Imagine you’re working at a local hotel when someone hands you a lost wallet. What do you do? Would your behavior change if the wallet were full of cash? For three years, researchers studied those questions, planting 17,303 wallets in 40 countries, including the U.S. Walking into post offices, hotels, and other public places, they approached reception, and said, “I found this on the street around the corner. . . . I’m in a hurry and have to go. Can you please take care of it?” All the wallets contained business cards; some had no money while others contained at least $13.45. They expected a low return rate for wallets with cash, but results showed the opposite: People were more likely to report the lost wallets with money—and the more money, the more likely the wallets would be returned. This may be in part due to an honest desire to help other people, researchers say, but it also comes down to how we see ourselves. “The evidence suggests that people tend to care about the welfare of others,” says study author Alain Cohn at the University of Michigan, “and they have an aversion to seeing themselves as a thief.”