Face inversion disproportionately impairs the perception of vertical but not horizontal relations between features

Upside-down inversion disrupts the processing of spatial relations between the features of a face, while largely preserving local feature analysis. However, recent studies on face inversion failed to observe a clear dissociation between relational and featural processing. To resolve these discrepancies and clarify how inversion affects face perception, the authors monitored inversion effects separately for vertical and horizontal distances between features. Inversion dramatically declined performance in the vertical-relational condition, but it impaired featural and horizontal-relational performance only moderately. Identical observations were made whether upright and inverted trials were blocked or randomly interleaved. The largest performance decrement was found for vertical relations even when faces were rotated by 90 degrees. Evidence that inversion dramatically disrupts the ability to extract vertical but not horizontal feature relations supports the view that inversion qualitatively changes face perception by rendering some of the processes activated by upright faces largely ineffective.