While in-group bias can help us feel connected to members of our group, it can also harm our relationships with people who don’t happen to belong to the same group as we do. Our tendency to favor in-group members can cause us to treat outsiders unfairly, and perceive identical behaviors differently depending on whether they were performed by in-group or out-group members. We might even feel justified in committing immoral or dishonest actions, so long as they benefit our group.¹ Let’s take a closer look at these effects.

Reduced empathy for out-group members

One way in-group bias can affect us as individuals is by reducing our sense of empathy toward out-groups. Empathy—our impressive human ability to understand and share the emotional states of others—plays a key role in prosocial behavior.¹⁷ Research shows that viewing others in pain activates brain regions that are also active when we experience pain firsthand. Being able to experience the distress of others as if we’re experiencing it ourselves can motivate acts of altruism, in which we help others without the expectation of reward or reciprocity.

However, research also shows that in-group favoritism can compromise our ability to empathize with out-group members. In brain scan studies, for example, participants tend to have much stronger empathy-related neural responses when watching in-group members in pain than out-group members.¹⁷ This difference in empathy can make us less willing to help out-group members, and may even mean we have a greater tolerance for their pain.

Resistance to external ideas

Favoring one’s own group can also make us resistant to ideas that come from out-groups. In fact, research shows that we are less likely to learn from individuals belonging to a different group than from those within our own group. In one study, politically left-wing participants performed worse at an observational learning task when they believed the model was from a right-wing out-group than a left-wing in-group.¹⁸ More specifically, researchers found that participants learned similarly when observing both in-group and out-group outcomes, but learned less well when only observing out-group actions. This suggests that participants gave less weight to the actions of out-group members, essentially downplaying the relevance of out-group members’ behavior when deciding which actions to take themselves.

In the same way, a negative out-group bias can cause us to overlook valuable information that might come from members of other groups. We might be less likely to adopt useful strategies or insights from others or we might pass over information that could help us make better decisions. Whether this means we brush off valuable career advice from someone from a different social circle or ignore practical home improvement tips from a neighbor of the opposite gender, in-group bias can cause us to miss out on knowledge just because it came from someone outside our group.

In-group bias is a major component of prejudice and discrimination, causing people to extend extra privileges to people in their own in-group while denying the same courtesy to outsiders. This prejudice creates unequal outcomes for marginalized groups. In the legal system, for example, judges and juries might favor defendants who are the same race, gender, or religion as they are, and rule unfairly against those who are not.² Here’s a closer look at some of the ways in-group bias can lead to large-scale effects.

Resource distribution inequalities

Social dilemmas and economic games, like the well-known prisoner’s dilemma, show that people often cooperate even when it would be personally beneficial to act selfishly. However, some variations on trust games show that people are less likely to cooperate with out-group members than in-group members.¹⁹ For example, in public goods dilemmas in which resources are limited, participants are more likely to accept resource allocation proposals that benefit their in-group than those that benefit out-groups or result in fair distribution.²⁰ 

On a larger scale, this can create inequalities in resource distribution that benefit in-groups of decision-makers while disadvantaging out-groups, even if members of out-groups may be more deserving. In decision-making environments where out-group voices are underrepresented, such as in government or on school boards, this can lead to policies that unfairly benefit the dominant group.

Intergroup relations and social division

It’s not hard to imagine how in-group bias can lead to social division. Favoring one’s own group over others can make it difficult for different countries and cultures to cooperate, fueling xenophobia and contributing to conflict on a global scale. Even on a slightly smaller scale, the tendency to separate ourselves into groups based on similar characteristics—whether related to culture, religion, socioeconomic status, or otherwise—can break down the social cohesion that holds societies together.²¹ Groups can start to prioritize their own interests over broader societal goals, weakening intergroup relations, creating conflict within societies, and overshadowing the common good. Even among workplace teams, in-group bias can cause hiring and promotional decisions that favor those who fit in with the dominant group, stifling diversity and its crucial contributions to innovation.

