Evidence for Auditory-Visual Processing Specific toBiological Motion

摘要

Biological motion is usually associated with highly correlated sensory signals from more than one modality:an approaching human walker will not only have a visual representation, namely an increase in the retinalsize of the walker's image, but also a synchronous auditory signal since the walker's footsteps will growlouder. We investigated whether the multisensorial processing of biological motion is subject to differentconstraints than ecologically invalid motion. Observers were presented with a visual point-light walker and/or synchronised auditory footsteps; thewalker was either approaching the observer (looming motion) or walking away (receding motion). A scram-bled point-light walker served as a control. Observers were asked to detect the walker's motion as quicklyand as accurately as possible. In Experiment I we tested whether the reaction time advantage due to re-dundant information in the auditory and visual Modality is specific for biological motion. We found noevidence for such an effect: the reaction time reduction was accounted for by statistical facilitation for bothbiological and scrambled motion. In Experiment 2, we dissociated the auditory and visual information andtested whether inconsistent motion directions across the auditory and visual modality yield longer reactiontimes in comparison to consistent motion directions. Here we find an effect specific to biological motion:motion incongruency leads to longer reaction times only when the visual walker is intact and recognisableas a human figure. If the figure of the walker is abolished by scrambling, motion incongruency has no effecton the speed of the observers' judgments. In conjunction with Experiment I this suggests that conflictingauditory–visual motion information of an intact human walker leads to interference and thereby delayingthe response.