Avatar-Induced Postural Responses during a Virtual Full-Body Illusion

Abstract

Body ownership over an artificial body can alter perceptual and autonomic responses, but its influence on online postural control remains less understood. We investigated whether ownership-related body-avatar correspondence modulates postural responses to an unexpected change in avatar posture. Thirty-six healthy male participants were randomly assigned to an Embodiment condition, in which body-avatar correspondence was maintained, or a Disruption condition, in which the avatar's arm temporarily moved independently of the participant before the critical event. During a standing virtual-reality session with synchronous visuotactile stimulation, the avatar unexpectedly leaned forward. We introduced Avatar-Induced Postural Response (AIPR), an event-related index of anterior-posterior center-of-pressure displacement following the avatar's movement. Ownership-related questionnaire ratings were higher in the Embodiment condition, whereas self-location-related ratings did not differ between conditions. AIPR was greater in the Embodiment condition and was greater than zero only in this condition. AIPR was also positively correlated with skin conductance responses in the Embodiment condition, but was not associated with questionnaire ratings. These findings suggest that an unexpected change in avatar posture can influence the participant's own postural regulation when ownership-related body-avatar correspondence is maintained. AIPR may provide a complementary behavioral index of a postural-control component of avatar embodiment not fully reflected in explicit subjective reports.