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The term déjà vu (French: "already seen", also called paramnesia) describes the experience of feeling that one has witnessed or experienced a new situation previously. The term was created by a French psychic researcher, Emile 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 French concentrator at the University of Chicago. The experience of déjà vu is usually accompanied by a compelling sense of familiarity, and also a sense of "eerieness," "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 very common; in formal studies 70% or more of the population 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. However, in laboratory settings, it is extremely difficult to invoke the déjà vu experience, making it a subject with few empirical studies.

Déjà vécu

Usually translated 'already seen' or 'already lived through,' déjà vécu is described in a quotation from David Copperfield by Charles Dickens:

We have all some experience of a feeling, that comes over us occasionally, of what we are saying and doing having been said and done before, in a remote time - of our having been surrounded, dim ages ago, by the same faces, objects, and circumstances - of our knowing perfectly what will be said next, as if we suddenly remember it![1]

When most people speak of déjà vu, they are actually experiencing déjà vécu. Surveys have revealed that about one third of the population have had these experiences, more often (and perhaps more intense) in people between the ages of 15 and 25. The experience is usually related to a very banal event, but is so striking that it is remembered for years afterwards.

Déjà vécu refers to an experience involving more than just sight, which is why labeling such "déjà vu" is usually inaccurate. The sense involves a great amount of detail, sensing that everything is just as it was before. Because of this, theories that the situation was just read about earlier or experienced in a previous life are invalid, as those experiences could not recreate the exact situation due to a lack of sense involvement or the presence of modern surroundings.

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. As described in Moulin, C.J.A., Conway, M.A. Thompson, R.G., James, N. & Jones, R.W. (2005). Disordered Memory Awareness: Recollective Confabulation in Two Cases of Persistent Déjà vecu. Neuropsychologia, 43 :1362-1378.

Dr. John Hughlings Jackson recorded the words of one of his patients who suffered from temporal lobe or psychomotor epilepsy in an 1889 paper:

What is occupying the attention is what has occupied it before, and indeed has been familiar, but has been for a time forgotten, and now is recovered with a slight sense of satisfaction as if it had been sought for. ... At the same time, or ... more accurately in immediate sequence, I am dimly aware that the recollection is fictitious and my state abnormal. The recollection is always started by another person's voice, or by my own verbalized thought, or by what I am reading and mentally verbalize; and I think that during the abnormal state I generally verbalize some such phrase of simple recognition as 'Oh yes - I see', 'Of course - I remember', &c., but a minute or two later I can recollect neither the words nor the verbalized thought which gave rise to the recollection. I only find strongly that they resemble what I have felt before under similar abnormal conditions.

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 afterwards.

As with Dr. Jackson's patient, some temporal-lobe epileptics may experience this phenomenon.

This experience is less common and involves an uncanny knowledge of a new place. Here one may know his or her way around in a new town or landscape while at the same time knowing that this should not be possible.

Dreams, reincarnation and also out-of-body travel have been evoked to explain this phenomenon. Additionally, some suggest that reading a detailed account of a place can result in this feeling when the locale is later visited. Two famous examples of such a situation were described by Nathaniel Hawthorne in his book Our Old Home and Sir Walter Scott in Guy Mannering. Hawthorne recognized the ruins of a castle in England and later was able to trace the sensation to a piece written about the castle by Alexander Pope two hundred years earlier.

C. G. Jung published an account of déjà visité in his 1966 paper On synchronicity.

In order to distinguish déjà visité from déjà vécu, it is important to identify the source of the feeling. Déjà vécu is in reference to the temporal occurrences and processes, while déjà visité has more to do with geography and spatial dimensions.

In recent years, déjà vu has been subjected to serious psychological and neurophysiological research. The most likely candidate for explanation, according to scientists in these fields, is that déjà vu is not an act of "precognition" or "prophecy" but is actually an anomaly of memory; it is the impression that an experience is "being recalled" which is false. This is substantiated to an extent by the fact that in most cases the sense of "recollection" at the time is strong, but any circumstances of the "previous" experience (when, where and how the earlier experience occurred) are quite uncertain. Likewise, as time passes, subjects can exhibit a strong recollection of having the "unsettling" experience of déjà vu itself, but little to no recollection of the specifics of the event(s) or circumstances they were "remembering" when they had the déjà vu experience, and in particular, this may result from an overlap between the neurological systems responsible for short-term memory (events which are perceived as being in the present) and those responsible for long-term memory (events which are perceived as being in the past).