Many people usually wonder whether Déjà vu has some sort of paranormal significance, somebody could say he saw a foreboding in a dream, another one could say he died at a checkpoint and is doing everything again. Basically, Déjà Vu is simply having seen or experienced something you're doing in the past.
|When are you getting to the next checkpoint, you're boring me already, boy.|
Scientists and psychologists have tried to link it to many things, like mental disorders and medicines. Some medicines were found to increase the rate of Déjà Vu, more specifically, those which increased dopamine activity in the brain.
|When somebody understands this, he/she explains it, but, hell, dopamine's gotta be in there somehow.|
It has been found that memory (duh) plays a huge role in this. Once a few people were given hypnosis to forget a material that they had seen. When they saw the material again, 3 of the 10 patients had what the scientists called paramnesia. Basically, they felt a great familiarity with the scene. The mechanism behind a Déjà Vu can be argued as such:
You have a memory. That memory's forgotten by you, but nevertheless stored in your brain. When you encounter the scene again, you don't remember it exactly, but you recall having seen it before, because a few certain stimulus are the same as the other one was.
Now, of course, you have people who somehow have to relate this to some sort of paranormal experience. Reincarnation and out of body experiences are the ones that most people believe can lead to Déjà Vu, which is just ridiculous. It's all in our heads, and even though it's all the less exciting, that's just it. Some sort of forgotten memory or dream that you repressed that surfaced with the stimuli. Now go back to work, this isn't some glitch in the Matrix, Neo.