Is it a he or a she? Behavioral and computational approaches to sex categorization.

Can people categorize the sex of neonate faces? Our experiment tested the sex categorization of neonate faces by adult participants. We used a set of 120 Caucasian faces (adults and 4-day-old neonates) that were presented just once to a large sample of participants. A computational model of low-level visual processing, based on Gabor filters, was used to explore the relation between spatial-frequency information and sex categorization. The results showed that participants were able to categorize the sex of the faces, but were less accurate with neonate (d' = 0.36, β = -.97) than with adult (d' = 3.02, β = -.93) faces. Moreover, faces were more frequently categorized as boys' than girls' faces. The computational model suggests that specific spatial-frequency channels carry most of the useful information for the categorization task. Overall, the findings reveal that subtle differences in neonate facial structure were enough to allow the sex categorization of neonate faces, although accuracy was low in both adults and the computational model of low-level visual processing.