From a political perspective, in-group bias can lead to polarized partisanship where decisions are less about objectively assessing policies and more about aligning with other members of one’s in-group.²¹ This results in an “us” vs. “them” mindset that decreases willingness to cooperate and find common ground, even when everyone is working toward mutual goals. Even worse, out-group derogation can amplify hostility by causing in-groups to overestimate the threat of the “other,” allowing them to justify the unfair treatment of out-group members.

We all like to think that we are fair, reasonable people. Most of us feel confident that we (unlike others) are free from prejudice and treat other people equally. However, over the years, research on in-group bias has shown that group membership subconsciously affects all of our perceptions at a very basic level—even if people are sorted into groups based on totally meaningless criteria.

One classic study illustrating the power of this bias comes from psychologists Michael Billig and Henri Tajfel. In a 1973 experiment, participants began by looking at pairs of paintings and determining which one they preferred. At this point, some participants were told that they’d been assigned to a specific group based on their painting preferences, while others were told they had been 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 awarded real money to other participants by marking it down in a booklet. The other participants were listed by code number to conceal their identity; however, the code number indicated which of the two groups each participant was assigned to.

The researchers intentionally designed this study so that they could tease apart the possible causes of in-group bias. Would people be more generous to their group members even when the groups were random? Or would this effect only appear when the groups were based on painting preference because participants felt they had something in common with their teammates?

The results showed that people gave more money to members of their in-group regardless of how that group was formed in the first place. In other words, people were more generous to their in-groups, even when a coin toss had assigned them.³ Experiments that follow this same basic outline, known as the Minimal Group Paradigm (MGP), have been repeated time and time again with the same results. No matter what, favoritism never seems to depend on any meaningful connection besides being in the same group.

But in-group bias goes beyond kindness to our in-group; it can also spill over into harm toward out-groups. Another famous study illustrating in-group bias is the Robbers Cave study, conducted by Muzafer Sherif. In this experiment, 22 eleven-year-old boys attended a mock summer camp and were divided into two teams: the Eagles and the Rattlers. The teams were kept separate and only interacted when competing in various activities. 

The two teams showed increasing hostility toward each other, which eventually escalated into all-out violence (what some called a “real-life Lord of the Flies”).^9,16 Although there were a number of ethical issues with 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 still seen as a frightening demonstration of how group identity alone can become the foundation for conflict.

Another troubling finding is that the prejudice sparked by in-group bias emerges in humans from a very early age. Children as young as three show favoritism toward their in-group, and research in slightly older children (ages five to eight) has found that they showed this bias regardless of whether their group had been assigned randomly or meaningfully—just like adults.⁵

Group memberships form part of our identities

There are a few theories about why in-group bias happens, but the most prominent is known as Social Identity Theory, proposed by Tajfel and his colleagues. This approach is founded on a basic fact about people: we love to categorize things, including ourselves. Self-Categorization Theory, an extension of Social Identity Theory, suggests that the way we conceptualize our identities depends on the social categories we belong to. These categories could involve nearly 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 our sense of who we are and our role 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 we rank compared to others. Our desire for self-enhancement guides our categorizations and leads us to rely on stereotypes that favor our in-group and demean the out-group. In short, since our identities heavily rely 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 

Researchers often refer to this as the “in-group love theory.”¹⁹ Rather than favoring in-groups due to a dislike of out-groups, in-group love is thought to stem from a desire to support or protect one’s group because it is seen as an extension of the self. Building on this, the positive feelings and approval we receive from others when we support our group serve as a powerful social reward that reinforces behaviors that strengthen in-group favoritism.

