Interesting question. I really don't know!
TheBigDog had a
thread on tickling that touched on some thoughts, but laughter... hmmm. Curious.
I used to wonder why it was funny to me when somebody fell down. I was a kid, and couldn't contain myself when somebody fell down the stairs! I hated myself for this response, but it was so powerful. I'll need to chew on this for a while.
