In contrast to some of our previous studieswhich employed real face
photographs, in this studywe used artificially created facial stimuli. Various
face identitieswere obtained using different internal facial features
but all faces had the same bald outline to keep head size constant and to
avoid the hair area to create a zone of darker contrast and to influence
the N170 response. In addition every feature was situated at the same
respective location within the outline, ensuring minimal variations in
feature position within fixation conditions.We compared the N170 response
to these artificial faces and to house stimuli to ensure proper
face sensitivity. As reported in previous orientation discrimination
tasks (e.g. Itier et al., 2006, 2007) faces were responded to better and
faster than houses and elicited an inversion effectwith better and fasterresponses for upright than inverted faceswhile no such inversion effects
were found for houses. At the ERP level, P1 and N170 ERP components
were delayed for houses compared to faces and the N170 was much
larger for faces than houses (Fig. 2). In addition, although anN170 inversion
effect was found for houses as sometimes reported (e.g. Eimer,
2000) this effectwasmuch larger for faces than houses. All these results
demonstrate proper face sensitivity for our stimuli. The next stepwas to
assess the sensitivity of the N170 to the eyes by comparing the effect of
fixation location on N170 for intact and eyeless faces.