4.2 Article 4
Neurophysiological bases of age and gender perception on human faces

Y. Mouchetant-Rostaing and M.H. Giard

Soumis à Cerebral Cortex

ABSTRACT

According to the Bruce and Young’s model (B&Y, 1986), extraction of physiognomic (age, gender or race) information from faces is achieved through a functional mechanism (the Directed Visual encoding module) distinct from, and activated following, the Structural encoding module. To test this model, we used scalp event-related potentials (ERPs) to compare the neuroelectric activities associated with the structural encoding of facial features with those elicited by age and gender processing. In one session, the faces were of the same gender (female) and of one age range (young or old), preventing any gender or age discrimination. In a second session, faces of young and old women were randomly intermixed but the age was irrelevant for the task, hence age discrimination was assumed to be incidental. In the third and fourth sessions, faces had to be explicitly categorized according to their age or gender, respectively (intentional discrimination). Neither age nor gender processing had effect on the occipito-temporal N170 component assumed to be associated with facial structural encoding. Rather, the three age and gender discrimination conditions induced similar fronto-central activities around 145-185 msec. Altogether these results provide electrophysiological support for the B&Y hypothesis according to which age and gender from faces are processed through a common functional module different from the Structural encoding module. Against the predictions of this model, however, our findings indicate parallel, rather than sequential, activations of these modules. Additional ERP effects were found at early latencies (45-90 msec) in all three discrimination conditions, and around 200-400 msec during explicit age and gender discrimination. These effects, however, previously found in control conditions manipulating non-face stimuli, might be related to more general categorization processes.