Contrast Negation Impairs Sorting Unfamiliar Faces by Identity: A Comparison With Original (Contrast-Positive) and Stretched Images.

Recognition of unfamiliar faces is difficult in part due to variations in expressions, angles, and image quality. Studies suggest shape and surface properties play varied roles in face learning, and identification of unfamiliar faces uses diagnostic pigmentation/surface reflectance relative to shape information. Here, participants sorted photo-cards of unfamiliar faces by identity, which were shown in their , , and forms, to examine the utility of diagnostic shape and surface properties in sorting unfamiliar faces by identity.