Observers are remarkably sensitive to point-light displays of human movement. The Superior Temporal Sulcus (STS) and premotor cortex are implicated in the visual perception of point-light human actions and the integration of perceptual signals across modalities. These neurophysiological findings suggest that auditory information might impact visual sensitivity to point-light displays of human actions. Previous research has demonstrated that coincident, action-consistent sounds enhance visual sensitivity to the presence of coherent point-light displays of human movement. Here we ask whether visual detection sensitivity is modulated specifically by the meaningfulness of sounds that are coincident with observed point-light actions. To test this hypothesis, two psychophysical studies were conducted wherein participants detected the presence of coherent point-light walkers in a mask under unimodal or audiovisual conditions. Participants in audiovisual conditions heard either tones or actual footfalls coincident with the seen walkers' footsteps. Detection sensitivity increased when visual displays were paired with veridical auditory cues (footfalls), but not when paired with simple tones. The footfall advantage disappeared when the visual stimuli were inverted. These results suggest that the visual system makes use of auditory cues during the visual analysis of human action when there is a meaningful match between the auditory and visual cues.
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