An old saying in teaching goes, “Good students laugh at our jokes; weak students write them down.” There is some truth there. Strong students are following our presentation well enough to distinguish between our attempts at explaining concepts and our attempts at humor. Students who are struggling with the concepts can’t follow our explanations or our humor. But there is a caution in that saying as well: We prefer to pay attention to the students who are following us, and we tend to dismiss the ones who aren’t.