Visual Perceptual Organization: Lessons From lesions

The visual world consciously perceived is very different from the chaotic Juxtaposition of different colors and shapes that stimulate the individual retinal receptors. Objects are seen as detached and separable from adjacent objects and surfaces despite the fact that parts of a single object may be spatially Of temporally discontinuous, and have different colors or even transect several different depth planes. Additionally. because most surfaces are opaque, portions of objects are routinely hidden from View, and, as we move around. surfaces continually undergo occlusion and fragmentation. As IS apparent from this description. the objects of phenomenal perception are not given in any direct way in the retinal image. Some Internal processes of organization must clearly be responsible, then. for producing a Single, coherent percept. Exactly what these processes are remains poorly understood despite the roughly 100 years since the Gestalt psychologists first articulated the principles of perceptual organization. Although the Gestalt work on perceptual organization has been widely accepted as identifying crucial phenomena of perception. there has been, until the last decade or so, relatively little theoretical and empirical emphasis on perceptual organization with a few exceptions. And, to the extent that progress has been made, there still remain many open questions. In this chapter, we explore some of these open Issues in light of data we have obtained through a series of neuropsychological Investigations with individuals who are impaired in perceptual organization following brain damage, hence the title of this chapter.