When more people are watching an emergency, everyone thinks someone else will help. This "diffusion of responsibility" can leave a victim alone in a sea of people.

We often think that if we get into trouble, being in a crowded place is safer. However, social psychology reveals a dark paradox: the more people there are, the less likely any one of them is to help. This is known as the Bystander Effect.
Psychologists Bibb Latané and John Darley identified two main reasons for this behavior:
The study of this effect began after the 1964 murder of Kitty Genovese in New York. Reportedly, dozens of neighbors heard her cries but no one intervened or called the police in time. While later reports showed some neighbors did try to help, the story sparked a massive shift in how we understand human behavior.
If you are the one who needs help in a crowd, don't just yell "Help!"
The Bystander Effect isn't about people being "evil" or "heartless." It is a psychological glitch where our brains try to pass the buck to the person next to us. Understanding this is the first step toward being the one person who actually stands up.