ABSTRACT
Research with normal subjects using lateral tachistoscopic techniques has shown that some visual tasks may be performed better if the stimuli are presented in the visual field to the left of fixation (LVF) whereas other tasks are performed better if stimuli are presented in the visual field to the right of fixation (RVF). Because the visual pathways arising from the temporal hemiretinas in humans pass directly to the ipsilateral cerebral hemisphere and the pathways arising from the nasal hemiretinas project to the contralateral cerebral hemisphere (Davison, 1972), visual stimuli that are presented in the LVF, are, initially, represented in the right hemisphere (RH) of the brain. Stimuli presented in the RVF, on the other hand, are represented in the left cerebral hemisphere (LH). Thus, the dependence of performance on visual-field presentation has been assumed to reflect information-processing asymmetries between the two cerebral hemispheres. The precise way in which to characterize hemispheric differences in processing, has led to a proliferation of models that attempt to categorize asymmetries in terms of a high-level task dichotomy (e.g., analytic/holistic or verbal/visuospatial) (Bradshaw & Nettleton, 1981; and reviews in Beaton, 1985; Cohen, 1982; Hardyck, 1986; Sergent, 1983).
