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.