The role of self-protection

Collective self-esteem, which describes how positively one tends to view one’s group memberships, also contributes to in-group bias. Those with high collective self-esteem are considered more confident in their social identity, and they tend to evaluate their social group more positively. However, those with low collective self-esteem (who feel less confident about their group membership) are more likely to protect their social identity through out-group degradation.⁷

In fact, research supporting Social Identity Theory has found that low self-esteem is linked to negative attitudes toward 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 toward out-groups. Collective narcissism and in-group satisfaction both involve holding positive opinions about the group to which one belongs, while collective narcissism is dependent on external validation. Meanwhile, in-group satisfaction means that belonging to a group is not as 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

Billig and Tajfel’s Social Identity Theory 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: reciprocity, which prompts us to repay others’ kindness.

In one experiment, 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 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 previous conclusions that in-group bias arises from merely belonging to a group. Rather than springing up automatically wherever a group is formed, group favoritism may occur only when people have the expectation that their good deeds will be repaid by their group members. In other words, having an in-group to belong to gives rise to “group heuristics”—the expectation of reciprocity from in-group members, but not necessarily out-group members.

Like all cognitive biases, in-group bias happens without us realizing it. Although we may believe that we are being fair and reasonable in our judgments of other people, in-group bias demonstrates that we may not be as charitable to outsiders as we are to people more “like us.” When it comes to judgments we make about other ethnic groups, in-group bias fuels ethnocentrism: the tendency to use our own culture as a frame for evaluating other people. This narrow lens usually results in seeing other cultures as inferior rather than simply different.

In-group bias has serious, real-world consequences, particularly for people belonging to marginalized groups (whether based on ethnicity, gender, religion, or other factors). In the legal system, for example, an in-group bias toward one’s own ethnic group can influence a judge’s decision on whether or not to detain a suspect.²

In-group bias can also lead us to be more lenient than we necessarily should be toward in-group members who have done something wrong. In one study, researchers found that people who scored high on measures of modern racism were quick to excuse bad behavior committed by a European American person and to praise them for their virtues. When it came to similar behavior perpetrated by an African American person, however, they were not so kind.¹¹ As this study demonstrates, in-group bias can prevent us from holding in-group members accountable for their own behavior.

This bias also has unfortunate moral implications for our own decision-making. Research has found that people are more willing to lie or cheat in order to benefit their in-group, sometimes even when they themselves do not stand to gain anything from this dishonesty.¹ Our favoritism for our own group is apparently so strong that many of us will bend our morals for the sake of the tribe. This can obviously lead to poor choices, especially for people who lack self-esteem and are particularly desperate to gain the approval of their peers.

In-group bias is very difficult to completely overcome because it sneakily operates below the surface of our consciousness. That being said, behavioral research points to some tactics that might help reduce in-group bias.

Capitalize on people’s self-interest

While it sounds counterintuitive, some researchers have tried to exploit people’s self-interest in order to reduce their in-group bias. One study compared two games, known as the Dictator Game (DG) and the Ultimatum Game (UG). In both games, players decide how to split a sum of money between themselves and a recipient. In the DG, once the deciding player has made a decision, the recipient has no choice but to go along with it. However, in the UG, the recipient can choose to either accept or reject the first player’s offer. If they reject it, neither player receives anything.

In this study, participants played either the DG or the UG and were told that their partner (who didn’t actually exist) either shared their view on abortion or held the opposite view. When participants were playing the DG, they showed significant in-group bias, offering more money to in-group members than to out-group members. However, in the UG, this bias disappeared entirely.¹² These results reveal that concrete incentives to treat people equally might be an effective strategy for reducing in-group bias.

Try a little teamwork

Remember the Robbers Cave study, where boys were separated into teams and pitted against each other? After making archenemies out of the Eagles and the Rattlers, Sherif and his colleagues were able to reduce the hostility between the two teams by forcing them to cooperate with each other. To achieve this, the researchers artificially cut off the camp’s drinking water supply and told the boys that they would all have to work together to fix it. (It was the 1950s, so you were allowed to put children in a forest and deprive them of water for the sake of science.) Through this exercise, along with a few others that gave the two teams a shared goal, they eventually got on friendly terms.

