Difficulty: Introductory | Prerequisites: None. A basic understanding of what "group behaviour" means is helpful but not required.
Social Identity Theory (SIT) sits at the heart of social psychology. It explains why people sort themselves and others into groups, and why that sorting shapes everything from playground cliques to political polarisation. The theory was developed by Henri Tajfel and later expanded with John Turner, and it underpins most exam questions on intergroup behaviour, prejudice, and conformity in introductory psychology courses. If you have covered basic concepts of the self-concept and self-esteem, you are ready for this material.
People define themselves partly through the groups they belong to. Social Identity Theory says this happens in three stages: we categorise people into groups, we identify with certain groups, and we compare our group favourably against others. Sherif's Robbers Cave experiment showed this process in action, with boys at a summer camp forming fierce group loyalties and hostilities, then cooperating only when they shared a common goal.
Social Identity Theory (SIT)
The theory, proposed by Henri Tajfel, that a person's sense of who they are is partly based on the groups they belong to. In simple terms, "I am" is partly "we are."
Social categorisation
The cognitive process of classifying people (including yourself) into groups based on shared characteristics such as religion, nationality, gender, or school. Think of it as the brain's filing system for people.
Social identification
The stage at which a person adopts the identity of a group they have categorised themselves into, gaining a sense of belonging and emotional attachment. In simple terms, you start thinking of the group's wins as your wins.
Social comparison
The process of comparing your in-group favourably against out-groups to maintain or boost self-esteem. This is the "us vs. them" stage.
In-group
The group a person identifies with and feels they belong to. Think of it as "my people."
Out-group
Any group a person does not identify with, often viewed less favourably than the in-group.
In-group favouritism (in-group bias)
The tendency to favour members of your own group over those in out-groups, even when there is no rational basis for doing so.
Salience
The degree to which a particular social identity is activated or prominent in a given context. In simple terms, whichever group membership feels most relevant right now is the salient one.
Superordinate goal
A goal that can only be achieved through cooperation between groups. This is the mechanism Sherif used to reduce hostility between groups in the Robbers Cave experiment.
Personal identity vs. social identity
Personal identity is how you see yourself as an individual (traits, preferences). Social identity is how you see yourself through the lens of group memberships. A person holds several social identities at once.
Stage 1: Social Categorisation
You cannot belong to a group unless you first recognise that the group exists
This happens through observation of the world around you, often without conscious thought
All it takes is walking into a school cafeteria: people are divided into groups by religion, nationality, ethnicity, gender, physical abilities, how they were raised, where they grew up
Groups are labelled by their characteristics, and these labels become categories the brain uses automatically
Stage 2: Social Identification
Once you know groups exist, you begin identifying with one or more of them
This includes identity categories such as gender (man, woman, non-binary), religion (Catholic, Jewish, Muslim), sexuality (straight, bisexual, homosexual), and many others
What you identify with is limitless; a person holds multiple social identities simultaneously
Identification brings a sense of emotional belonging to the group
Stage 3: Social Comparison
The final stage produces the "us vs. them" mentality
You compare your in-group to out-groups, typically viewing your own group more favourably
You compare yourself and people in your group to outsiders
This comparison tendency is described as natural to human cognition
A person does not have just one "personal self" but rather several social selves that correspond to group memberships
We come to know our value in social contexts by categorising ourselves
SIT is grounded in the cognitive process of social categorisation: classifying people into groups based on similar characteristics
Sometimes one of our social identities becomes more salient (more prominent), meaning it becomes a stronger facet of identity in that moment
Which identity is salient depends on context: a student might feel their university identity most strongly at a football match, but their national identity when travelling abroad
Sherif wanted to investigate relations between groups. Specifically: would strangers brought together into a group with common goals form a close group, and would competition between two such groups produce hostility?
