What is déjà vu?
Have you ever experienced déjà vu (French for 'already seen') – the feeling that something has happened before, when in fact it’s happening for the first time? Déjà vu is more common in younger people, in people with a certain form of epilepsy, and also when you are ill, tired or stressed. It may last for just a few seconds or several minutes. How your mind can fool you in this way is still a mystery, although there are several theories about it.