Investigations of visual field asymmetries.

It was suggested that in addition to its value as a research tool, there may be practical applications of the divided visual field technique. If it is to be used as a method of investigating individual oases in order to assess hemispheric lateralization of function, it must be fully understood. The relative merits of the three major theories of visual field asymmetries were reviewed. A series of ten experiments was performed in which stimuli were presented tachistoscopically to the right and left visual fields. Both verbal stimuli in the form of words and single letters and nonverbal stimuli in the form of shapes, drawings and faces were employed. A variety of problems were considered. The relationship of the serial-parallel processing dichotomy to the left and right hemispheres was considered and not believed to be useful. The distinction between the hemispheres was in terms of visual-verbal processing, although this separation of functioning was not as clearcut as has been thought. It was concluded that the direct access theory was the most adequate explanation of the data, although the results may be partially influenced by scanning and attentional phenomena. Load-sharing between the hemispheres was discussed.