The dominance of one modality over the respective other plays an important role in dealing with conflicting situations between sensory streams. The ventriloquism illusion provides striking evidence for a visual dominance in the spatial domain. So far, perception of spatially disparate information has been mainly studied with stationary objects focusing on frontal directions. However, mutual influences of vision and audition in the periphery are scarcely investigated.
The present free-field study investigated crossmodal interactions during audio-visual motion perception in both frontal and peripheral spatial regions. In randomly presented trials moving audio-visual stimuli were congruent or differed with respect to their final position. Subjects were instructed to selectively attend to either the visual or the acoustic part of the stimulus and to indicate the perceived final position.
The data suggest that in frontal regions the perception of acoustic motion is shifted to a greater extent towards the visual stimulus than vice versa. However, at peripheral positions this mutual influence is inverted, i.e. the auditory modality rather biases visual motion perception. The results are in accordance with the information reliability hypothesis stating that the modality which provides more beneficial information contributes to the perception of a stabilized object.