Categorical perception of male and female faces and the single-route hypothesis

Categorical perception (CP) has been demonstrated for face identity and facial expression, while conflicting results have been reported for sex. Furthermore, the question whether processing of sex and identity information is linked remains open. Based on extensive ratings of faces and sex morphs from our face database, we created 'controlled' male and female faces with similar perceived degrees of 'maleness' and 'femaleness'. We then examined CP of sex for these faces with classical discrimination and classification tasks using sex continua. Participants were naive (1), or had been familiarized with average faces of both sexes (2), or with the 'controlled' male and female faces (3). Our results confirm the lack of naturally occurring CP for sex in (1). Furthermore, they provide more evidence for the linked processing of sex and identity, as only participants in (3) showed clear CP. We found no evidence that familiarization with sex information (as given by average male and female faces) transfers to individual faces