Why Do ‘They’ Often Seem More Alike Than ‘We’ Do?

People can often list fine distinctions within a group they belong to, yet describe another group with the phrase, “They’re all much the same.” Psychology calls this tendency to underestimate relative variation within an outgroup the outgroup homogeneity effect. It does not mean the other group is objectively more uniform, nor does it require open hostility from the observer.

In a classic study, students from two rival universities watched a student said to belong either to their own university or to the rival make a choice, then estimated how many other students at that university would choose the same way. Participants generalised one person’s decision more strongly to the rival university. One possible reason is that when we think about “us”, we have many individual cues, roles and exceptions available. When we think about “them”, the group label is more likely to become the leading cue, pushing individual differences into the background.

Still, “we simply know them less well” is not a complete explanation. A 2007 meta-analysis covering 173 independent samples and 12,078 participants found a small but reliable overall tendency to see more variation in ingroups than outgroups. The pattern changed with the measure used, whether groups were natural or experimentally created, and their relative status; some settings even produced ingroup homogeneity. Group perception depends on experience, but also on the immediate comparison, which identity is salient and how the judgement is elicited.

When an impression takes the form “that group is always like this”, the useful question is not whether to give yourself a moral label. It is whether your evidence consists of many individuals or a few people treated as a sample of the whole group. Group labels compress complexity, but they cannot replace observing variation within the group.

https://doi.org/10.1037/0022-3514.38.1.141
https://doi.org/10.1177/1368430207075153