Most of us have at least once exclaimed in our life, 'Oh, I think I've already seen this!" When you are in a get-together with friends, at some moment you feel that you have already been in exactly similar a company some time before. Or when your teacher(usually a teacher you likes a lot) tells a particular thing in the class, you feel he/she had already told this in the class in exactly similar a context. You might have overlooked it as one among the plays of mind.(Of course it is). But did you know this phenomenon has got a name? Yes, that feel is called Deja Vu. It is a French phrase meaning 'already seen'. This term was coined by a French psychology researcher named Emile Boirac.
Although this Deja Vu has been extensively studied by many psychologists, no established theory is there to explain this phenomenon. No one has ever succeeded in reproducing this feeling in laboratory conditions either. The exponents of ESP(Extra Sensory Perception or അതീന്ദ്രിയ ജ്ഞാനം) working in parapsychology consider this as a strong evidence of extra sensory powers. Since ESP itself is something yet to be approved as areal thing, it doesn't make any difference. Many attempts have been there to link deja vu with abnormal psychology like schizophrenia, dissociative identity disorder etc and even with the anomalies of neural networks in the brain. But it has been experimentally proved that persons with some observable anomalies in the temporal lobe of cerebrum, feels deja vu very frequently.
Whatever, I have experienced this Deja Vu many times and don't know how this stuff works exactly.