ABSTRACT
Imagine yourself slipping into a lecture hall just as the bell is ringing. As you take a seat, you notice with relief that the professor is running late today too—she's just finishing a chocolate bar and looking through a folder for her notes. As she begins lecturing, you notice she has a huge smear of chocolate across one side of her face. You laugh a little and turn to see if your neighbor has noticed. As you look around, it seems just about everyone has noticed except the professor, and as she moves closer to the front row, a hushed ripple of whispers and nervous laughter runs through the class. You wonder why none of the teaching assistants are doing anything to get the professor's attention. You feel sorry for her but you're also finding it very distracting. Finally, someone raises a hand and says, “Excuse me, professor, but I think you might have a little bit of something on your face.” At first, everyone is completely silent, and then the class bursts into laughter and chatter as the professor wipes her face with a tissue.
