of an event falsely signals confirmatory evidence of the fact that one always felt how this event was going to unfold.