Déjà vu (pronounced ; French "already seen"; also called "paramnesia," from Greek παρα "para," "near" + μνήμη "mnēmē," "memory") is the experience of feeling sure that one has witnessed or experienced a new situation previously (an individual feels as though an event has already happened or has happened in the near past). The term was coined by a French psychic researcher, Émile Boirac (1851–1917) in his book "L'Avenir des sciences psychiques" ("The Future of Psychic Sciences"), which expanded upon an essay he wrote while an undergraduate. The experience of déjà vu is usually accompanied by a compelling sense of familiarity, and also a sense of "eeriness," "strangeness," or "weirdness," The "previous" experience is most frequently attributed to a dream, although in some cases there is a firm sense that the experience "genuinely happened" in the past.

The experience of déjà vu seems to be quite common among adults and children alike; in formal studies, 70% of people report having experienced it at least once. References to the experience of déjà vu are also found in literature of the past, indicating it is not a new phenomenon. It has been extremely difficult to evoke the déjà vu experience in laboratory settings, therefore making it a subject of few empirical studies. Recently, researchers have found ways to recreate this sensation using hypnosis.

Types of déjà vu

According to Arthur Funkhouser there are three major types of déjà vu.

Déjà vécu

Déjà vécu refers to an experience involving more than just sight, which is why labeling it as "déjà vu" is usually inaccurate. The sense involves a great amount of detail, sensing that everything is just as it was before and a weird knowledge of what is going to be said or happen next.

Translated literally as "already lived," déjà vécu is described in a quotation from Charles Dickens:

When most people speak of déjà vu, they are actually experiencing déjà vécu. Surveys have revealed that as much as 70% of the population have had these experiences, usually between ages 15 to 25Howstuffworks "What is déjà vu?, when the mind is still subject to noticing the change in environment. The experience is usually related to a very ordinary event, but it is so striking that it is remembered for several years afterwards.

More recently, the term déjà vécu has been used to describe very intense and persistent feelings of a déjà vu type, which occur as part of a memory disorder.

Déjà senti

This phenomenon specifies something "already felt." Unlike the implied precognition of déjà vécu, déjà senti is primarily or even exclusively a mental happening, has no precognitive aspects, and rarely if ever remains in the afflicted person's memory afterward.

Dr. John Hughlings Jackson recorded the words of one of his patients who suffered from temporal lobe or psychomotor epilepsy in an 1888 paper: