Right N170 modulation in a face discrimination task: an account for categorical perception of familiar faces

Behavioral studies have shown that two different morphed faces belonging to the same identity are harder to discrim-inate than two faces stemming from two different identities. The temporal course of this categorical perception effect has been explored through event-related potentials. Three kinds of pairs were presented in a matching task: ~1! two different morphed faces representing the same identity ~within!, ~2! two other faces representing two different identities ~between!, and ~3! two identical morphed faces ~same!. Following the second face onset in the pair, the amplitude of the right occipitotemporal negativity ~N170! was reduced for within and same pairs as compared with between pairs, suggesting an identity priming effect. We also observed a modulation of the P3b wave, as the amplitude of the responses for within pairs was higher than for between and same pairs, suggesting a higher complexity of the task for within pairs. These results indicate that categorical perception of human faces has a perceptual origin in the right occipitotemporal hemisphere