 Humor, like other play, sometimes takes the form of activity that would not be mistaken for serious activity. Wearing a red clown nose and making up nonsense syllables are examples. More often, however, as in the conversational moves above, humor and play are modeled on serious activities. When in conversation we switch from serious discussion to making funny comments, for example, we keep the same vocabulary and grammar, and our sentences transcribed to paper might look like bona-fide assertions, questions, etc. This similarity between non-serious and serious language and actions calls for ways that participants can distinguish between the two. Ethologists call these ways “play signals.” 