Déjà Vu is one of the most difficult situations that scientist have to study due to it’s happening without a warning. Nevertheless, there are some theories as far as it concerns the reasons that someone might experience Déjà Vu.
- Split perception: The first time you see something, you might be distracted and your brain can start forming a memory, from that glance. Therefore, you might take in more information than you actually realize. So, the next time that you see this thing, you might think that you are seeing it for the first time, when in reality your brain recalls the previous perception, and you experience déjà vu.
- Minor brain circuit malfunctions : Your brain might experience a brief electrical malfunction, that involves some sort of mix- up between the part of our brain that tracks present events and the part of your brain that recalls memories. In this way, your brain might falsely perceive what’s happening in the present as a memory, or something that already happened.
- Delayed processing: When you observe something, the information you take in through your senses is transmitted to your brain along two separate routes. If one of these routes gets the new information a little more rapidly than the other, it might lead your brain to read this single event as two different experiences.
- Memory recall: Déjà Vu can happen when you find yourself in a situation that resembles something you’ve experienced but don’t remember. It could have happened in the deep past (like your childhood), or you can’t recall it for some other reason. Even though you can’t access that memory, your brain still knows you’ve been in a similar situation and this creates an odd feeling of familiarity.
You can find more information about this here: https://www.healthline.com/health/mental-health/what-causes-deja-vu