Most have heard of the murder of Kitty Genovese, the woman who was raped and stabbed multiple times outside of her New York City apartment in 1964. It is said that, despite cries (“Oh my God, he stabbed me! Help me!”) and multiple attacks by the perpetrator that spanned over a half hour, no one called the police. It has now been confirmed that a few neighbors tried to help: one called out “Let that girl alone!”, which prompted the attacker to leave momentarily, but he came back. Another called the police after the second attack, and another neighbor came outside to check on Genovese, who was dying and too weak to get inside. Genovese died on the way to the hospital.

This story prompted psychologists and non-experts alike to wonder, why had none of the other neighbors helped? Had the police been called immediately, she may have survived. It was confirmed that several others did witness parts of the attacks. Many believe this is an example of the Bystander Effect: people’s tendency not to help when they perceive that there are other passive witnesses. It’s a robust effect that has been shown with a variety of field and experimental situations: when passing a stranded driver on the road, when someone becomes injured, has an asthma attack, or even when someone just drops a bunch of pencils and needs help picking them up. A previous review (Latané & Nida, 1981) found that people are more likely to help if the bystander is very young (i.e., too young to help) or the situation is very unambiguous. Since these original studies, we have learned even more about this important social phenomenon.

A meta-analysis by Fischer and colleagues, published in the Psychological Bulletin in 2011, talks about some of the factors that change someone’s likelihood to help. Interestingly, they found that whether you know the bystanders can change the likelihood of intervening. If the people around are strangers, you’re less likely to intervene than if you are with friends.

In general, Fischer and colleagues concluded that people are more likely to intervene if the costs of not intervening are high (i.e., if the situation is dangerous), such as in the case of someone being physically attacked. Furthermore, if the situation requiring intervention is dangerous, the bystander effect is reversed: people become more likely to intervene when someone else is with them. The authors conclude that this is because additional bystanders in a dangerous situation are perceived as sources of physical back-up. Consistent with this idea, the bystander effect (i.e., inaction in the face of an emergency) increased when there were no male bystanders available.

Despite encouraging results that people will be more likely to intervene when danger is high, the general likelihood of anyone helping is around 70-75% when they are alone (and thus, the only one available to help), and around 50% if another person is present. The more bystanders there are, the less likely they are to help (~20% for a group).

Take Home Message:

In general, the presence of others decreases the likelihood that you will intervene when someone else needs help This effect is particularly drastic if you are amongst a group of strangers (and less so if you are with fewer people, or friends)

If the situation you witness appears clearly dangerous, you are more likely to help when the bystanders appear to be helpful for a physical intervention (i.e., if they appear physically competent, or are men)

How to Apply These Findings:

Don’t expect “someone else” to help (because it’s likely everyone else is expecting the same!)

If it is too dangerous to personally intervene, at least call the police (don’t assume someone else has or will)

Know that ambiguous situations are especially likely to go un-intervened. Consider, for example, a person slumped over on the sidewalk as bystanders walk by. Would you make sure they’re OK? Most people won’t, because it’s ambiguous: the person could just be sleeping.

Watch this video for a clear demonstration of the bystander effect:

Fischer, P., Krueger, J. I., Greitemeyer, T., Vogrincic, C., Kastenmüller, A., Frey, D., & … Kainbacher, M. (2011). The bystander-effect: A meta-analytic review on bystander intervention in dangerous and non-dangerous emergencies. Psychological Bulletin,137(4), 517-537. doi:10.1037/a0023304

Latané, B., & Nida, S. (1981). Ten years of research on group size and helping. Psychological Bulletin, 89(2), 308-324. doi:10.1037/0033-2909.89.2.308