Visual-auditory interactions in sensorimotor processing: saccades versus manual responses

Reaction times (RTs) to bimodal (visual and auditory) stimuli were examined using 3 different response systems: saccades, directed manual responses, and simple manual responses. The observed levels of intersensory facilitation exceeded race model predictions and therefore support summation (coactivation) models of bimodal processing. However, response-dependent differences suggest that the processing of bimodal targets also depends on the relevant sensorimotor pathways and requirements of the task. Coactivation of response mechanisms might account for the effects found using simple RTs. The results for saccades are consistent with known patterns of auditory-visual convergence in the oculomotor system.