"If, by chance, you are served an unusually large slice of pizza, compared with what others appear to be getting, would that experience incline you, some minutes later, to eat more cookies or fewer when platefuls came your way? That depends, it turns out, on whether you are on a diet. Those who are not eat fewer cookies, whereas those who are see the excessive pizza as a licence to pig out. It is a demonstration of what Janet Polivy, a psychologist at the University of Toronto, refers to as the 'what the hell' effect—a phenomenon familiar from real life to which Dr Polivy has given scientific respectability, most recently in a paper published in the latest edition of Appetite."