ABSTRACT
Traditional accounts of visual agnosia distinguish two disorders: apperceptive and associative agnosia. This chapter examines the factors that lead to the identification advantage for real objects over line drawings in agnosic patients. It examines the role of colour and texture, and demonstrates that both can be effective and for the same reason: both coloured and textured surfaces provide extra information to enable a patient to segment surfaces appropriately. The chapter examines the role of depth and size information, by presenting objects at depths where stereo cues either can or cannot be used, and by either allowing free head movements or by constricting head movements. Depth information in the real world can be conveyed by multiple cues, including binocular disparity, linear perspective, and motion parallax. The data indicates the information about depth and surface shading can contribute to object recognition in cases where edge-based object coding is impaired.
