IB Psychology SLTopic 3 — Group BehaviourPaper 1 & 2Core idea~9 min read
Social Identity Theory Applied to Groups
Split a class in half at random, call one side red and the other blue, and within minutes the reds will think the reds are better. Nothing has happened. No one has done anything. That is how little it takes.
📚 What you need to know
Social identity theory (SIT) says part of who you think you are comes from the groups you belong to.
An ingroup is a group you belong to. An outgroup is one you do not.
Some ingroups you choose (a team, a subject class). Others you never chose at all — nationality, ethnicity, age.
Social categorisation is sorting people into groups. It is quick and uses very little mental effort, which is exactly why stereotypes form.
Social comparison is rating your group against another one, either downward or upward.
The result is ingroup favouritism, plus outgroup homogeneity — seeing them all as the same while seeing us as individuals.
The study you need is Tajfel (1972) and the minimal groups paradigm.
How the theory works
SIT breaks the process into steps. Each one is small and reasonable on its own, which is what makes the end result so unsettling.
Categorising people is genuinely useful — it saves effort. The trouble starts at the comparison step, where useful shortcuts turn into judgements.
Social categorisation
Sorting people into boxes takes almost no thought: Boomers, Italians, gamers, sixth-formers. That efficiency is the whole appeal, and it is also where stereotypes begin, because a box comes with a set of assumed contents.
Social comparison
Once you identify with a group, you start measuring it against others. Downward comparison is looking at a group you consider below yours, which protects your self-esteem. Upward comparison is looking at one above yours, which can motivate or can sting.
Outgroup homogeneity
Here is the detail that turns a theory into a warning. You see your own group as a collection of distinct individuals with different personalities. You see the other group as a lump — all the same, interchangeable, no individuality. That flattening is what makes an outgroup easy to dismiss, and, in the worst cases, easy to demonise. It is the mechanism behind propaganda that reduces a whole people to a set of ugly traits.
If you can explain outgroup homogeneity properly, you can explain prejudice, and that is worth serious marks. Most students stop at ‘people prefer their own group’ and never get to the interesting part.
Key study: Tajfel (1972)
Tajfel wanted to know the absolute minimum needed to trigger group loyalty. So he built groups that meant nothing at all.
Part of the study
What happened
Aim
To test whether preference for the ingroup appears even in groups with no real basis, using the minimal groups paradigm.
Participants
48 boys aged 14 to 15, all from the same state school in Bristol, UK.
Procedure
The boys viewed slides of paintings by Klee and Kandinsky and said which they preferred. They were told their group was based on that preference — it was not; allocation was random. They never met their group members and knew others only by a code number showing ingroup or outgroup. Alone in a cubicle, each boy allocated virtual money to two other participants using different strategies: maximum joint profit, maximum ingroup profit, or maximum difference between the groups.
Results
The boys favoured ingroup members and penalised the outgroup. Strikingly, they often chose the option that maximised the gap between the groups, even when a different choice would have earned their own group more overall.
Conclusion
Ingroup favouritism appears with no shared history, no contact and no real basis for the group. Knowing that a rival group exists is enough.
The finding that matters most. They gave up money for their own group in order to widen the gap. That is not simple loyalty — beating the outgroup mattered more than benefiting the ingroup. Make this point in an essay and you are analysing rather than describing.
Evaluating the theory
What is strong about it
SIT gives a clear framework for how people sort themselves and others, and it applies well beyond the lab.
It has real practical value — interventions against racism, bullying and other group-based behaviour draw directly on it.
In Tajfel’s design the boys never saw each other, so appearance and personality could not have influenced their choices. That removes an obvious confounding variable and increases validity.
What is weaker about it
SIT over-emphasises group membership. People have agency; they are not simply pushed around by whichever group they happen to be in.
There was no jeopardy in Tajfel’s task. Handing out points to strangers you will never meet is nothing like a real decision with real consequences, so ecological validity is low.
The sample was 48 boys of the same age from one school in one city. That is narrow.
Link to concepts
Causality: the theory is vague. It says people categorise on superficial criteria such as age or job, which is anecdotally obvious but hard to test precisely. People are complex, and labelling them as if they were jars on a shelf misses most of what is going on.
Bias: the boys may have worked out what response was wanted. Fourteen-year-olds are well practised at giving adults the answer they seem to be after, so participant expectation could explain part of the result.
EXAM PRACTICE
Evaluate social identity theory with reference to one study. [22]
Step 1: outline the theory
Identity partly comes from group membership: categorisation, then identification, then comparison, producing ingroup favouritism.
Step 2: describe the study
Tajfel (1972). 48 boys, minimal groups based on a fake painting preference, virtual money allocated in isolation.
Step 3: the key result
Boys chose maximum difference over maximum joint profit — widening the gap mattered more than gaining.
Step 4: strengths
No contact between boys removes appearance and personality as confounds. The theory explains prejudice and informs anti-bullying work.
Step 5: limitations
No jeopardy, narrow sample, possible participant expectation, and the theory downplays personal agency.
Theory + study + result + strengths + limitationsEvaluate the theory as well as the study. Questions on SIT usually want both.
💡 Exam tip
Always say minimal groups paradigm. It is the term the mark scheme looks for.
The maximum-difference finding is the single most quotable result in this topic.
Bring in outgroup homogeneity when a question mentions prejudice, stereotyping or discrimination.
Point out that the boys were told their group was based on painting preference when it was actually random. That deception is central to the design.
Link back to cultural dimensions if you can — the strength of ingroup loyalty is not identical everywhere.
⚠ Common mix-up
Saying the groups were based on real preferences. They were not. Allocation was random and the boys were misled.
Confusing the three steps. Categorisation is sorting, identification is joining, comparison is ranking. In that order.
Getting homogeneity backwards. The outgroup is seen as all the same. The ingroup is seen as full of individuals.
Saying the boys met each other. There was no face-to-face contact at any point.
Confusing SIT with social learning theory. SIT is about identity and belonging; SLT is about copying what you watch.
Up next: Social Learning Theory Applied to Groups — how a group teaches its norms without ever explaining them, and what happened when children watched an adult attack a doll.
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