Perceptual interference and hemispheric specialization

Two experiments evaluated the effect of stimuli presented at fixation on the recognition of faces or random shapes presented to the left or right visual half-field (VF). Increasing the processing demands of the center stimulus produced a large, linear decrease in recognition from both VFs for both faces and shapes. Recognition of random shapes was decreased more in the right visual field by center digits and in the left VF by center faces and shapes. In addition, interference was found between the VF faces and the center digits to the left of fixation. It was concluded that differences in the processing capacity of the two hemispheres are a function of the verbal-nonverbal nature of the stimuli at a later stage in processing but that the two hemispheres may also differ along other perceptual dimensions at an earlier stage of visual recognition.