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Outgroup homogeneity bias

“I tend to underestimate the differences among members of a group when I am not part of it.”


The outgroup homogeneity bias describes our tendency to believe that members of a group we are not part of (the outgroup) are very similar to each other, are principally characterised by stereotypical traits, and have a simple and impoverished emotional life [1], while we believe that members of a group we are part of (the ingroup) are more diversified. Our perception of the outgroup is simplified to allow us to consider the group as a whole, and to ignore qualities that distinguish individual members, which takes less cognitive effort.

Though research in this area has concentrated on this bias in the context of racialised groups, the bias appears in all ingroup-outgroup relationships but is not always expressed with the same intensity. The phenomenon is strengthened when interpersonal relations with members of the outgroup are infrequent [2].


Often our job or profession links us to a particular ingroup, and relegates those who do a different kind of work into an outgroup. As a result, we have a tendency to think that all members of a profession that is different from our own are similar to one another, reducing their traits to the stereotype associated to their job. For example, if we are not an accountant, we may judge someone who is a member of the group “accountants” to be boring, without taking their individual characteristics into account or trying to get to know them as a person.


Our cognitive resources (our ability to observe the environment, process information, reason, concentrate, etc.) are limited. As a result, we must allocate them in a way that allows us to function as well as possible in our environment. It is much more costly, cognitively speaking, to consider a group as composed of many different unique people, which requires the processing of much more information, than it is to consider them as all the same. The most important interpersonal interactions in our lives (the choice of a sexual partner, the exchange of goods and services, power relationships) occur largely within our ingroups, so it is only reasonable to allocate most of our cognitive resources to these kinds of interactions. In contrast, interactions with members of our outgroups are relatively rarer and tend to happen in contexts where the group they belong to seems more important to us than the individual with whom we are dealing (for instance, when we use the services of an accountant to do our taxes, or when a Montreal Canadians fan meets a Boston Bruins fan). From the point of view of the allocation of cognitive resources, the cognitive “cost” of considering the outgroup as composed of complex and varied individuals is higher than any benefit that would be obtained from doing so [3].


This bias is linked to many instances of the perception and persistence of stereotypes. Here are three examples. First, independently of racial prejudice, when the bias occurs among different racial groups, it can lead to a greater acceptance of the privilege or of the racial inequality experienced by our outgroup. It can also lead to a lack of interest in interacting with or befriending members of other racial groups [4]. These consequences can be attributed to the fact that the outgroup homogeneity bias leads us to believe that the privileges or the injustices experienced by our outgroup are a result of the group’s biological characteristics, and therefore deserved. Second, the bias may decrease the empathy we feel for members of our outgroup. This reduction in empathy has been measured in studies that have found that our physiological reaction is weaker when we see a hand that belongs to a different racial group than our own being pricked by a needle than when we see the same thing happen to a hand that belongs to our own racial group [1]. Finally, this bias can make it more difficult for us to recognise the faces of members of our outgroup. This has negative practical consequences on police work, because it makes identification of criminals by eyewitnesses less reliable if the criminal’s face belongs to the witness’ outgroup [3].

Thoughts on how to act in light of this bias

  • Show the person content that demonstrates that the stereotypical traits attributed to the outgroup are not anchored in biology [4].

  • Force ourselves to adopt and actively maintain a positive attitude toward members of our outgroups. This forces us to realise that we share certain aspects of our identity with them, and that we are all part of a bigger group that is simply sub-divided into smaller ones [5].

How is this bias measured?

Several methods are used to measure the outgroup homogeneity bias in an experimental setting. One of these methods is to ask participants to evaluate to what point members of different groups possess a particular character trait. For example, participants must place 100 fictional women and 100 fictional men on a scale representing the possession of a trait such as self-affirmation, by placing them at a greater or lesser distance from a central point representing the trait. Afterwards the results are interpreted using a statistical tool that measures statistical dispersion. The greater the dispersion of members of the outgroup around the particular trait (that is, whether the subjects have placed the members of the fictitious outgroup around the trait at variable distances), the less the bias is judged to be present. On the other hand, if the dispersion is concentrated at one place on the scale (in other words, if almost all of the outgroup members are placed at the same distance from the trait on the scale), the homogeneity bias is judged to be present [2].

This bias is discussed in the scientific literature:


This bias has social or individual repercussions:


This bias is empirically demonstrated:



[1] Sapolsky, Robert M. (2017). Behave: The Biology of Humans at Our Best and Worst. Penguin Press.

[2] Park, Bernadette & Charles M. Judd (1990). Measures and models of perceived group variability. Journal of Personality and Social Psychology 59(2): 173–191.

[3] Ackerman, Joshua M., Jenessa R. Shapiro, Steven L. Neuberg, Douglas T. Kenrick, D. Vaughn Becker, Vladas Griskevicius, Jon K. Maner & Mark Schaller (2006). They all look the same to me (Unless they’re angry): From out-group homogeneity to out-group heterogeneity. Psychological Science 17(10): 836–40.

[4] Williams, Melissa J. & Jennifer L. Eberhardt (2008). Biological conceptions of race and the motivation to cross racial boundaries. Journal of Personality and Social Psychology 94(6): 1033–1047.

[5] Johnson, Kareem J. & Barbara L. Fredrickson (2005). We all look the same to me’: Positive emotions eliminate the own-race bias in face recognition. Psychological Science16(11): 875–81.


Interpersonal level, Representativeness heuristic, Availability heuristic, Need for self-esteem, Need for security, Need for social belonging, Need for cognitive closure

Related biases


Andréanne Veillette is a PhD candidate in Ethics and Public Affairs at Carleton University. She is a member of the Canada Research Chair in Practical Epistemology and the Canada Research Chair in Epistemic Injustice and Agency. 

Translated from French to English by Susan D. Renaud.

How to cite this entry

Veillette, A. (2021). Outgroup homogeneity bias, trans. S. D. Renaud. In E. Gagnon-St-Pierre, C. Gratton, & E. Muszynski (Eds). Shortcuts: A handy guide to cognitive biases Vol. 3. Online:

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