Hemispheric Lateralization of Visual Perception

Abstract

The existence of hemispheric asymmetry of function with special reference to the function of the right temporal lobe was investigated. Two types of material (nonsense words and nonsense figures) were selected on the basis of low association (a’) value, to be presented to three groups of subjects, non-brain-damaged, left temporal and right temporal. The subjects were tested in a tachistoscopic like task in which the material to be identified was presented at varying exposure durations. Identifications were made by selecting the appropriate item from a visual array of test and non-test items. Prior to testing the subject was given some experience with half of the test items. Each subject was tested on two occasions, once with the words and once with the figures. The left temporal subjects displayed a deficit in the identification of the words and the right temporal subjects displayed a deficit in the identification of the figures. Both experimental groups were inferior to the non-brain-damaged group. Prior experience with some of the test material enhanced performance but contrary to that predicted this effect was not related to the type of material and the groups. These results indicated the probable existence of a hemispheric asymmetry of function independent of the sensory modality involved. This asymmetry was discussed in light of suggestions that the right temporal lobe is responsible for non-verbal functioning and the left temporal lobe for verbal functioning.