The more people who witness an emergency, the less likely any one of them helps
After the 1964 murder of Kitty Genovese was reported, inaccurately, as having been witnessed by 38 passive neighbours, psychologists John Darley and Bibb Latané ran experiments showing bystanders are genuinely slower to help when more people are present, each assuming someone else will act or taking cues from others' inaction. The effect has been replicated across dozens of studies with strangers staging fake emergencies.