Implicit processing of facial features: Evidence from human electrophysiology

In this study, we used ERPs to investigate neural correlates of face processing. More specifically, we utilized a masked priming paradigm to investigate implicit processing of the eyes and mouth in upright and inverted faces, using prime duration of 50 ms. Three types of prime-target pairs were used: 1. congruent (e.g., open eyes only in both prime and target); 2. incongruent (e.g., open eyes only in prime and open mouth only in target) and 3. dual (both mouth and eyes open in the prime only followed by either type of target, i.e., either eyes or mouth but not both, open). The identity of the faces changed between prime and target. Participants pressed one button to indicate whether the target face’s mouth was open, and an other if the eyes were open. The behavioural results indicated a congruent priming effect for both upright and inverted faces. In addition, we found an enhanced negativity at about 200 ms after target presentation. The amplitude of the N200-like depended on the relation between prime and target, being smaller when the stimuli were congruent in both upright and inverted faces. This N200-like was followed by a P300 component, which was influenced by the three conditions, with incongruency and dual producing a smaller positivity than congruency in both upright and inverted faces. Moreover, when the stimuli were presented upside down, the N200 and the P300 effects took place about 30 ms later. The functional significance of these ERP effects is discussed in relation to unconscious perception and configural face processing.