Deja Vu

I have always been interested in deja-vu's. I have deja vu quite often and it has always kind of intrigued me. I think it's quite a common thing, but I'm curious, does everyone have it quite often?

Recently it seems like I've experienced it a lot and some of them have been really long--more than a passing moment. You know, the kind where you realize that you are having deja vu, but the realization is also part of the deja vu.

I find it very interesting that I have had so many deja vu moments since I've been in China. I always thought it had something to do with things you had already experienced somehow, but this is my first time in China so it seems strange to have such vivid moments of "I've already been here and felt this".

The other day I had a "double deja vu" or "deja deja vu" (I don't know what to call it). I was riding my bike home from work and I had a deja vu moment that I had already experienced as a deja vu. I don't know if that makes any sense. It was weird. But, really cool at the same time.

If anyone knows any theories about why or how our brain does this, I'd love to hear them. It fascinates me.