Sex Differences in Visual Half-Field Superiority as a Function of Responding Hand and Motor Demands

Abstract

This chapter discusses the presence of interference of visual, cognitive, and motor processes in divided visual field studies. The comparison of three experiments, which involved identical cognitive tasks but made different demands on motor processes for the reaction, showed the well-documented right-field superiority for verbal stimuli. The increase of motor demands has a dramatic effect on the asymmetry of reaction times (interference effect) of male subjects, but no significant effect on asymmetry in females. The present study is at least able to show that motor demands, which are put upon reactions in a divided visual field study, may have a considerable influence on reaction time asymmetry and that this effect is often different for men and women. Sex differences, therefore, presumably depend upon the fact that the interference effect manifests itself more readily in women than in men. Sex differences in cerebral asymmetry seem to be more complicated than has been supposed, and it may be postulated that sex differences found in lateralization studies––even in those evoked potential studies, where some kind of reaction is required on the part of the subject––are in fact due, at least in part, to differences in intrahemispheric motor influences.