chapter  5
34 Pages

Methodological Constraints on Neuropsychological Studies of Face Perception in Normals

By virtue of the anatomical property of the visual system whereby information presented in one lateral visual field is transmitted along neural pathways to the occipital and tectal regions of the contralateral hemisphere, the methods of experimental psychology can be, and have been, applied in a neurological context, providing a strategy to extend our understanding of the functions of the two intact cerebral hemispheres. Initially, research on cerebral lateralization of functions in normals was entirely contingent on findings from the neurological population, and early evidence of concordance between results from normal and brain-damaged subjects (e.g., Bryden, 1965; Kimura, 1966) validated the lateral tachistoscopic technique as a means of studying functional asymmetry in the intact brain. In this context, the accumulation of evidence during the 1960s of a critical role of the right hemisphere (RH) in the processing of faces (Benton & Van Allen, 1968; De Renzi & Spinnler, 1966; Hecaen & Angelergues, 1962; Milner, 1968; Newcombe, 1969; Warrington & James, 1967) prompted the investigation of this hemisphere functional specialization in normal subjects. Yet, the very first study to examine this issue failed to confirm the prediction. Rizzolatti, Umilta, and Berlucchi (1970), using sketches of faces of famous persons presented in the right visual field (RVF) or the left visual field (L VF), found that the two hemispheres were equally efficient at processing physiognomies. The following year, however, two independent studies concurred with the neurological evidence of a RH superiority in the processing of faces. Rizzolatti, Umilta, and Berlucchi (1971), in a go/no-go manual reaction time (RT)

task with photographs of unfamiliar faces, found shorter latencies to LVF presentations, as did Geffen, Bradshaw, and Wallace (1971) in a same-different manual RT task, with Identikit faces.