Preference for attractive faces is species-specific

Studies on facial attractiveness in human adults, infants, and newborns have consistently reported a visual preference for faces rated as attractive compared to faces rated as unattractive. Biological accounts of facial attractiveness have typically presented such preferences as arising from adaptations for mate choice or as by-products of general sensory bias. In this cross-species study, we examined whether explicit ratings of attractiveness made by human judges would predict implicit visual preferences in other humans and also in rhesus macaques, and if they do, whether such preferences would extend beyond conspecific faces. Results showed that human ratings of attractiveness can predict implicit preferences in non-human primates (macaque monkeys, Macaca mulatta). However, we also found a species-specific effect of face attractiveness in which humans showed a visual preference for human faces (but not macaque faces) rated as attractive, and macaques displayed a visual preference for macaque faces (but not human faces) rated as attractive. Overall, the findings suggest that attentional bias toward attractive faces is neither the result of an exclusive operation of mate choice adaptation mechanisms, nor does it reflect the sole influence of a general sensory bias, but rather reflects their interaction. The influence of a general sensory bias may be modulated by the categorization of a face as conspecific or heterospecific, leading to species-specific preference for attractive faces.