Reaction time asymmetry through bilateral versus unilateral stimulus presentation.

Previous research indicates that bilateral stimulation of the visual fields results in larger asymmetry than unilateral stimulation. However, the research has largely been limited to percentage correct studies. Here, three experiments employ reaction time (RT) measures, and show that the bilateral advantage generalizes to RT, and across spatial and verbal stimulus materials (bargraphs, letters, and words). Visual field differences average about six times larger with bilateral than with unilateral presentation. Beyond promising increased power to detect hemispheric differences, the results argue against structural and attentional models of behavioral asymmetry and support a dynamic (hemispheric interaction) model.