Higo, K. | bioRxiv Science

bioRxiv2026

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

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.

neuroscience↗

bioRxiv2026

Avatar facial expressions enhance social presence and inter-brain synchronization in virtual reality

Virtual reality (VR) has become a prominent medium for computer-mediated social interaction, yet the psychological and neural mechanisms underpinning avatar-mediated communication remain insufficiently understood. This study investigated how dynamically modulated avatar facial expressions shape interpersonal interaction in VR. Pairs of participants engaged in a collaborative creativity task while interacting via avatars whose facial expressions were either amplified, natural, or expressionless. We collected subjective measures of body ownership, social presence, and interpersonal attraction, while simultaneously recording neural activity using functional near-infrared-spectroscopy-based hyperscanning to assess inter-brain synchrony (IBS). Avatars displaying facial expressions, particularly amplified ones, significantly enhanced body ownership, social presence, and interpersonal attraction compared to expressionless avatars. At the neural level, visible avatar facial expressions were associated with IBS in the right temporo-parietal junction (TPJ) and the dorsolateral prefrontal cortex (dlPFC), regions that are commonly implicated in social-cognitive processes such as mentalizing and executive control. Although task performance did not differ across conditions, social presence was positively correlated with creative performance, suggesting that psychological connectedness supports collaborative creativity. Together, these findings indicate that avatar facial expressivity functions as a critical nonverbal social cue that facilitates affective and cognitive alignment between interaction partners. By linking subjective experience with inter-brain neural dynamics, this study provides empirical guidance for the design of virtual environments that promote social engagement and effective collaboration.

neuroscience↗