Effects of temporal asynchrony and stimulus magnitude on competitive audio-visual binding.

When making decisions as to whether or not to bind auditory and visual information, temporal and stimulus factors both contribute to the presumption of multimodal unity. In order to study the interaction between these factors, we conducted an experiment in which auditory and visual stimuli were placed in competitive binding scenarios, whereby an auditory stimulus was assigned to either a primary or a secondary anchor in a visual context (VAV) or a visual stimulus was assigned to either a primary or secondary anchor in an auditory context (AVA). Temporal factors were manipulated by varying the onset of the to-be-bound stimulus in relation to the two anchors. Stimulus factors were manipulated by varying the magnitudes of the visual (size) and auditory (intensity) signals. The results supported the dominance of temporal factors in auditory contexts, in that effects of time were stronger in AVA than in VAV contexts, and stimulus factors in visual contexts, in that effects of magnitude were stronger in VAV than in AVA contexts. These findings indicate the precedence for temporal factors, with particular reliance on stimulus factors when the to-be-assigned stimulus was temporally ambiguous. Stimulus factors seem to be driven by high-magnitude presentation rather than cross-modal congruency. The interactions between temporal and stimulus factors, modality weighting, discriminability, and object representation highlight some of the factors that contribute to audio-visual binding.