Illumination effects in face recognition

How do observers recognize faces despite dramatic image variations that ari se from changes in illumination? This paper examines (1) whether face recog nition is sensitive to illumination direction and (2) whether cast shadows improve performance by providing information about illumination or hinder p erformance by introducing spurious edges. In Experiment 1, observers judged whether two sequentially presented faces, illuminated from the same direct ion or different directions, were the same individual or not. Cast shadows were present for half of the observers. Performance was impaired by a chang e in the illumination direction and by the presence of shadows. In Experime nt 2, observers learned to name eight faces under one illumination directio n (left/right) and one cast-shadow condition (present/absent); they were la ter tested under novel illumination and shadow conditions. Performance decl ined for unfamiliar illumination directions, but not for unfamiliar shadow conditions. The finding that face recognition is illumination dependent is consistent with the use of image-based representations. The results indicat e that face recognition processes are sensitive to either the direction of Lighting or the resultant pattern of shading, and that cast shadows can kin der recognition, possibly by masking informative features or leading to spu rious contours.