Abstract
Recognition of a human face relies on successful matching of the features and their spatial arrangement to a stored representation. Yet our ability to do this is greatly impaired when a face is inverted. This is likely associated with the decrease in responses to spatial differences in fusiform face area, a face sensitive region of the brain, when a face is inverted (Kanwisher, Tong, & Nakayama, 1998). Despite this, perceptual tasks such as the estimation of intraocular distance or eye to mouth distance are unaffected by inversion (Schwanniger, 2003). We asked whether face shape discrimination involving comparisons between faces that were elongated or otherwise geometrically deformed is impaired by inversion. We found that face shape discrimination is not subject to the traditional face inversion effect. This is true whether the comparisons are simultaneous or sequential. We conclude that orientation does not affect our ability to perceive spacing information. We suggest that the face inversion effect observed with recognition results from an incompatibility between the orientation of the observed face and its memory trace. As suggested by Rock (1974), the processes involved with mental rotation may be overtaxed when attempting to recognize an inverted face, but mental rotation is unnecessary for face shape discrimination.
This research was supported by NIH grant EY01711.