Déjà vu. It’s that strange experience where you feel like a situation seems more familiar than it should be. But why do we get it?
Déjà vu is French for “already seen.” You may go to someone’s house for the first time and feel like you’ve been there before, but you’re sure you haven’t.
Young people experience déjà vu the most. Most people report their first déjà vu experience as having occurred before the age of 10, and then it tapers off as you age. This leads researchers to believe it might have something to do with brain development.
What actually causes déjà vu is still a big mystery, and there are many theories about it. But research has shown that déjà vu experiences are firmly associated with temporal-lobe epilepsy. Epilepsy is a condition that causes brain cells to send out-of-control electrical signals that affect cells around them. These haywire signals affect brain cells like dominoes, which result in a seizure wherein a person loses control of their thoughts and body movements.
Temporal lobe epilepsy in particular starts in the temporal lobe, which is the area of your brain just on top of your ears that is responsible for making and remembering memories. People with temporal lobe epilepsy frequently report having déjà vu just before they have a seizure. So, in people that do not have temporal lobe epilepsy, déjà vu could be a mini seizure that stops before it grows too large.
What’s likely happening is this: the familiar feeling you get is signaled by cells in the temporal lobe but gets ignored by other parts of the brain that check to make sure whether the signals make sense.
But it is ultimately very difficult to test déjà vu theories, as personal reports of the experience are varied. This continues to make it a very interesting topic of scientific study.