Howdy all,
I friend recently put me onto this site and i saw cecils write up on de ja vu and i thought i’d add my 2 cents as i came up with my own theory (which i’m sure there are many).
A friend was recently telling me of how he saw this documentary on the human brain and its memory function. He described a few of the experiments that seems to indicate that the human brain reads from it memory banks in familier situations.
One of the experiment was where brain wave activity was monitored when picuters were shown to the subjects. When a unfamiler picture was shown to a subject there was brainwave activity in a part of the brain responsible for analysis. However when a familier picture was show (say of their bedroom, kitchen etc…) there was brain activity in the memory part of the brain but little activity elsewhere.
Another of the experiments which was quite amusing was one where they got people to do a deposit with a bank teller. While the bank teller was doing his/her work the bank teller would bend down under the counter to get something and a different person would come back up and continue the payment. The tellers were dressed the same but had different facial features. After making the deposit people were asked if that noticed anything when doing the deposit. And practically all of the people said they didn’t.
So what the scientist theorised from all this was the that the brain uses its memory in familier situations instead of doing excess work in processing the information.
So from this i was able to make a theory for de ja vu. For me i usually get de ja vu when i’m doing familier activites like taking the dog for a walk or speaking to a friend or anything like that. So what i thought was that in these familier circumstances the brain is using the memory of past event to paint a picture of current events. And in this process the brain and your consciousness get their wires crossed and you get that feeling where you think you’ve been here before or your simply reliving past occurances (which is basically true).
Pretty nice and neat theory 
, i’m sure its full of holes i can’t see but i like it all the same
orfeo