No one likes a con artist. People avoid dealing with characters who have swindled them in the past, and—according to new research—birds avoid those people, too. Ravens, known more for their intelligence, but only slightly less for their love of cheese, were trained by researchers to trade a crust of bread for a morsel of cheese with human partners. When the birds then tried to broker a trade with “fair” and “unfair” partners—some completed the trade as expected, but others took the raven’s bread and kept (and ate) the cheese—the ravens avoided the tricksters in separate trials a month later. This suggests that ravens can not only differentiate between “fair” and “unfair” individuals, but they retain that ability for at least a month, the researchers write this month in Animal Behavior. Ravens have a complex social life involving friendships and rivalries. Their ability to recognize and punish dishonest individuals, even after a single encounter, may help explain how cooperation evolved in this group of birds. For people, though, the moral of the story is simple: Be nice to ravens.