Half a century of work says the more bystanders present at an emergency, the less likely any one of them helps. Recent meta-analytic evidence questioned whether that carries over to violent emergencies, where some argued the effect reverses. A separate line of research points elsewhere entirely, to who knows whom. Liebst and colleagues went to the surveillance tapes.
Both factors mattered, and the classical pattern held. Across eighty-one violent incidents recorded by cameras in Copenhagen, the probability of intervention fell as the number of bystanders rose, not the reverse. Pre-existing between bystanders and the people fighting also predicted intervention, and that effect was larger in magnitude than the effect of crowd size.
The starting claim is old and solid. In the presence of others, a bystander is less likely to intervene when they witness someone in need of help. This comes from Darley and Latane, it is among the most well-established findings in psychology, and it is generally read as a diffusion of responsibility.
Two complications had arisen. Recent meta-analytic evidence raised doubts about whether the effect generalizes to violent emergencies, with some expecting it to reverse when the stakes are high enough. Meanwhile a separate line of research argued that what matters is not the headcount but pre-existing social relations between bystanders and the people in the conflict.
This study compares both in real violence. The team systematically observed seven hundred and sixty-four bystanders across eighty-one violent incidents recorded by in Copenhagen. They sampled with a , coded behavior from the footage, and estimated the probability of intervention with multilevel regression.
The social relations prediction was confirmed. The reversal was not: bystanders were less likely to intervene as bystander presence increased, which is the classical effect rather than the expected inversion of it. The effect of social relations on intervention was larger in magnitude than the effect of the number of bystanders. The authors weigh that against current discussion of group size and relationships in human helping. They also make a case for video data as a way to study the question at all.
wat. A bigger crowd still means less help. But knowing the people involved mattered more than how many were watching.
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The question had been argued mostly from laboratory setups and from one misreported murder. This is real violence, on video, with the bystanders counted.
How do we know?
Researchers systematically observed and coded the behavior of seven hundred and sixty-four bystanders across eighty-one violent incidents captured by surveillance cameras in Copenhagen, sampled with a case-control design, and estimated intervention probability with multilevel regression.
What is still unknown
Observational data from one city, with relationships inferred from what the cameras show. A case-control design and regression can establish association, not why a given person moved or stayed.
Learn something?
Where to next
What did the neighbors of the most famous murder in New York actually do?bystander effect
If you were attacked in the street, would anybody actually step in?helping
Does a society get less generous when it loses an hour of sleep?helping