Ingroup-Outgroup Bias

Evidence of conflict and discrimination between groups is all around, which is not to say that this is inevitable, as many groups coexist peacefully most of the time. Ingroup bias refers to a form of favoritism toward one’s own group or derogation of another group. Many theories of intergroup relations in social psychology try to explain this phenomenon. Ingroups are groups to which a person belongs, and outgroups are groups to which a person does not belong (and which could therefore become target for ingroup bias). There is an almost infinite number of groups to which a person belongs, depending on how he or she categorizes the social world.

Ingroup-Outgroup BiasGender, ethnicity, occupation, economic and social position are all meaningful dimensions by which a person can define him- or herself and others in terms of ingroups and outgroups; this is a process of social (and self) categorization. Ingroup bias can take many forms and on many dimensions, both evaluative and behavioral. Evaluative ingroup bias refers to the rating of one’s own group as better (more positive, less negative) on dimensions of judgment, and as such, it is closely related to the concept of prejudice. In behavioral terms, ingroup bias refers to the tendency to favor the ingroup over the outgroup in some way, for example, in terms of the allocation of resources or rewards: a form of discrimination. Outgroup bias—the tendency to favor the outgroup over the ingroup—is much less common than ingroup bias but by no means absent in intergroup relations.

One of the key objectives of research in intergroup relations has been to understand and explain evidence of ingroup bias in it various forms, as a necessary step to reduce and resolve intergroup discrimination. One obvious and recurring explanatory factor is self-interest: People may favor their own groups, and derogate outgroups, because it benefits them through resources or rewards. This is the basic idea behind the realistic group conflict theory, which explains such bias in terms of real conflicts of interests between groups that are competing with each other for scarce resources (e.g., land, jobs, status). This provides a straightforward and compelling explanation for many of the intergroup conflicts seen around the world, especially where resources are at stake.

However, research has also shown that conflicts of interests and self-interest motives may not even be necessary for ingroup bias to occur. The so-called minimal group studies show that people tend to favor their own group in terms of reward allocations even when they are categorized on a trivial basis (e.g., preference for painters, by a coin toss), such that they do not even know who is in the ingroup or the outgroup, and even when they do not meet them. This is true even when they do not allocate rewards to the group as a whole (where they could benefit personally) but only individual members of the ingroup. One feature of these experiments was the development of reward matrices designed to measure different reward strategies. It was possible to distinguish between strategies that simply favored the ingroup (maximizing ingroup profit) from a form of discrimination that maximizes the difference in rewards given to ingroup and out-group (i.e., even potentially at the cost of the absolute reward to the ingroup), which could be seen as genuinely more discriminatory. These experiments found evidence of this maximizing difference strategy. These findings led to the development of social identity theory, which aimed to explain why people might discriminate in favor of their group for more symbolic psychological reasons than because of mere self-interest. The explanation proposed for this was that such discrimination provides the group with a positive distinctiveness that can enhance the social identity and self-esteem of ingroup members.

However, the explanations for discrimination in minimal groups remain hotly contested. Some have argued that ingroup bias can be explained by self-interest after all, if it is assumed that there is an expectation of reciprocity of mutual reward among ingroup members. This still leaves open the question of why the ingroup should feel this ingroup reciprocity. Evolutionary arguments have been advanced, proposing that people may have good reasons to trust and reward those within their ingroup, who may in turn help them in the future. This may explain ingroup favoritism but may less easily explain evidence of maximum differentiation or outgroup derogation. More recently social identity theory has been extended by emotion theory to explain the more malicious forms of prejudice and discrimination toward outgroups and the different forms this may take, depending on the specific relations between the groups (e.g., depending on power, status relations). Clearly ingroup bias is not just a matter of rational self-interests but may also include more symbolic and emotional benefits to the group.

One weakness of the realistic conflict approach is that it seems to imply that ingroup bias should occur when there are conflicts of interest, and this is clearly not always the case. Although intergroup conflict is newsworthy, intergroup stability is more common despite pervasive differences in wealth status and other resources. Sometimes groups seem to accept their disadvantaged status and even show examples of out-group bias. A good example of this is the classic doll studies in which African American children presented with a Black or White doll to play with chose the White doll (at least in the early demonstrations), an apparent outgroup preference. Social identity theory is able to explain this because it only predicts conflict and social competition when the group relations are unstable and perceived as illegitimate (and thus insecure). After the civil rights movement, the doll studies no longer showed outgroup bias, indicating that African Americans no longer accepted their lower status as legitimate.


  1. Hewstone, M., Rubin, M., & Willis, H. (2002). Intergroup bias. Annual Review of Psychology, 53, 575-604.
  2. Tajfel, H., & Turner J. C. (1986). The social identity theory of intergroup behavior. In S. Worchel & W. G. Austin (Eds.), Psychology of intergroup relations (pp. 7-24). Chicago: Nelson Hall.