Illumination effects in face recognition

How do observers recognize faces despite dramatic image variations that arise from changes in illu­ mination? This paper examines (1) whether face recognition is sensitive to illumination direction and (2) whether cast shadows improve performance by providing information about illumination or hinder performance by introducing spurious edges. In Experiment 1, observers judged whether two sequen­ tially presented faces, illuminated from the same direction or different directions, were the same indi­ vidual or not. Cast shadows were present for half of the observers. Performance was impaired by a change in the illumination direction and by the presence of shadows. In Experiment 2, observers learned to name eight faces under one illumination direction Oeft/right) and one cast-shadow condition (present/absent); they were later tested under novel illumination and shadow conditions. Performance declined for unfamiliar illumination directions, but not for unfamiliar shadow conditions. The rmding that face recognition is illumination dependent is consistent with the use of image-based representa­ tions. The results indicate that face recognition processes are sensitive to either the direction of light­ ing or the resultant pattern of shading, and that cast shadows can hinder recognition, possibly by mask­ ing informative features or leading to spurious contours.