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.