What is Deja vu
The phrase comes from French and means "I have seen it before". So as the phrase states, it describes the situation in which for some seconds we have the impression that a situation we are living at the moment, has happened before.
Some people happen to have this daily, some others not that often and some others rarely but everyone has had a Deja vu situation at least once in his life, it's something usual.
What causes Deja vu
Deja vu is a very complicated topic that has made many people research and think on it, especially scientists, psychologists and of course witches and philosophers. Obviously enough, the opinions vary and the explanations are many.
~Scientists, being orthologists, explain Deja vu as a temporary "crash" of the brain in which it confuses the past and present. To put this more clear, imagine your brain as a computer. Every day, hour, moment, this computer "saves" in its memory everything that happen, as "files" with dates. In its memory there are trillions of files that it recognises as old. Every "file" gets old in matters of seconds because the brain receives new data. Deja vu is a temporary crash on which the computer instead of saving the new data, it recognises it as an old file that has just been opened, hence, as a memory. So, where we should feel that something happens in the specific moment for the first time, we have the impression that it has happened in the past and we are living it again.
~Psychologists are categorised in two opinions.
The more orthologists explain deja vu as a flashback of a forgotten memory that is not exactly the same with the moment we are just living but has many common parts that woke the forgotten memory up. Let's see this with an example to make it more clear:
Let's say that some years ago you had a trip in the woods and saw a tree that you have never seen again and amused you because of its big flowers. Soon enough this moment became a memory forgotten and many years after the incidence can not recall the moment at all. So some years later you happen to be in those woods again and see a same tree like the one you saw on that day... In matters of milliseconds the brain recalls the long forgotten memory that fast that you are not able to tell the old memory with the moment you are living now. The same can happen if the tree you saw really looks like a tree you saw in a dream you have forgotten.
The second opinion is less orthologist and leaves some "back-doors" open and unexplained. Some psychologists do not reject the possibility that instinct acts prophetically in the sleeping time and expresses with dreams. So they explain Deja vu as an instant recall of a prophetic dream that has been forgotten. This opinion comes to agreement with one of the opinions of the witches.
Witches, decline the opinion of the scientists, they accept the psychologists opinion partly but the conclusion is different. Maybe we all have heard that Deja vu is a forgotten memory of a past incarnation which has been recalled because of a stimuli. (This of course presupposes that we do live more than one lives.)
Of course we can find open "back-doors" in all three theories. Personally and from all I've heard and read about people who had interesting Deja vu, I see that those theories sometimes come true and some other times really wrong. Let's see some examples:
1) Once a woman visited a house in a town she has never been before. The exact moment she stepped in the house, she felt knowing every single detail in the house's layout and rooms. The amusing thing is that that woman was right! She knew exactly where everything was, the decoration of the rooms she has not seen yet, etc. So, the scientists opinion is rejected in the first place, the psychologists can't be totally rejected although the woman insists that she has not been in the house before. The witches theory is also rejected because the house was built thirty years ago and the woman was at least in her fifties.
2) A boy in the age of seven, as the woman in the previous example
visited with his parents a castle of the middle ages in a country he has never been before. Again like the woman in the previous example, the exact moment he stepped in the central gate of the castle he seemed to know the castle with incredible details although the rooms were dozens. The boy, if we don't include some mistakes on the exact decoration of the rooms, knew where exactly each room was, perfectly. Again the scientists theory is rejected, the psychologists one rejected too since the parents of the boy say that they have never been in this castle again. So we are left with the witches theory. Now if we reject the option that we reincarnate, the case can not be explained.
3) A young girl was sitting with her friends in a park. While chit-chatting the girl suddenly says "I have lived this before, I can remember it clearly... In some minutes xx will come with a funny new hair cut!".
Indeed in some minutes "xx" came with a really funny new haircut. The girl can not explain it at all. No one knew that "xx" would come by to find them or that he just had a haircut since he decided it some hours ago. The scientists theory is rejected once again, so is the psychologists one so is the witches one. The only one that can explain it is the second theory of the psychologists that partly agree with the witches.
Looking through Deja vu's of little children we will notice that many of them can be explained by the witches theory though adults have deja vu that can be explained either by the psychologists or the scientists theory. Some teens and old people often have deja vu that accept the prophetic theory. The age of the person affects the operation of the brain and feelings, of course. Maybe it affects the Deja vu effect also? The sure thing is that every situation has to be observed individually and not collectively since all those theories can be partly accepted and partly rejected.