Comparing Thompson's Thatcher effect with faces and non-face objects

Abstract

The classical Thatcher effect (TE) is experienced when global inversion of a face makes it difficult to notice the local inversion of its parts (Thompson, 1980). The TE can be quantified by comparing the ease with which observers compare a normal and locally transformed image, when both images are shown upright versus inverted. Here we compared the classical TE for images of adult faces to a wide variety of other categories, including grimacing faces, baby faces, animal faces, buildings, scenes, and various types of letter-strings. If the TE reflects a special form of configural processing for faces, faces should show a much larger TE than all other categories. Error rates revealed larger TEs for letter-strings over all other categories. Within the letter-string categories, words showed a larger TE than non-words and low frequency words revealed a larger TE than high frequency words. Within the face categories, adult, grimacing, and baby faces showed comparable TEs whereas animal faces showed the largest TE. For objects, we observe TEs for all categories, but at smaller magnitudes. Our results suggest the TE is not exclusive to faces - it does not appear to uniquely depend on factors such as expertise or the grotesque appearance of the transformation.