Feature-location effects in the Thatcher illusion

Abstract

Face perception is impaired for inverted images, and a prominent example of this is the Thatcher illusion: ''Thatcherized'' (i.e., rotated) eyes and mouths make a face look grotesque, but only if the whole face is seen upright rather than inverted. Inversion effects are often interpreted as evidence for configural face processing. However, recent findings have led to the alternative proposal that the Thatcher illusion rests on orientation sensitivity for isolated facial regions. Here, we tested whether the Thatcher effect depends not only on the orientation of facial regions but also on their visual-field location. Using a match-to-sample task with isolated eye and mouth regions we found a significant Feature × Location interaction. Observers were better at discriminating Thatcherized from normal eyes in the upper compared to the lower visual field, and vice versa for mouths. These results show that inversion effects can at least partly be driven by nonconfigural factors and that one of these factors is a match between facial features and their typical visual-field location. This echoes recent results showing feature-location effects in face individuation. We discuss the role of these findings for the hypothesis that spatial and feature tuning in the ventral stream are linked.