More recent evidence supports the idea that encouraging cooperation between groups can reduce in-group bias. By interacting with an out-group, our categorizations of others can expand to include out-group members in a new, superordinate group identity. And even though Sherif theorized that it was key for both groups to share a common fate, recent research suggests that this isn’t the case: interacting with one another is enough.¹³ Wherever possible, encouraging cooperation between groups is a useful strategy.

What is the black sheep effect?

The Black Sheep Effect is a phenomenon in social psychology in which people tend to judge unlikable or unfavorable members of their in-group more harshly than those of an out-group.²² This is thought to occur because groups are driven to maintain a cohesive group identity and reputation, so any members who threaten this cohesion—perhaps because they think differently or behave in a way that deviates from group norms—are seen as threats to the group identity. As a result, in-group members often distance themselves from the “black sheep” by withdrawing their support or excluding them from social recognition.

The Black Sheep Effect contrasts with typical in-group bias, as it means in-group members are not always automatically favored, especially in the face of reputational concerns. Instead, it shows that people can demonstrate social preferences by supporting socially desirable in-group members while at the same time showing more aversive reactions to socially undesirable in-group members. 

An early study on the Black Sheep Effect demonstrates what this might look like in a real-world setting.²² In the study, Belgian students watched a news broadcast about a football fan riot. The participants were asked to imagine that the riot was either started by Belgians (in-group) or Germans (out-group), and then rate these imaginary rioters on various value-based traits. In line with the Black Sheep Effect, the Belgian participants judged the Belgian rioters more harshly than the Germans.

Is there a neurocognitive component to in-group bias?

Brain imaging studies have revealed that various neurocognitive processes are involved in our bias toward in-group members. For example, functional Magnetic Resonance Imaging (fMRI) studies show that the medial prefrontal cortex, a brain region involved in higher-order cognitive functions, shows increased activity when people engage in group categorization tasks.²³ More specifically, people tend to show more activity in this brain region when they divide money between in-group and out-group members than when dividing money between two in-group or two out-group members. 

There is also more brain activity in this region when people show in-group favoritism—for example, when they give more money to in-group members than to out-group members, compared with fair trials where they distribute money equally. Interestingly, this part of the brain is also activated when we think about our own personal qualities. As a result, researchers believe that the activation of the medial prefrontal cortex during social categorization supports the social identity approach to in-group bias, in which group members are thinking about their in-group as an extension of the self.²³ This suggests that in-group favoritism may occur because one’s group is neurologically associated with one’s own identity.

How does in-group bias interact with other cognitive biases?

In-group bias can interact with several other cognitive biases to shape our judgments and behavior. For example, confirmation bias causes us to give more weight to information that supports our existing beliefs. So, if we’re already strongly biased toward our in-group, we may pay more attention to information that confirms our positive view of the group while ignoring or downplaying information that suggests otherwise. For example, football fans from two different universities can watch the same football match but disagree on which team made the most infractions.²³ 

Here’s a quick breakdown of how some other cognitive biases can interact with in-group bias:

• Self-serving bias: Our tendency to attribute positive outcomes to personal qualities and negative outcomes to external factors can work the same way on a group level, so we take credit for group successes while attributing failures to factors outside of the group’s control. 
• Optimism bias: Our tendency to overestimate the likelihood of positive outcomes may also extend to our in-group, causing us to hold more optimistic expectations about the future of our group than about an out-group.
• Observer bias:  When observing others, our expectations can cloud what we’re actually seeing. If we expect an in-group member to perform better than an out-group member in a certain area, we might interpret their behavior more favorably than we would if it were exhibited by an out-group member.
• Irrational primacy bias: This cognitive bias describes how we often rely on the first piece of information we receive about something to influence our perception. As a result, when shared group membership is the first thing we notice about someone—for example, if they are the same race or gender as we are—we might hold a more favorable impression of this person, even when facing new, contradictory evidence.

