In junior high school, we often told the penguin joke (about the typewriter) to test people's discernment. The joke teller would get to the punchline, and we would all bust up laughing. We tested the new-comer's courage; would he avoid peer pressure by not laughing, or perhaps admit the joke made no sense?

My one-year-old son has a similar problem. If I find something funny, he'll laugh and laugh, even if it is at a blank white wall. Human nature to conform, I guess.