"Subjects coming out of a phone booth encounter a woman who has just dropped some papers, which are scattered across the ground. Some subjects help pick up the paper; others do not. The difference between the two groups is largely fixed by whether a subject found a coin that the experimenter had planted in the phone booth. Those who find the coin are happy and tend to help; people who don’t find a coin tend not to help. Other experiments get similar results even when the stakes are much higher"