Psychology › Social psychology › Group behavior: in-groups, crowds and bystanders
The bystander effect
1964 case; 1968 study· Finding or experiment
Mixed evidenceSome support; effects smaller or less consistent than once thought.
People are less likely to help in an emergency when others are present, at least in laboratory studies.
See it on the Psychology map →What it says
The 1964 murder of Kitty Genovese in Queens was reported as watched by 38 silent witnesses; later reporting showed that claim was badly exaggerated. It still inspired John Darley and Bibb Latané. In their 1968 study, 85 percent of students who believed they alone heard a peer's seizure sought help quickly, versus 31 percent who thought four others heard it. Explanations: responsibility spreads thin, and people read others' calm as a sign nothing is wrong.
Why it matters
It changed emergency training: single out one person ('You in the red jacket, call 911') instead of shouting to a crowd.
The evidence
A 2011 meta-analysis confirmed the lab effect but found it weaker in clearly dangerous situations. A 2020 study of 219 street conflicts caught on camera found someone intervened in about 90 percent.
Open questions
In real life, larger groups make it more likely at least one person helps, so how much the lab effect matters outside the lab is debated.
Connections (2)
▸The bystander effect is a classic finding about Group behavior: in-groups, crowds and bystandersMixed evidence
The connection
The bystander effect is a classic case of groups changing individual behavior: the more people present, the less each feels personally responsible, so any one person is less likely to act. It parallels social loafing, where individuals work less hard on a team.
Who showed it and when
John Darley at New York University and Bibb Latané at Columbia, 1968; their 1970 book The Unresponsive Bystander.
How solid is it?
A 1981 review of about 50 studies and a 2011 meta-analysis of more than 7,000 participants support the lab effect.
Open questions
Real-world video shows larger groups make help from someone more likely, so the effect may describe individuals rather than whether victims get help.
▸The bystander effect shares social-cue mechanisms with Asch conformity experimentsMixed evidence
The connection
Both rest on reading other people's behavior. In Latané and Darley's smoke-filled room study, students sitting with calm actors rarely reported the smoke, much as Asch's subjects echoed actors' wrong answers. Each person takes others' inaction as evidence nothing is wrong, called pluralistic ignorance.
Who showed it and when
Latané and Darley's 1968 smoke study at Columbia University, drawing on conformity research dating to Asch's 1951 studies.
How solid is it?
In the smoke study, 75 percent of students alone reported it, versus 10 percent of those sitting with two passive actors.
Open questions
Whether bystanders are conforming to fit in, unsure what is happening, or diffusing responsibility; these mechanisms are hard to separate.