Deja vu

Well one explanation I heard is that Deja vu is (as I remember) a mix up between your long and short term memories. When it happens your long term memory kicks in before your short term does and it then seems to you like you have been here before. I am not totally sold on that explanation 'cause back in the 70s I had a Deja vu that afterwards I was convinced that I experienced it months before in a dream. But as they say, "if you can remember the 70s you didn't live through them) ;- }