Check out this NYTimes article on laughter. I consider myself a pretty hi-liarious person, but I don’t get it. I also don't get Seth McFarlane’s Family Guy, Seth McFarlane’s American Dad, and Seth McFarlane’s The Winner. What I guess I’m saying is, if I ever meet Seth McFarlane, I’m going to wind up and kick him in the nuts. Apparently, that type of thing is funny. That and ridiculous non sequiters that have nothing to do with anything except the perpetuation of illiterate fart and dick jokes. Not that I know of any literate fart jokes. I do know I once woke myself up laughing over a dream about a large Viking woman, complete with horned helmet and everything. It was so funny I got up out of bed and wrote it down so I would remember it in the morning. And in the morning I found this scrap of paper with "large Viking woman with helmet" scrawled across it, and it really wasn’t that funny.
I heard somewhere that a baby will adopt the first laugh it hears. I have no idea if that’s true, but it’s a good way to freak out new parents.