In 1964, Kitty Genovese was attacked and murdered outside her New York apartment. Initial news reports claimed 38 neighbors witnessed the attack over 35 minutes and no one called police. The story triggered intense research into why people fail to help in emergencies.

Darley and Latané's Experiment

Researchers placed participants in rooms and staged an emergency (a confederate having a seizure over intercom). When participants believed they were the only witness, 85% helped. When they believed five others also heard, only 31% helped.

The Two Mechanisms

• Diffusion of responsibility: The more people present, the less personal responsibility any individual feels
• Pluralistic ignorance: Everyone looks at others' calm reactions and concludes it must not be an emergency

The Genovese Caveat

The original story was significantly exaggerated — subsequent research found far fewer witnesses and that some did call police. But the psychological phenomenon it inspired is entirely real and well-documented.

Override

In an emergency, point at a specific person: "You in the red jacket — call 911." Direct assignment eliminates diffusion of responsibility.

Reference:

Wikipedia: Bystander Effect

https://en.wikipedia.org/wiki/Murder_of_Kitty_Genovese