If we speak precisely, then déjà vu is a state where a person feels that they already were in a similar situation in the past.
Moreover, this feeling doesn’t refer to any particular time. The state during déjà vu is similar to the feeling when re-reading a book or repeating a movie which one has seen a long time ago. Then, is it is possible to remember what specifically will happen in this moment and the feeling experienced can be very vivid and expressive.
Almost every person knows the feeling when it seems that they know exactly all the circumstances in which they are in during this moment. You may have said something, done some action like writing, talking or swimming. Events are likely to be experienced again and again and people like to understand what can happen in an instant. The essence of the effect of that situation, which is called the déjà vu effect, may occur when a person recalls an unfamiliar person or an unknown environment which never was.
The first scientific researcher who began to consider this unusual effect – a specialist in psychology from France Émile L. Boirac did not pass by the study of the condition and Sigmund Freud called déjà vu an amazing condition and explained it by the fact that every person has their fantasies and unconscious desires. He played against Carl Jung, who totally believed he lived in parallel universes.
Past theories are limited and in order to explain this phenomenon, they simply can’t. Nevertheless, modern scientists know the answer to this question. It is no secret that the ability to explain this phenomenon appears only in research, but not registered individual facts. Alas, but such research are not yet carried out.
Modern psychiatry says déjà vu is a specific mental disorder, which is often experienced during hallucinations. It is known that this condition appears much more frequently in people who suffer from brain diseases, often experienced by epileptics. Doctors say that this effect is associated with memory disorders. Statistics says that the déjà vu effect is at least once in a lifetime is experienced by 97 % of normal healthy people. That is, the brain perceives what is happening at the same time as the past, and as the present. This is because there is a sense of separation from reality. We can say that the occurrence déjà vu is not nothing wrong.
This is not a disorder of the brain, or perception. But, nevertheless, this phenomenon is still too little studied, but for a long time it will generate interest, or even fear of the unknown.