In this commentary we suggest that Fincher & Thornhill's (F&T's) parasite-stress theory of social behaviors and attitudes can be extended to mating behaviors and preferences. We discuss evidence from prior correlational and experimental studies that support this claim. We also reanalyze data from two of those studies using F&T's new parasite stress measures.

Mating motivation likely plays a role in bias to attractive individuals, but there are other complementary theories drawn from the evolutionary literature related to competition, friendship, and leadership selection that also make relevant predictions concerning biases towards attractive individuals. The relative balance of these factors will be context dependent and so help explain why the pattern of bias is sometimes variable.