What is prosocial behaviour?
Prosocial behaviour means any voluntary action meant to help other people. Examples: sharing food, comforting a crying friend, giving directions, donating blood, or helping a stranger who falls.
Altruism is a special kind of prosocial behaviour: helping with no thought of any reward for yourself. Most helping is a mix of caring and some reward, like feeling good or being thanked.
The opposite is antisocial behaviour, which harms others. A bystander is a person who sees something happen but is not part of it.
The bystander effect and why it happens
The bystander effect is the finding that a person is less likely to help when other people are present. Three reasons explain it:
- Diffusion of responsibility: the duty to help is spread across everyone, so each person feels only a small share.
- Pluralistic ignorance: when a situation is unclear, we look at others. If they look calm, we decide it is not an emergency, even though they are also unsure.
- Audience inhibition: we fear looking silly in front of others if we help and it turns out nothing was wrong.
Classic lab studies in the 1960s found that people who believed they were the only one hearing someone in trouble helped quickly and almost always, while those who believed others could also hear helped more slowly and less often.
Factors that change whether people help
- Number of bystanders: more people, less individual help (in unclear situations).
- Seriousness and clarity: a clear, serious emergency (screaming, blood, fire) gets more help than an unclear one.
- Cost of helping: danger, time, effort, mess or embarrassment make help less likely.
- Similarity to the victim: people help those who seem like them (age, group, clothing, team) more often.
- Competence: people with the right skill, like a nurse or a lifeguard, are more likely to step in.
- Mood and time pressure: people in a good mood help more; people in a hurry help less.
- Personality and upbringing: empathy and having seen helping modelled at home make helping more likely.
Piliavin's subway study (1969)
Aim: to see how the type of victim and their race affect helping in a real-life emergency, where people cannot easily leave.
Method: a field experiment on an express train in New York, on a part of the journey with no stops for about 7½ minutes. A male researcher (the "victim") fell to the floor about 70 seconds after the train left. In some trials he carried a cane and seemed ill; in others he smelled of alcohol and carried a bottle and seemed drunk. Victims were either Black or White. Hidden observers recorded who helped, how fast, and comments. About 4,450 passengers took part without knowing.
Results: the "ill" victim got spontaneous help in about 95% of trials; the "drunk" victim in about 50%. Help usually came fast. Most first helpers were men. There was little sign of diffusion of responsibility: bigger groups did not help less. In the drunk condition, people were slightly more likely to help someone of their own race.
Conclusion: the arousal–cost–reward model. Seeing someone in trouble makes us feel upset (arousal). We want to reduce that feeling, so we weigh the costs of helping (danger, disgust, effort) against the costs of not helping (guilt, blame). The drunk victim seemed more costly to help, so fewer people helped.
Evaluation: strong ecological validity (a real train, real reactions). But passengers could not give consent or be debriefed, and the researchers could not control who was in each carriage.
Prosocial behaviour in sport and group activities
Team games are a great place to practise prosocial skills: encouraging others, helping an injured player, sharing the ball, including quieter classmates, accepting the referee's decision and shaking hands after a match. Coaches can make helping more likely by giving each player a clear role (this beats diffusion of responsibility), praising fair play, and talking openly about how others feel.
Try it: the shared-job test
At home or in class, drop a pen "by accident" near one friend, and on another day near a group. Count how many seconds pass before someone picks it up. Then try saying a name: "Riya, could you pass that?" Notice how naming one person makes help faster. (Always tell people afterwards what you were testing.)
Key formulas and definitions
- Prosocial behaviour: any voluntary act that helps others
- Altruism: helping with no expected reward
- Bystander effect: more onlookers → less chance each one helps
- Diffusion of responsibility: duty is shared, so each feels less of it
- Pluralistic ignorance: others look calm, so we think it is not serious
- Arousal–cost–reward model: help if the cost of not helping > cost of helping
- Piliavin 1969: ill (cane) ≈ 95% helped; drunk ≈ 50% helped
Worked examples
1. A girl falls off her bicycle in a busy park. Twenty people see it but nobody moves for a minute. Use psychology to explain why.
Diffusion of responsibility: each of the 20 feels only a small share of the duty. Pluralistic ignorance: each looks at the others, sees them not acting, and decides it may not be serious.
2. In the same park, one person shouts: "You in the red jacket, please call an ambulance." Why does this work?
Naming one person removes diffusion of responsibility. That person now has the whole responsibility, so help comes quickly.
3. Use the arousal–cost–reward model to explain why fewer people helped the "drunk" victim in Piliavin's study.
Helping a drunk person seemed more costly (he might be sick, aggressive or embarrassing) and not helping seemed less costly (people may blame him for his state). So the balance pointed away from helping.
4. Give one strength and one weakness of Piliavin's study.
Strength: it happened on a real train, so the behaviour was natural (high ecological validity). Weakness: passengers did not consent and were not debriefed, which is an ethical problem.
5. A nurse on a bus helps a man who collapses, while others watch. Which factor explains this?
Competence: she has the skills and knows what to do, so the cost and uncertainty of helping are lower for her.
Common mistakes
- Saying Piliavin found a strong bystander effect. He found the opposite on the train: larger groups did not help less.
- Mixing up diffusion of responsibility (duty is shared) with pluralistic ignorance (misreading the situation from others' calm faces).
- Calling all helping "altruism". Altruism means no reward is expected; most prosocial acts bring some reward.
- Describing a study without its aim, method, results and conclusion. Exams usually want all four.