22 boys, aged roughly 12, all white, American, middle-class Protestants
Participants were separated into two groups and taken to a National Park in Oklahoma
The two groups lived separately and initially did not know the other group existed
Stage 1: In-Group Formation
For five days, each group was given tasks to carry out together to help them bond
Each group was given a name, which strengthened their group identity
The groups developed their own norms and hierarchies
Stage 2: In-Group Relations / The Friction Phase
Over the next days, friction between groups was encouraged by means of competition
Groups competed against each other for different prizes
This stage was designed to create intergroup conflict
Stage 3: Inter-Group Relations / The Integration Phase
This stage was designed to reduce the tension between the groups
Participants were brought together to watch films and then to take part in joint problem-solving activities
In one activity, the water supply was blocked by "vandals" and the two groups worked together to solve it
Groups also pooled their money to free a truck
Stage 1 findings:
The boys bonded within their groups
Even before meeting the other group, they expressed dislike towards them simply upon learning of their existence
Stage 2 findings:
Competition produced open hostility
Both groups raided the other's huts and burned their flags
When together, the groups insulted each other and were close to physical violence
Each group refused to eat with the other
Prizes were stolen
Stage 3 findings:
Early activities that simply brought the groups together without competition did not reduce hostility
Joint problem-solving tasks (superordinate goals) did reduce hostility
Both groups opted to share a bus home
The Rattlers spent a $5 prize they won in one competition on drinks for both groups
Sherif's findings explain why workplace teams, sports fans, and even nations can develop fierce loyalties and rivalries with minimal provocation, and why shared goals (rather than mere contact) are needed to defuse intergroup tension. This principle underpins modern conflict-resolution and team-building strategies.
Students often think the three stages of SIT must happen slowly over time. They do not. Categorisation can happen in seconds, as Tajfel's minimal group experiments showed.
Students sometimes confuse social identity with personal identity. Social identity is specifically about group memberships, not your individual traits or preferences.
A common error is assuming that Sherif's study showed that simple contact between groups reduces hostility. It did not. Mere contact (watching films together, eating together) failed. Only superordinate goals worked.
Students often believe in-group favouritism requires a real conflict of interest. Tajfel's research showed it emerges even when groups are assigned arbitrarily (the "minimal group paradigm").
⚠️ Know all three stages of SIT (categorisation, identification, comparison) and be able to define each in one sentence
⚠️ Be able to describe Sherif's three experimental phases and what each found
⚠️ Understand why mere contact failed but superordinate goals succeeded in reducing hostility
⚠️ Be ready to distinguish between personal identity and social identity
⚠️ The concept of salience is frequently tested: which social identity is active depends on the situation
True or false: Social categorisation requires conscious, deliberate thought. (False: it happens automatically.)
Fill in the blank: The third stage of SIT is social ________. (Comparison.)
True or false: In Sherif's study, simply bringing the groups together to watch films reduced hostility. (False: only superordinate goals worked.)
Fill in the blank: When a social identity becomes especially relevant in a given context, we say it has become more ________. (Salient.)
True or false: A person has only one social identity at any given time. (False: people hold multiple social identities simultaneously.)
Q: Name and briefly define the three stages of Social Identity Theory.
A: (1) Social categorisation: classifying people into groups based on shared characteristics. (2) Social identification: adopting a group's identity and gaining a sense of belonging. (3) Social comparison: comparing your in-group favourably against out-groups.
Q: What was the aim of Sherif's Robbers Cave experiment?
A: To investigate whether strangers brought together with common goals would form a cohesive group, and whether competition between two such groups would produce hostility.
Q: Describe one finding from each of the three stages of the Robbers Cave experiment.
A: Stage 1, boys bonded within their groups and expressed dislike of the other group before even meeting them. Stage 2, competition led to open hostility including raiding huts and burning flags. Stage 3, superordinate goals (such as fixing a blocked water supply together) successfully reduced hostility, while mere contact did not.
Q: Explain the difference between personal identity and social identity.
A: Personal identity concerns individual traits and preferences (what makes you unique). Social identity concerns the groups you belong to and how those memberships shape your self-concept.
Q: What is a superordinate goal, and why is it important in Sherif's study?
A: A superordinate goal is one that can only be achieved through cooperation between groups. In Sherif's study, superordinate goals were the only method that successfully reduced intergroup hostility; mere contact without a shared goal was not enough.
SIT connects directly to conformity research (see the Abrams et al. study in the companion notes), because in-group identity affects how willing people are to go along with the group. It also links to prejudice and discrimination: the "us vs. them" comparison stage explains why stereotypes and out-group hostility emerge. More broadly, SIT is the theoretical backbone for self-categorisation theory, which Turner developed to explain how people shift between personal and social identities depending on context.
Social identity theory, SIT, Henri Tajfel, John Turner, social categorisation, social identification, social comparison, in-group, out-group, in-group favouritism, in-group bias, us vs. them, intergroup relations, intergroup conflict, superordinate goal, Robbers Cave experiment, Sherif study, Muzafer Sherif, minimal group paradigm, self-categorisation theory, group dynamics, group membership, salience, salient identity, prejudice, discrimination, conformity, PSY 1100, General Psychology, Ohio State