IB Psychology SLTopic 3 — Group BehaviourPaper 1 & 2Core idea~9 min read
Why People Conform to a Group
Everyone in the room says the short line is the long one. You can see they are wrong. Do you say so? Most people, at least once, do not — and the reason why splits neatly into two very different motives.
📚 What you need to know
Conformity is changing your behaviour or opinion to fit in with a group.
It is often called majority influence, because people usually follow the larger group.
Minority influence — being swayed by one person or a small group — happens too, but it is less common.
Normative social influence (NSI) is conforming because you want to be liked and fear rejection. It is emotional, and it leads to compliance.
Informational social influence (ISI) is conforming because you do not know what to do and assume the group does. It is cognitive, and it leads to internalisation.
The classic study is Asch (1951), using a simple line-judging task.
Two reasons, not one
Students lose marks here by treating conformity as one thing. It is not. Two people can give the identical wrong answer for completely opposite reasons, and the difference shows up in what happens afterwards.
A quick check: if the person goes back to their old answer when nobody is around, it was normative. If they keep the new answer, it was informational.
Normative social influence in practice
NSI is about belonging. You notice that your behaviour does not match the group’s, that mismatch makes you uneasy, and you adjust. You might agree that a film was terrible when you quietly enjoyed it. Nothing about your real opinion changed — you just did not want to be the odd one out.
Informational social influence in practice
ISI is about not knowing. On your first day at a new job you copy what everyone else does at lunch, because they clearly know the routine and you do not. It is strongest when a situation is unclear, when a decision has to be made fast, or when the stakes feel high.
ISI can go badly wrong. Someone collapses in a busy street and nobody stops. Each passer-by looks at the others, sees no alarm, and concludes it must not be serious. Everyone is reading the group as a source of information, and the group is wrong.
Key study: Asch (1951)
Asch designed a task with an obvious right answer so that any wrong answer had to be caused by the group, not by difficulty.
The task was made deliberately easy. Alone, people got it right almost every time, which is what makes the conformity rate so striking.
Part of the study
What happened
Aim
To find out whether majority influence would make people give an answer they could see was wrong.
Participants
50 male students at an American university. They believed they were taking part in a vision test, so they were naive.
Procedure
The real participant sat at the end of a row with seven confederates and answered last. Each person said aloud which comparison line matched the standard. On the critical trials the confederates all gave the same wrong answer.
Results
Conformity on the critical trials was 32%. Across the whole study 74% of participants conformed at least once, and 26% never conformed at all. When there were no confederates present, errors fell below 1%.
Conclusion
People will give an answer they know is wrong rather than stand alone against a unanimous group.
The 26% figure is worth quoting. It proves conformity is not automatic — a quarter of people held out every single time, which is exactly the gap the theory struggles to explain.
Evaluating conformity research
What is strong about it
Asch’s procedure was tightly controlled. The line lengths, the number of confederates and the seating position were all kept constant, so the study is highly replicable.
The control condition, where nobody conformed, rules out the possibility that the task was simply hard.
The findings are genuinely useful: they help explain crowd behaviour at protests, and why nobody helps in an emergency.
What is weaker about it
Neither explanation covers everyone. Some people resist both NSI and ISI — whistleblowers, protesters, anyone who has ever refused to go along with the group. The theory cannot account for individual differences.
Judging lines on a card is an artificial task with no consequences. Real conformity happens where there is something to lose, so mundane realism is low.
The sample was all male and all American, giving both gender bias and culture bias.
Link to concepts
Causality: the task was so obvious that some participants may have wondered whether it was a trick. If they followed the group out of suspicion rather than social pressure, the study is measuring something other than conformity.
Bias: participants behave differently simply because they know they are in a study. Someone who conformed in Asch’s lab might never conform in ordinary life.
EXAM PRACTICE
Discuss two explanations of conformity. [22]
‘Discuss’ means present the explanations and then weigh them up. Structure beats detail here.
Opening: define conformity in one sentence
Changing behaviour or opinion to match a group, usually the majority.
Explanation 1: NSI
Wanting to be liked. Emotional. Produces compliance, so the change disappears once the group does.
Explanation 2: ISI
Wanting to be right. Cognitive. Produces internalisation, so the change lasts.
Evidence: Asch (1951)32% conformity on critical trials, 74% conformed at least once, under 1% alone. Because the answer was obvious, this points to NSI rather than ISI.
Weigh it up
Well controlled and replicable, but artificial, all-male, American, and unable to explain the 26% who never conformed.
Two explanations + one study + real evaluationUsing Asch to argue for NSI over ISI is the analysis. Do not just report the numbers.
💡 Exam tip
Tie each explanation to its outcome: NSI → compliance, ISI → internalisation. This pairing earns marks on its own.
Learn three numbers only: 32%, 74% and under 1% in the control. That is plenty.
Use the control condition as evidence. It is the strongest part of the design and most students ignore it.
The 26% who never conformed is your best evaluation point — it shows the limits of the theory.
Asch is a lab experiment. Say so, and use that word when discussing ecological validity.
⚠ Common mix-up
Swapping NSI and ISI. Normative is about norms and being accepted. Informational is about information and being correct.
Saying 32% of participants conformed. It was 32% of responses on the critical trials. 74% of participants conformed at least once.
Confusing conformity with obedience. Obedience follows an order from an authority figure. Conformity follows a group with no order given.
Confusing conformity with compliance. Compliance is one outcome of conformity, not a synonym for it.
Claiming Asch proves ISI. The task was easy and unambiguous, which points to NSI.
Up next: Cultural Dimensions and How Groups Behave — why the same line task produces very different conformity rates in Fiji and in France.
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