Cerebral hemispheres serve as two channels for visual information processing

Abstract

Grid patterns or eve trigrams were presented tachistoscopically in the left or right visual fields or concurrently in both visual fields. There were fewer errors in identifying both grids and eves when a grid on the left was paired with a eve on the right than when a eve on the left was paired with a grid on the right. The result indicated that when each hemisphere received the type of stimulus material, spatial or verbal, for which its function was specialized, they served as separate channels and processing accuracy was maximal. Experimental research on laterality differences in the perception of visual and auditory stimuli indicates a basic assymetry in cerebral hemispheriC functioning (Allard, 1972; Milner, 1971; White, 1969). The right hemisphere is specialized for processing nonverbal or spatial material whereas the left hemisphere processes mainly verbal material. Owing to contralateral representation in the central nervous system, stimuli presented in the left visual field are directed to the right hemisphere, and stimuli in the right visual field are directed to the left hemisphere. Hemispheric assymetry is demonstrated in experiments which involve presenting spatial or verbal stimuli in the left or right visual fields. Reaction times for comparison between the physical or spatial aspects of letters are much faster when the letters are presented in the left visual field. But for comparisons between the verbal or nominal aspects, reaction times are faster when the letters are presented in the right visual field (Cohen, 1972; Geffen, Bradshaw, & Nettleton, 1972). In the present experiment, verbal stimuli were presented in one visual field while spatial stimuli were simultaneously presented in the other. It was expected that accuracy of identification of the stimuli would be greater for verbal stimuli in the right visual field and spatial stimuli in the left than for the converse situation. That is, processing accuracy should be maximal when each hemisphere analyzes stimuli appropriate to its function.