Abstract
Can auditory input influence the sensory processing of visual information? Many studies have reported cross-modal enhancement in visual tasks, but the nature of such gain is still unclear. Some authors argue for ‘high-order’ expectancy or attention effects, whereas others propose ‘low-order’ stimulus-driven multisensory integration. The present study applies a psychophysical analysis of reaction time distributions in order to disentangle sensory changes from other kind of high-order (not sensory-specific) effects. Observers performed a speeded simple detection task on Gabor patches of different spatial frequencies and contrasts, with and without accompanying sounds. The data were adjusted using chronometric functions in order to separate changes is sensory evidence from changes in decision or motor times. The results supported the existence of a stimulus unspecific auditory-induced enhancement in RTs across all types of visual stimuli, probably mediated by higher-order effects (eg, reduction of temporal uncertainty). Critically, we also singled out a sensory gain that was selective to low spatial frequency stimuli, highlighting the role of the magno-cellular visual pathway in multisensory integration for fast detection. The present findings help clarify previous mixed findings in the area, and introduce a novel form to evaluate cross-modal enhancement.