The bystander effect occurs when people within a group witness an incident but do not take action to interfere due to the presence of other bystanders.

The bystander effect is a theory that emerged in the late 1960s. It suggests that onlookers will become less likely to help a person in need if other people are present.

People may freeze, become apathetic, avoid a plea for help, or ignore an emergency in the presence of other onlookers or bystanders.

This article explores the bystander effect, including what may cause it, real-life examples, and how to prevent becoming a bystander when witnessing an incident that may require intervention.

Content warning: This article contains details of a violent crime that people may find upsetting.

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Researchers coined the term “the bystander effect” following the violent attack and murder of a woman named Catherine “Kitty” Genovese.

The crime occurred over approximately 30 minutes. During this time, 38 neighbors heard Kitty’s cries for help, but no one called the police.

Although the incident became global news, the American Psychological Association (APA) suggests that similar incidents with inactive witnesses likely occur daily.

A 2018 article references an older research program from the 1960s that examined the diffusion of responsibility during emergencies.

The 2018 article summarizes the findings, suggesting that a lone witness would offer help, but only 62% of people would intervene when they were part of a group of five bystanders.

A 2019 article suggests the bystander effect may occur because of the interdependence between groups of people.

The article’s authors suggest people in a group may expect someone else to help, which relieves them of the responsibility to take action.

Even if they think no one else will help, the blame for inaction applies to everyone in the group, which may lessen feelings of guilt.

Another 2018 article suggests three main psychological factors that may lead to the bystander effect:

  • Diffusion of responsibility: People may feel a shared responsibility when in a larger group, so individuals may not take action because they feel less responsibility when others are present.
  • Evaluation apprehension: People may fear unfavorable judgment from others around them if they take action.
  • Pluralistic ignorance: Pluralistic ignorance is a mistaken belief that others in a group think differently from how they do. If nobody else is taking action, a bystander may believe the situation is not an emergency.

Bullying can involve bystanders, who may or may not take action to stand up against the behavior. Bystanders in bullying incidents may take on various roles, including:

  • passive supporters, who witness the incident but do nothing to interfere
  • possible defenders, who want to intervene but are unsure how to do so
  • supporters, who encourage or respond positively to the bullying behavior
  • defenders, who may tell the bully to stop

A 2019 article suggests the bystander effect may also occur at work. People may stay silent and avoid speaking up to voice concerns, ideas, or opinions relating to their work.

Employees may be aware of certain information, but employers may not be. If information spreads among employees, an individual may be reluctant to step forward and voice the information to a manager.

As the Kitty Genovese incident shows, the bystander effect may also occur during criminal or violent acts if an incident occurs in the presence of others.

A 2022 study looked at the effect of danger on whether bystanders were more or less likely to intervene and help someone. The study found that bystanders were 19 times more likely to intervene if they witnessed incidents involving targeted aggression.

This may be due to an increased sense of urgency or potential feelings of safety in the presence of other witnesses. Further research is necessary to understand whether the intensity of danger affects a bystander’s likeliness to intervene.

A 2018 article suggests that personality traits, such as sympathy, compassion, and personal distress, may influence whether a bystander is more likely to help.

In incidents with a higher number of bystanders, there is a link between personal distress and a decrease in helping, whereas sympathy did not. Focusing on others needing help, rather than the self, may influence the bystander effect.

Whether people in a group of bystanders know each other or not may also influence whether people help. Bystander inaction may decrease if the bystanders know each other. However, the 2018 article’s authors stress the need for further research.

The APA recommends the following tips for intervening in a bystander situation:

  • being aware of discriminatory or emergency situations
  • assuming responsibility for taking action
  • deciding how best to intervene
  • taking action

People can memorize the five D’s for intervening as a bystander:

  • Distract: Try to diffuse the situation or cause a distraction, such as making a commotion or engaging a person in small talk to disrupt the harassment.
  • Delegate: Ask for help in intervening, ideally from a person of authority. In an emergency, people should call 911.
  • Document: If it is safe to do so, and if the person in need is receiving help, take a video or photo, or write notes on the situation and people involved.
  • Delay: If possible, check in with the person who is the target of the incident and offer assistance or support.
  • Direct: If the target of the incident and everyone else is safe, speak out against the harasser and their behavior.

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The bystander effect is the theory that people are less likely to help someone in need if others are present. This behavior can occur when groups of people witness crimes, violence, or bullying.

It may occur because people perceive themselves as having less responsibility in group settings, fear judgment, or believe that a situation cannot be an emergency if no one else is attempting to help.

To prevent the bystander effect, if people are in a group and witness an incident, individuals should assume responsibility and take action.