We all like to think that we are fair, reasonable people. Most of us feel confident that we (unlike others) are free from bias and prejudice, and that the way we see and treat other people must be warranted. However, over the years, research on in-group bias has shown that group membership affects our perception on a very basic level—even if people have been sorted into groups based on totally meaningless criteria.
One classic study illustrating the power of this bias comes from the psychologists Michael Billig and Henri Tajfel. In a 1973 experiment, participants started out by looking at pairs of paintings and marking down which one they preferred. At this point, some of the participants were told that they’d been assigned to a specific group based on their choices of painting, while others were told they were assigned to a group by a random coin toss. (As a control, other participants weren’t told anything about being in a group, and were merely assigned a code number.)
After this, each participant went into a cubicle, where they were told they could award real money to other participants by marking it down in a booklet. The other participants were listed by code number, so their identities were concealed; however, the code number indicated which of the two groups they had been assigned to.
This study was designed so that the researchers could tease apart the possible causes of in-group bias. Would people be more generous to their group members even when they were told that the groups had been decided randomly? Or would this effect only appear when participants were told that the groups were based on painting preference so that people felt that they had something in common with their group mates?
The results showed that people gave more money to members of their in-group regardless of why that group had been formed in the first place: people were more generous to their in-groups, even when they had been assigned by a coin toss.3 Experiments that follow this same basic outline, known as the minimal group paradigm (MGP), have been repeated time and time again, demonstrating that the favoritism people show for their own group doesn’t need to founded in anything particularly meaningful.
But in-group bias goes beyond kindness to our in-group; it can also spill over into harm towards our out-group. Another famous study illustrating in-group bias is the Robbers Cave study, conducted by Muzafer Sherif. In this experiment, 22 eleven-year-old boys were brought to a mock summer camp and divided into two teams, the Eagles and the Rattlers. The teams were separated, and only interacted when they were competing in various activities. The two teams showed increasing hostility towards each other, which eventually escalated into violence (leading some to call the experiment a “real-life Lord of the Flies”).9,16 Although there were a number of problems plaguing the experiment, including a harsh environment that may have made the boys more anxious and aggressive than they would have been otherwise,10 Sherif’s study is often seen as a demonstration of how group identity can become the foundation for conflict.
Another troubling finding is that in-group bias, and the prejudice that goes along with it, shows up in humans from a very early age. Children as young as three show favoritism for their in-group, and research in slightly older children (ages five to eight) found that, just like adults, kids showed this bias regardless of whether their group had been assigned randomly, or based on something more meaningful.5
Group memberships form part of our identities
There are a few theories of why in-group bias happens, but one of the most prominent is known as social identity theory. This approach is founded on a basic fact about people: we love to categorize things, including ourselves. Our conceptions of our own identities are based partially on the social categories we belong to. These categories could involve pretty much any attribute—for example, gender, nationality, and political affiliation are all categories we place ourselves into. Not all of these categories are equally important, but they all contribute to the idea we have about who we are and what role we play in society.6 Categorization processes also compel us to sort people into one group or another.
Another basic truth about people: we have a need to feel positive about ourselves, and we are frequently overly optimistic about how exceptional we are compared to other people. These processes of self-enhancement guide our categorizations of ourselves and others and lead us to rely on stereotypes that demean the out-group and favor our in-group. In short, because our identities are so heavily reliant on the groups we belong to, a simple way to enhance our image of ourselves is by giving a shiny veneer of goodness to our in-group—and doing the opposite for our out-group.4
Research that supports social identity theory has found that low self-esteem is linked to negative attitudes about people belonging to out-groups. In one Polish study, participants completed several questionnaires, including one on self-esteem, one on collective narcissism, one on in-group satisfaction, and one on hostility towards out-groups. (Collective narcissism and in-group satisfaction both involve holding positive opinions of a group that one belongs to, but in collective narcissism, membership in that group is pivotal for a person’s self-concept; meanwhile, in-group satisfaction doesn’t necessarily mean that belonging to a group is so central to someone’s identity.)
The results showed that self-esteem was positively correlated with in-group satisfaction, and negatively correlated with collective narcissism. Put another way, for people with low self-esteem, group membership was more likely to be a central fixture of their identity. Low self-esteem was also linked with out-group derogation.7 Taken together, these results suggest that people with low self-esteem feel a more urgent need to elevate their own group above others because a larger slice of their identity depends on their belief that their group is better.
We expect reciprocity from others
The social identity theory was put forward by Billig and Tajfel, the researchers who invented the minimal group paradigm, and is the commonly-accepted explanation for in-group bias. However, some researchers have argued that Billig and Tajfel’s research didn’t account for an important social norm: the norm of reciprocity, which requires us to repay kindnesses that others have done for us.
In one study, Yamagishi et al. (1998) replicated one of Billig and Tajfel’s original MGP studies, with one modification: some of the participants were paid a fixed amount by the experimenter, rather than receiving money that had been awarded to them by other participants. This made it clear to these participants that the decisions they made about how to allocate money would have no bearing on the rewards they themselves received at the end of the experiment. As the researchers had predicted, this group did not show any evidence of in-group bias: they divided up their money equally between in-group and out-group members.8
These results contradict the conclusion, drawn by other researchers, that in-group bias arises from merely belonging to a group. Rather than springing up automatically wherever a group is formed, it might be the case that group favoritism only happens when people have the expectation that their good deeds will be repaid by their group members. Put differently, having an in-group to belong to seems to give rise to “group heuristics”—the expectation of reciprocity from in-group members, but not necessarily out-group members.