Have you ever been overwhelmed by a sense of familiarity, stopping dead in your tracks with surety that you’ve experienced that exact moment before? A sense of recurrence can feel jarring, perhaps a little bit uncomfortable, because it doesn’t quite compute in our minds to repeat experiences exactly as we’ve experienced them before — it doesn’t make sense. Because was the f*ck is déjà vù really, and why does it happen?
CNN Health reports, based on this essay, that the term déjà vù is a French term for ‘already seen’ and one of a group of related quirks of memory. “Research from 50 different surveys suggests that around two-thirds of healthy people have experienced déjà vu at one time or another. For the majority, it is dismissed as a curiosity or a mildly interesting cognitive illusion.”
Déjà vù is instantaneous and fleeting and, when you experience it, you know it isn’t real. On encountering déjà vu, the brain runs a sort of sense check, searching for objective evidence of the prior experience and then disregarding it as the illusion that it is. Déjà vù experiences can be so transitory and short-lived that they are almost impossible to recreate in clinical conditions.
The Causes of Déjà Vù
In his book The Déjà Vu Experience, Professor Alan S Brown offers 30 different explanations for déjà vu. According to him, any one alone may be enough to trigger a déjà experience. As well as a biological dysfunction like epilepsy, Brown writes that stress or tiredness could cause déjà vu.
Brown is also a proponent of what is called the divided perception theory. First described in the 1930s by Dr Edward Bradford Titchener, divided perception refers to the times when the brain isn’t quite paying enough attention to its surroundings.
Another common explanation was one offered by a doctor working at the Boston veterans’ hospital. In 1963 Robert Efron suggested that déjà vu could be caused by a sort of processing error: he believed that brains were responsible for assimilating events through the temporal lobe before then adding a sort of timestamp to them to determine when they happened.
Efron saw déjà vu as resulting from the lag between seeing and adding that timestamp: if the process took too long, the brain would think that an event had already happened.
But Alan Brown and Chris Moulin both agree that the way that the hippocampus indexes memories by cross-referencing them according to familiarity is a more likely cause of déjà vu.
In other words, your brain files memories into categories by quickly referencing other memories with similar qualities, and makes you feel like the memory is being repeated — because one memory is so similar to another(s).
Interestingly, Wealthy People Experience Déjà Vù More Often
Brown suggests that although déjà vu occurs equally in women and men, it is more common in younger people, those that are well-travelled, earn higher incomes and whose political and social outlooks are more aligned to the liberal.
“People who travel more have more opportunities to encounter a new setting that they may find strangely familiar. People with liberal beliefs may be more likely to admit to having unusual mental experiences and willing to figure them out. A conservative mindset would likely avoid admitting to having strange mental events, as they might be seen as a sign that they are unstable.”
The author of this story experiences déjà vù so often it’s become a burden, partially due to the fact that it’s made everyday experiences feel more mundane because he already knows what’s going to happen.
“The shock of repeated déjà vu isn’t physical, necessarily, but instead causes a kind of psychic pain that can feel physically sickening. Dream images suddenly interrupt normal thoughts. Conversations seem to have already taken place. Even banal things like making a cup of tea or reading a particular newspaper headline seem familiar. It feels occasionally like I’m flicking through a photo album containing nothing but the same picture reproduced endlessly.”
How would you enjoy life if it felt like everything had already happened before, and you couldn’t tell what was real or not?
Read more about déjà vu here.