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According to the outgroup homogeneity bias, individuals see members of their own group as being relatively more varied than members of other groups.

This bias was found to be unrelated to the number of group and non-group members individuals knew. You might think that people thought members of their own groups were more varied and different simply because they knew them better, but this is actually not the case. The outgroup homogeneity bias was found between groups such as "men" and "women" who obviously interact frequently.

The implications of this effect to stereotyping is obvious, and it may be related to confirmation bias.

A similar bias on the individual level is the trait ascription bias. Compare to the group attribution error and the dilution effect.

In fiction

An example of this is that in science fiction universes, such as Star Trek, humans are almost always the only race with multiple cultures; alien races are universally depicted as monocultures.

See also

• group-serving bias
• list of cognitive biases
• outgroup

References

• Quattrone, G. A., & Jones, E. E. (1980). The perception of variability within in-groups and out-groups: Implications for the law of small numbers. Journal of Personality and Social Psychology, 38, 141-152.
• Quattrone, G. A. (1986). On the perception of a group’s variability. In S. Worchel & W. G. Austin (eds.) Psychology of intergroup relations, 2nd ed. Chicago: Nelson-Hall.
• Mullen, B. & Hu, L. (1989). Perceptions of ingroup and outgroup variability; A meta-analytic integration. Basic and Applied Social Psychology, 10, 233-252.