Most of us would probably agree that a good Valentine's Day should include a healthy dose of kisses and laughter. But if you think about it, both laughing and kissing are kind of strange behaviors. Why do we laugh? Why do we kiss? Are humans the only animals that giggle and smooch? And is there an evolutionary advantage to either? We'll tackle one of these mysteries in an upcoming show. As for the other, check out this article in Scientific American.