Again, as a horror writer, I’m interested in human psychology and how individuals and groups respond to crisis. This interesting short documentary describes the Bystander Effect. Basically, it means that groups of people are less likely than individuals to act to help others in an emergency. Imagine a zombie attacking and eating somebody in a public place, and a crowd of people standing around watching, screaming at everybody else to do something.
The Asch Experiment shows that people will change their behavior to fit in with with other people, suggesting that humans have a conformist, herd instinct.