Bystander Behaviour and Piliavin's Study
What Is Bystander Behaviour?
Bystander behaviour refers to how witnesses respond when someone needs help in an emergency. Research reveals a surprising finding: the more people who witness an emergency, the less likely any one person is to help. This is called the diffusion of responsibility — each bystander assumes someone else will act, so no one does.
Psychologists study bystander behaviour to understand what factors increase or decrease the chance that someone will step in. Two categories of factors matter: social factors (features of the situation) and dispositional factors (features of the individual bystander).
Social Factors Affecting Bystander Intervention
The presence of other bystanders reduces the likelihood of intervention through diffusion of responsibility. When many people are watching, each individual feels less personally responsible for helping. Everyone assumes someone else will take action. Additionally, people look to others to decide how to interpret an ambiguous situation — if nobody else is reacting with alarm, bystanders assume there is no real emergency.
Bystanders weigh the cost of helping against the cost of not helping. High costs of helping — such as personal danger, loss of time, embarrassment, or effort — reduce intervention. Low costs of helping increase the chance someone will step in. For example, directing someone to call emergency services is a low-cost action that is more likely to be done than physically restraining a dangerous person.
Dispositional Factors Affecting Bystander Intervention
Dispositional factors are individual characteristics that make a person more or less likely to help in an emergency.
Similarity to the victim is one key dispositional factor. Research shows that bystanders are more likely to help someone who is similar to themselves — for example, someone of the same race, age group, or social background. Perceived similarity creates empathy and a sense of shared identity, making non-intervention feel more uncomfortable.
Expertise is the other key dispositional factor. A person with relevant skills — such as a trained first-aider, nurse or police officer — is more likely to intervene because they feel competent to help. Without expertise, a bystander may feel that helping would do more harm than good, increasing the cost of intervention and making inaction more likely.
Social factors reducing bystander intervention include the presence of others (diffusion of responsibility) and high cost of helping. Dispositional factors increasing intervention include similarity to the victim and relevant expertise.
Piliavin’s Subway Study
Piliavin and colleagues conducted a famous field experiment to investigate bystander behaviour in a real-life setting.
Aim: Piliavin aimed to investigate the effect of victim characteristics on bystander behaviour in a naturalistic environment.
Method: The study took place on the New York subway. A confederate (actor) would collapse in a train carriage. In some conditions the victim appeared drunk (carrying a bottle of alcohol in a brown paper bag and smelling of alcohol); in others they appeared ill (carrying a black walking cane). The researchers observed how quickly and how often passengers helped, and recorded the race of the helper and the victim.
Results: The victim who appeared ill received help in approximately 95% of trials, typically within 70 seconds; the victim who appeared drunk received help in approximately 50% of trials. Help was typically given by someone of the same race as the victim. As more time passed without anyone helping, passengers were more likely to leave the carriage rather than assist.
Conclusion: Piliavin concluded that bystanders make a cost-benefit calculation — they are more willing to help when the cost is low (victim is ill, not dangerous) and when they perceive similarity to the victim. The study supports the view that bystander behaviour is influenced by both the characteristics of the victim and the perceived costs of helping.
In Piliavin’s subway study, the ill-appearing victim received help faster and more frequently than the drunk-appearing victim. Help was usually given by someone of the same race as the victim — supporting the role of similarity and cost in bystander decisions.
Evaluating Piliavin’s Study
A major strength of Piliavin’s study is its high ecological validity. Because it took place on a real subway with real passengers who did not know they were being observed, the findings reflect genuine behaviour in an everyday setting. This is a significant advantage over laboratory studies of helping behaviour.
However, the study raises ethical concerns. Participants did not consent to taking part, could not withdraw, and may have experienced distress watching a person collapse. Deliberately creating a distressing situation in public without consent would not be approved by modern ethical guidelines. The study is also limited to a specific urban setting and may not generalise to different cultural contexts or types of emergency.
Research on bystander behaviour also has practical applications. Knowing that diffusion of responsibility reduces helping, public safety campaigns can explicitly tell bystanders that they personally should act rather than assuming someone else will. Increasing the perceived similarity between potential helpers and those in need — for example, emphasising a shared community identity — may also raise the chance that help is offered.