Behavioural and ERP correlates of eye-movement patterns in face perception

Faces all show the same basic facial features in the same general arrangement, but observers do not all adopt the same eye-movement patterns when looking at them. We conducted two experiments to investigate how face-viewing preferences affect face-specific event-related potentials (ERPs). In Experiment 1, participants were asked to complete a free eye-movement face identification block and two fixation number-controlled blocks in which the initial fixation location was restricted to the left eye or the nose. During this task, we used EEG to record participants’ scalp electrical potentials. Participants were separated into two groups according to their eye movements in the free eye-movement block, with an upper-focused group who favored the eyes of faces, and a lower-focused group who favored the nose and mouth. In fixation number-controlled blocks, the upper-focused group performed better, fixated longer, and elicited a larger N170 amplitude for the eye-fixation condition than the nose-fixation condition. In contrast, the lower-focused group performed and fixated evenly and elicited comparable N170 amplitudes between fixation conditions. In addition, the P1 component was larger for the nose-fixation condition than the eye-fixation condition, and this difference was bigger for the lower-focused group than the upper-focused group. On the other hand, the P1 appeared to have no relation to behavioral performance. In Experiment 2, new subjects completed two fixation duration-controlled blocks in which subjects were asked to keep fixating on the left eye or the nose of faces for 250ms or 500ms, and the behavioral and ERP results in Experiment 1 were replicated. These findings suggest that face identification is associated with an individual’s favored looking pattern tuned by fixation location on a face, and the N170 provides an index of this identification performance.