1 Hemispheric Asymmetry for Components of Visual Information Processing

The left and right cerebral hemispheres of humans do not handle all aspects of visual information processing with equal ability. Instead, each hemisphere is better able than its partner to handle certain components of processing. Although there continues to be uncertainly surrounding exactly what the relevant components are, it has proved useful to decompose tasks into those processing components that have been hypothesized by contemporary models of perception, cognition, and action. In this chapter, I review some of what this componential approach has revealed about hemispheric asymmetry for visual information processing. In keeping with the general theme of the book, this review considers relationships among various models of visual laterality, the major questions that remain to be answered before we have a truly comprehensive model of hemispheric asymmetry for components of visual processing and the methodologic implications for the study of perceptual asymmetry. The chapter begins with a brief discussion of what I call a componential approach to the study of hemispheric asymmetry. This is followed by a review of research that demonstrates hemispheric asymmetry for each of three processing distinctions that come from contemporary theories of visual information processing: (I) global vs. local processing, (2) low vs. high visuospatial frequencies, and (3) coordinate vs. categorical spatial relationships. I then discuss how these three processing distinctions may be related to one another and consider the possibility that hemispheric asymmetries of all three types may be different manifestations of the same thing. This is followed by a discussion of certain parallels between hemispheric asymmetry for components of visual processing and hemispheric asymmetry for components of auditory processing and for certain aspects of motor activity. Much of the research presented here involves the study of perceptual asymmetries in neurologically intact persons. This being the case, the chapter ends with a brief discussion of the methodologic implications of the research on hemispheric asymmetry for components of visual processing.