Have you ever paused in the middle of a conversation or an activity, looking around, only to be hit by an overwhelming sense of familiarity when even though you’re sure you haven’t been in the situation? Probably most of us have been through that. This experience is called ‘Déjà Vu.’ The word, literally translated from French, means “already seen” and is a ubiquitous experience: almost 97% of people are thought to have experienced it at least once.
Déjà Vu shouldn’t be confused with familiarity– the feeling of walking through the same route and recognizing the scenery is familiarity, while Déjà Vu is when you feel like you’ve experienced the scenario in the past, even though you know that it hasn’t happened.
This sensation is almost impossible to study, and there are many theories explaining the cause of Déjà Vu. The following are some of the more prominent theories regarding this experience:
1. The theory of split perception explains that déjà vu happens when you see the same thing twice. They might’ve been distracted the first time or their vision was obscured. When they perceive the scene for the second time immediately after the first time, they’re consciously experiencing it. It feels like two different events because it was partially processed the first time. Since it correctly didn’t enter your perception the first time, it feels like two separate events.
2. Another hypothesis suggests that excessive amounts of dopamine may cause experiences of déjà vu. A case study has been written about an instance: a man who took a combination of flu medicines (amantadine and Proin) to treat an infection. He reported that he began experiencing many episodes of déjà vu —and they stopped when he stopped using those medications. These medicines work on the dopamine system to reduce the symptoms of the flu. Hence, it is thought that déjà vu episodes can be caused by excess dopamine in the system.
3. The more stressed or tired a person is, the more they report experiences of déjà vu. It is thought to happen because stress and fatigue affect memory (both short-term and long-term), and when one is under immense amounts of pressure and has a lot of information to process, the brain is more likely to have difficulty which leads to a ‘glitch.’
4. Déjà vu is also thought to occur when one detects familiarity during a particular event, which stimulates the rhinal cortices (which play a role in the visual memory network) but doesn’t activate the hippocampus, which helps in recalling concrete memory information. According to this explanation, this is why one feels like they’ve been there before, but they can’t pinpoint the experience.
5. The brain uses a dual processing system– a fast process involved in immediate sensation and memories, and a slower process blends past and present memories. These two processes work harmoniously, but sometimes, they might get out of sync. When this happens, the fast process happens at its usual pace while the slower process lags by a fraction of a second. Because of this slowdown, the brain is unable to decide whether the event has happened earlier in the past or not. This phenomenon is called a mismatch. The déjà vu occurs because of the memory conflict in the brain because it cannot decide whether the memory occurred before.
These are some of the most widely accepted theories as to why déjà vu occurs. Déjà vus are incredibly hard to observe and study, and these explanations take in most of the facts and try to explain everything clearly.
References:
1. Blanchfield, T. (2022, May 31). What is Déjà vu and why do we experience it?. Verywell Mind. https://www.verywellmind.com/what-is-deja-vu-why-do-we-experience-it-5272526#toc-causes-of-dj-vu
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