Named by psychic investigator Emile Boirac of France (1851–1917), déjà vu (which is French for “already seen”) is the feeling that a particular moment has happened before, even though the conscious mind knows that it has not. Among people who experience déjà vu, such episodes are most common during the teenage and young-adult years, but decline during the mid-twenties. However, people who travel a lot, regardless of age, tend to experience déjà vu more often than non-travellers. No one knows why this is the case.

There are many theories regarding why people have this odd sensation that an experience is repeating itself. One theory is that déjà vu occurs when a person’s mind has connected to an alternate reality in which the event that triggered the sensation really has already happened. Others theorize that the mind has connected not to an alternate reality but to memories of a previous life since they believe that, after death, a person’s soul is born again in another body. Still another theory is that the mind is connecting, through mental telepathy, to the mind of someone else who has already lived through the event in question.

A simpler explanation is that déjà vu happens when the brain connects a new experience to an old one that is similar. In other words, the new experience seems familiar because it is very like something that has happened before. Many scientists who support this view classify déjà vu as a type of illusion—specifically, an illusion of familiarity. Scientists think that déjà vu is caused by chemical changes in the brain. As evidence, they cite the fact that some people with epilepsy experience déjà vu before seizures, which result from neurochemical imbalances.

SEE ALSO: telepathy

SOURCE:

The Greenhaven Encyclopedia of Paranormal Phenomena – written by Patricia D. Netzley © 2006 Gale, a part of Cengage Learning