The Modern Bystander Effect

The failure of bystanders to report violence being livestreamed across social media is often blamed on the medium itself, but two social psychologists came up with a better explanation more than 50 years ago.

In the 1960s, John Darley and Bibb Latane were fascinated by the killing of Kitty Genovese in the Kew Gardens neighborhood of Queens. One night in March 1964, Ms. Genovese, 28, was sexually assaulted and stabbed to death while she was on her way home from work. There were reports that some 38 witnesses did nothing to stop the killing.

That, at least, was the front-page story in The New York Times two weeks after the crime. The apparent apathy and moral inaction of so many law-abiding citizens sent shock waves across the nation.

Darley and Latane wondered if there was more to the story. They conducted a series of experiments that led them to discover the bystander effect, the theory that the more witnesses to an event, the less likely it is that any one of them will intervene, in the expectation that someone else has already responded, or will.

Over the years, evidence has emerged that the Times story was innacurate. Two neighbors had, in fact, called the police. While dozens of people nearby heard Ms. Genovese’s screams, only a few saw the attack take place.

But the bystander effect has held up in other experiments and is still covered in textbooks, continuing to provide a critical insight into human behavior in the digital age.