Being the solo member makes one salient and stereotype-exaggerated

Evidence

In initial perception, categories highlight people who do not fit with the majority. Attention rivets on the solo or token member of a group otherwise homogenous on race or gender. The salience of the solo reveals the social importance of the category that makes the individual stand out. In a group with a solo, the group members are especially categorized along that dimension. Solos attract attention and realize it, which sometimes interferes with their concentration (Saenz, 1994). Solos are perceived in exaggerated, stereotypic ways (Taylor, 1981). — John F. Dovidio, Peter Glick, Laurie A. Rudman, On the Nature of Prejudice, 300