Comparing Inverted Faces to Upright Faces Using Similarity or Mental Rotation

A major interest of research in face recognition lies in explaining the face inversion effect, in which the recognition of an inverted face is less successful than that of an upright face. However, prior research has devoted little effort to examining how the cognitive system handles comparison between inverted and upright faces. The results of a preparatory experiment and two following experiments support the conclusion that the comparison is based more on visual similarity than on a mental rotation of the inverted face to an upright face. Visual similarity is based on certain elements mutual to the two faces, which resist the transformation of inversion. These elements are symmetric or salient components of the face, such as round eyes or thick lips.