Along with the above examples, there are many other cognitive biases that impact our social cognition and lead to inaccurate perceptions of ourselves and others. Together, these biases can reinforce our favorable feelings toward in-groups and make it difficult to evaluate out-groups fairly.

What is the difference between in-group bias and ethnocentrism?

In-group bias and ethnocentrism are closely related concepts, but they are not exactly the same thing. Ethnocentrism involves evaluating other cultures based on preconceptions rooted in one’s own culture, often resulting in members of one group feeling that their own culture is superior to others. While in-group bias also describes a tendency to favor members of one’s own group, this is not limited to ethnic groups. It can occur among sports fans, political parties, workplace teams, and even arbitrary groups like blood donors, mothers, or marathon runners.

Of course, favoring one’s group and actively disliking the out-group is closely tied to ethnocentrism. However, research has found that ethnocentrism is not just about disliking out-groups (out-group negativity) or liking in-groups (in-group positivity), but is a much more complex construct that involves various attitudes and beliefs.²⁴ It is driven by both loyalty to one’s own group and prejudice against out-groups. Playing a significant role in modern-day nationalism and being implicated in racial discrimination around the world, ethnocentrism is heavily studied by social psychologists due to its negative effects on intergroup relations.

In-group bias has probably been shaping human history for as long as we’ve been around, but it wasn’t until 1906 that it became an object of academic curiosity. The concept was introduced by the American sociologist William Graham Sumner, known for his work on folkways (social norms specific to a given society or culture). Sumner believed that ethnocentrism (and in-group bias underlying it) was universal among humans.⁴

In the second half of the twentieth century, social psychology started to gain steam as the world struggled to make sense of World War II and the Holocaust. The topic of intergroup relations, and why people could be so irrationally biased against people who weren’t like them, was a major area of interest (as it still is today). 

In the 1960s, Sherif, of Robbers Cave fame, worked with his wife Carolyn to develop Realistic Conflict Theory: an approach that posits group conflict arises from competition over resources. Later, in the 1970s, Billig and Tajfel developed the Minimal Group Paradigm, and Tajfel coined Social Identity Theory (along with another psychologist, John Turner).

Unsurprisingly, we prefer to purchase products that in-group members use—and even look down on products that out-group members advocate. For instance, if all of our friends are flaunting the newest smartphone, we might be inclined to upgrade to help us feel like we’re fitting in and further distinguish ourselves from those with the outdated version. 

Advertising agencies leverage this in-group bias to their advantage, deliberately choosing actors and mottos they know will resonate with a specific clientele. For instance, an ad for a small car dealership may choose actors resembling locals and emphasize their small-town values, while an eco-friendly cosmetic brand may choose an environmental activist to model their products, rather than a celebrity notorious for traveling on private jets.

In fact, brand loyalty often establishes an “us versus them” mentality all on its own. We tend to strongly identify with our material possessions, viewing them as an extension of ourselves. For this reason, we often feel like we belong in a group with others who own the same products as we do, even if the connection is almost meaningless. We’ve all had the experience of being on public transportation and complimenting someone’s shoes because we own the same brand. We feel an affinity toward them simply because we choose the same products as we do, therefore making them like us.

Just as with any other technological innovation, the way that in-group members regard artificial intelligence (AI) determines how willing we are to adopt AI into our lives. For instance, if you work at a start-up with young, tech-savvy employees actively incorporating machine learning into project pipelines, you’ll probably be eager to try using ChatGPT for researching new assignments. Meanwhile, if you work at a well-established company with corporate leaders loyal to traditional procedures, you might be skeptical about how AI is dominating the workplace and less likely to give it a try.

Machine learning can also amplify in-group biases. Datasets that train AI software are usually skewed toward one group or against another—after all, they are made by humans. This means that the algorithm may adapt these prejudices itself, while maintaining the facade of objectivity through its machine exterior. With this in mind, it is essential to stay skeptical of the results AI generates for you; they might be more in favor of one side than you think.

