Do capuchin monkeys (Sapajus apella) prefer symmetrical face shapes?

In humans, facial symmetry has been linked to an individual's genetic quality, and facial symmetry has a small yet significant effect on ratings of facial attractiveness. The same evolutionary processes underlying these phenomena may also convey a selective advantage to symmetrical individuals of other primate species, yet to date, few studies have examined sensitivity to facial symmetry in nonhuman primates. Here we presented images of symmetrical and asymmetrical human and monkey faces to tufted capuchin monkeys (Sapajus apella) and hypothesized that capuchins would visually prefer symmetrical faces of opposite-sex conspecifics. Instead, we found that male capuchins preferentially attended to symmetrical male conspecific faces, whereas female capuchins did not appear to discriminate between symmetrical and asymmetrical faces. These results suggest that male capuchin monkeys may use facial symmetry to judge male quality in intramale competition.