Outgroup homogeneity bias

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

Interestingly, 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" whom 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.

See also: group-serving bias, list of cognitive biases.

References

• Mullen, B. & Hu, L. (1989). Perceptions of ingroup and outgroup variability; A meta-analytic integration. Basic and Applied Social Psychology, 10, 233-252.
• 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.