Perceivers underestimate within-group variability, inflating perceived group differences.

Evidence

In terms of within-group dispersion, participants generally underestimated the actual variability in both target groups, again suggesting that they overestimated the relative difference between the two groups. And this underestimation was found for both positively and negatively valenced attributes. Interestingly, this underestimation of variability was particularly strong toward the African American target group compared to the white target group. — , Rudman, Laurie A - On the Nature of…, 881