[abeppu]

I think even if laughter is something we have in common with lots of animals, humour still seems rather special to me. Laughing when tickled doesn't clearly indicate anything special is going on, but constructing and telling a joke requires not just language at the level of a structured system of symbols carrying meaning, but also a kind of counterfactual theory of mind. A humorist understands and manipulates expectations in order to violate them in a nonthreatening manner.