In the lead-up to the 2008 U.S. presidential election, there were two front-runners for the Democratic nomination: Barack Obama and Hillary Clinton. As it turns out, Democrats’ allegiances to a given candidate were sometimes enough to inspire in-group bias.

Researchers recruited Democrats to play the Dictator Game, where they decided how much of a pool of money they would share with an anonymous partner. The participants indicated whether they preferred Obama or Clinton and learned whether their partner agreed or disagreed. The researchers repeated this experiment three times: first, in June 2008, right after Clinton’s concession speech; next, in early August, before the start of the Democratic National Convention (DNC); and finally, in late August, after the DNC had ended.

The results revealed that, in the first two experiments, men showed significant in-group bias, giving significantly more money to partners who shared their choice of candidate. Surprisingly, this bias was not found among women. However, this difference disappeared in the third experiment after the DNC. But why?

The authors of the paper wrote that the 2008 primary season had been a particularly bitter one, and there had been worries in the Democratic Party that spurned Clinton supporters would break from the party and vote Republican. So the goal at the DNC was to foster a broader group identity among Democrats by leveraging support for Obama. The fact that the authors found reduced in-group bias after the DNC makes sense, given that national polls also found a large increase in Obama support among Hillary supporters after the convention.¹⁴

It’s no secret that sports fans take their allegiances seriously, so it’s not surprising that people show in-group bias toward fellow supporters of their own team. In one study, researchers had participants fill out a number of surveys as they were leaving a basketball game. These surveys gauged how invested the participants were in their team and had them rate the behavior of fans of both teams during the game. The results showed that the spectators were biased in favor of their in-group, especially when their team lost. For those who identified strongly with their team, this effect was strongest when the game they had just watched was a home game, as their environment encouraged an even stronger in-group bias.¹⁵

What it is

In-group bias is the tendency to give preferential treatment to members of our own group while neglecting or actively harming members of out-groups.

Why it happens

The main explanation for in-group bias is Social Identity Theory, which posits that membership in various groups comprises a large part of our identities. We need to feel positive about ourselves, and by favorably comparing our groups to others, we enhance our own self-concept. 

Other theories include Realistic Conflict Theory, which says that groups get into conflict when they compete for resources, as well as Group Heuristics Theory, which posits that we are nicer to in-group members only because we expect reciprocity from them.

Example 1 – Democrats and in-group bias in the 2008 election

In the lead-up to the 2008 U.S. presidential election, male Democratic voters expressed significant in-group bias, favoring people who shared their choice of candidate and penalizing others. This bias vanished after the DNC, which prioritized fostering a shared Democratic identity.

Example 2 – Sports fan and in-group bias

Spectators at a basketball game who were heavily invested in their team showed in-group bias when rating the behavior of fans of both teams. This effect was strongest when their team lost or after a home game.

How to avoid it

In-group bias is notoriously difficult to completely avoid, but research shows that we can reduce it by interacting with other groups, as well as by giving people incentives to act in an unbiased manner.

The Similar-To-Me Effect

Unfortunately, in-group bias is only one of many biases pushing us toward those like ourselves and away from those who are different. Others include egocentric bias, ethnocentrism, stereotypes, and several more. Read this article to learn more about how all these factors interact with each other, as well as the groundbreaking research that led to their discovery.

One Unconscious Bias Is Keeping Women Out Of Senior Roles

Historically, men have occupied a greater number of managerial and director positions. According to in-group bias, people tend to hire those who are similar to them, which leads to male executives promoting other men to senior roles. As our writers Melissa Wheeler and Victor Sojo analyze, this phenomenon makes it incredibly difficult for women to gain access to executive and CEO positions. Wheeler and Sojo provide various strategies for combating this bias, as well as methods for ensuring equal treatment in the promotion process.