Abstract
Background. A hallmark of face processing is that individual features strongly interact over space, providing an integrated representation of features and their spatial relations. Once the face is inverted, feature spatial interactions are attenuated and mainly local feature information is extracted, leading to strong discrimination and recognition deficits. Face inversion was recently demonstrated to largely stem from the disrupted processing of the vertical spatial relations organising features (e.g. eye height) in a given face, whereas the perception of horizontal relations (e.g. interocular distance) is mildly affected by inversion. Altogether, these findings suggested that upright face perception largely relies on the extraction of vertically-oriented information. Methods. Here we further investigated the prevalence of vertically oriented information in face processing. We measured discrimination performance to upright and inverted faces filtered to preserve Fourier amplitude at vertical and horizontal phase orientations selectively. Results. Upright face discrimination showed differential sensitivity across phase orientation angles. Namely, subjects matched upright face stimuli better when they contained vertically- than when only horizontally-oriented phase information was available. This profile did not merely reflect the orientation spectrum of the stimuli, since it did not replicate when faces were inverted. Conclusion. The present results support the view that upright face discrimination relies on vertically-oriented more than horizontally-oriented information. Follow-up studies will explore whether these phase effects are specific to faces or whether they can be found with other stimulus categories.
The author is grateful to Frederic Gosselin for image analysis assistance.