They all look the same to me (unless they're angry): from out-group homogeneity to out-group heterogeneity.

People often find it more difficult to distinguish ethnic out-group members compared with ethnic in-group members. A functional approach to social cognition suggests that this bias may be eliminated when out-group members display threatening facial expressions. In the present study, 192 White participants viewed Black and White faces displaying either neutral or angry expressions and later attempted to identify previously seen faces. Recognition accuracy for neutral faces showed the out-group homogeneity bias, but this bias was entirely eliminated for angry Black faces. Indeed, when participants' cognitive processing capacity was constrained, recognition accuracy was greater for angry Black faces than for angry White faces, demonstrating an out-group heterogeneity bias.