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Cognition and emotion in groups: groupthink, deindividuation and the bystander effect (QCE Psychology Unit 4)

Syllabus dot point

“Describe social and cognitive factors that influence individual behaviour, including groupthink, diffusion of responsibility, audience inhibition, social influence and cost-benefit analysis”

6 min read

Quick answer

Groups change individual thinking and feeling. Group polarisation pushes group decisions to extremes, and groupthink (Janis) leads cohesive groups to poor decisions by suppressing dissent. Deindividuation reduces self-awareness and accountability in crowds, social loafing reduces individual effort, and the bystander effect (Darley and Latane) means people are less likely to help when others are present.

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  1. What this dot point is asking
  2. The answer
  3. Exam-style questions
Syllabus placement

This is Unit 4 Topic 2 (Interpersonal processes) subject matter in the QCAA Psychology 2025 syllabus. Group polarisation and deindividuation, discussed below, are useful context but are not named in the 2025 syllabus; groupthink, diffusion of responsibility, audience inhibition, social influence and cost-benefit analysis are.

What this dot point is asking

QCAA wants you to explain how the presence and influence of a group changes individual cognition (decision-making) and emotion (arousal, responsibility), using named phenomena and studies. You should describe each process, explain why it occurs, and support it with evidence.

The answer

How groups change cognition

Being in a group alters how decisions are made, often making them more extreme or worse.

  • Group polarisation. Group discussion tends to strengthen the average pre-existing view, producing a more extreme decision than individuals would make alone. A cautious group becomes more cautious; a risky group becomes riskier.
  • Groupthink (Janis, 1972). In highly cohesive groups under pressure, the desire for harmony and agreement overrides realistic appraisal of alternatives. Symptoms include an illusion of invulnerability, self-censorship, pressure on dissenters and an illusion of unanimity. Janis analysed real political fiascos such as the Bay of Pigs invasion. Groupthink can be reduced by encouraging dissent, appointing a devil's advocate and seeking outside opinions.

How groups change emotion and behaviour

Groups also change arousal, accountability and effort.

  • Deindividuation. In a crowd or when anonymous, people experience reduced self-awareness and weakened personal accountability, which can release impulsive or antisocial behaviour. Zimbardo's research showed that anonymity (hoods and uniforms) increased participants' willingness to administer shocks, and the Stanford prison study illustrated how anonymity and roles can unleash aggression.
  • Social loafing. Individuals tend to exert less effort when working in a group than when working alone, because individual contributions are less identifiable. Ringelmann's rope-pulling work first demonstrated this reduction in effort.

The bystander effect

The bystander effect is the finding that the presence of other people reduces the likelihood that any individual will help in an emergency.

  • Darley and Latane (1968). Following the Kitty Genovese case, they staged emergencies and found that the more bystanders present, the less likely and the slower any individual was to help. They explained this through diffusion of responsibility (each person assumes someone else will act) and pluralistic ignorance (people look to others, who also appear calm, and conclude there is no emergency). Their five-step decision model describes the points at which helping can break down: noticing the event, interpreting it as an emergency, taking responsibility, knowing how to help and deciding to act.

Why these processes matter

These phenomena show that individual cognition and emotion are not fixed; they shift systematically with the social context. The same person may make a balanced decision alone but a reckless one in a polarised group, or help readily when alone but freeze in a crowd.

Key fact

In Darley and Latane's studies, a participant who believed they were the only witness to an emergency helped about 85 percent of the time, but this dropped to around 31 percent when they believed four others were also present. The drop is explained by diffusion of responsibility across the group.

Putting it together for an exam

Identify whether the question concerns cognition (polarisation, groupthink) or emotion and behaviour (deindividuation, loafing, bystander effect), name the process, explain its mechanism, then support it with a named study. Linking the social context to a change in the individual is the key skill.

Common traps
Confusing group polarisation and groupthink
Polarisation makes decisions more extreme; groupthink makes cohesive groups suppress dissent and reach poor decisions.
Saying the bystander effect means people are heartless
It results from diffusion of responsibility and pluralistic ignorance, not from indifference.
Mixing up deindividuation and social loafing
Deindividuation is reduced self-awareness and accountability; social loafing is reduced effort because contributions are not identifiable.
Forgetting the named studies
Use Janis for groupthink, Zimbardo for deindividuation and Darley and Latane for the bystander effect.

Exam-style questions

Questions in the style of QCAA exam questions on this dot point, each with a worked answer. They are written by ExamExplained unless tagged "Past paper"; the year shows the paper a question is modelled on.

Practice4 marks
An experiment replicated Darley and Latane's (1968) methodology. A confederate faked an epileptic seizure during an intercom group discussion of varying size. The percentage of participants who responded and the average response time (in seconds) were recorded. Identify the trend in the rate of participants responding and the trend in response time. Support your response with evidence.
Show worked answer →

Trend in rate of responding (2 marks): as group size increased, the percentage of participants who responded decreased. Evidence: the response rate was highest in the smallest group (size 2, participant and victim) and fell as more bystanders were added.

Trend in response time (2 marks): as group size increased, the average time taken to respond increased. Evidence: mean response time rose steadily from about 56 seconds with one other person present to around 170 seconds in the largest group (size 6).

Both trends illustrate the bystander effect, explained by diffusion of responsibility as the number of bystanders grows.

Practice2 marks
An experiment replicated Darley and Latane's (1968) seizure methodology, recording how bystander group size affected helping. Predict a likely change in the data if participants were drawn from a population of medical professionals. Provide a reason for your response.
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Prediction (1 mark): a higher percentage of participants would respond and average response times would be shorter (faster helping) across all group sizes.

Reason (1 mark): medical professionals have high perceived competence and relevant training for a medical emergency such as a seizure, so they feel more able and responsible to act. This reduces the inhibiting effect of diffusion of responsibility and audience inhibition, weakening the bystander effect and increasing prompt helping.

Practise this

Sources & how we know this

ExamExplained