The Bystander Effect

In 1964, a young woman named Kitty Genovese was killed outside her apartment building in New York City. A newspaper reported that thirty-eight neighbors had watched or heard the attack without helping. The story shocked the public and led two psychologists, John Darley and Bibb Latané, to ask why people sometimes fail to help in an emergency.

In a famous 1968 experiment, participants took part in a discussion over an intercom. During the conversation, one speaker — actually a recording — appeared to have a medical emergency. [A] When participants believed they were the only other person listening, most quickly went for help. [B] When they believed that four others were also listening, far fewer did, and those who did help took longer. [C] Darley and Latané called this the bystander effect and suggested a cause: diffusion of responsibility. [D] When many people are present, each individual feels less personally responsible for acting.

Later investigations found that the newspaper's account of the Genovese case was inaccurate. Far fewer than thirty-eight people witnessed the attack, and at least two of them called for help. Moreover, a study published in 2019 examined real conflicts recorded by security cameras in three countries and found that in about 90 percent of cases, at least one bystander stepped in to help. The effect is real in experiments, but in real life, larger groups may also make it more likely that someone acts.