Recognition impairments and face imagery.

We investigated face imagery for H.J.A. and P.H., who experience profound difficulties in recognising familiar faces. H.J.A.'s problems involve a perceptual impairment that compromises the integration of features into a coherent representation, and he does not show covert recognition of faces in indirect tests. In contrast, P.H. has shown extensive covert recognition effects, leading to the suggestion that his deficit occurs at a higher level of visual processing than H.J.A.'s. H.J.A. and P.H. were given tasks intended to explore their ability to answer questions that depended on imaging single faces, and on configuration-based or feature-based comparisons of imaged sets of three faces. For all of these face imagery tasks, P.H.'s overall performance was severely impaired. H.J.A., though, showed preserved face imagery when imaging single faces and when making feature-based comparisons between imaged faces. However, when configuration-based comparisons were demanded H.J.A. also showed a severe and stable impairment of face imagery. These observations are inconsistent with the idea that face recognition impairments have a unitary underlying cause and vary only in severity. Instead, they imply multi-stage causation, with the nature of consequent impairments of face imagery being determined by the level at which the recognition deficit arises.