Distinguishing the cause and consequence of face inversion: the perceptual field hypothesis

I published a critical review of the face inversion effect (Rossion, 2008) that triggered a few reactions and commentaries by colleagues in the field (Riesenhuber & Wolff, 2009; Yovel, in press). Here, I summarize my original paper and attempt to identify the source of both the agreements and disagreements with my colleagues, as well as other authors, regarding the nature of the face inversion effect. My view is that the major cause of the detrimental effect of inversion on an observer's performance at individual face recognition is the disruption of a perceptual process. This perceptual process is makes and observer see the multiple features of a whole individual upright face at once. It also makes the percept of a given facial feature highly dependent on the location and identity of the other features in the whole face. The perceptual process is holistic because it is driven by a holistic face representation, derived from visual experience. Hence, an inverted face cannot be perceived holistically: the perceptual field of the observer is constricted for inverted faces, each facial feature having to be processed sequentially, independently, i.e. over a smaller spatial window than the whole face. Consequently, it is particularly difficult to perceive diagnostic cues that involve several elements over a wide space on an inverted face, such as long-range relative distances between features (e.g., relative distance between eyes and mouth), or diagnostic cues that are located far away from usual gaze fixation (e.g., mouth-nose distance or mouth shape when fixating between the eyes). These difficulties are mere consequences of face inversion--the cause being a loss of holistic perception--, and it does not follow that relative distances between internal features are necessarily particularly important to recognize faces, that they should be labeled "configural", or should be given a specific status at the representational level. I argue that distinguishing the cause and consequence(s) of face inversion this way can provide a parsimonious and yet complete theoretical account of the face inversion effect.