# Behavioural Realism and Its Impact on Virtual Reality Social Interactions Involving Self-Disclosure
## 1 Introduction
### Using Motion Capture for High Behavioural Realism  
Achieving a high level of facial realism typically involves computer analysis of video footage that provides a depth map of the user's face. This includes video processing and algorithms to capture subtle facial gestures with high accuracy [2; 5; 18; 22; 23; 40]. Motion capture that uses video cameras can enable real-time responsiveness, much like sensor-based body motion tracking. This can involve more consistent eye gaze behaviour, mouth and brow movements, and accurate lip synchronisation [35; 40; 41; 42]. Research demonstrates that when interacting with an avatar with a high level of facial realism, the experience can be more engaging, more enjoyable, and more believable when compared to avatars with more restricted facial movements [2; 3; 8; 23; 29; 43].  
Motion tracking of eye gaze can help to enhance the behavioural realism of avatars and potentially improve VR social interactions. Eye gaze is a form of nonverbal communication that indicates where attention is directed and may help to convey interest in the conversation [5; 29; 41; 43; 44; 45]. Accurate capture and replication of eye movements in real-time through motion capture technology enable more natural and consistent eye gaze behaviour in avatars [2; 41; 46]. This enhanced realism may contribute to a stronger sense of social presence and engagement during VR interactions. For instance, [PERSON] et al. [47] found that participants spent approximately 65% of their time looking at their partner's eyes during face-to-face interactions, highlighting the potential benefits of accurate eye gaze behaviour during VR social interactions. Studies have also shown that mutual gaze behaviour can enhance trust, comfort, and closeness in social interactions [26; 48; 49; 50; 51; 52; 53] Realistic eye gaze tracking into avatars could allow VR social interactions to more closely approximate face-to-face conversations, potentially facilitating more natural and engaging exchanges, especially in contexts involving self-disclosure.  
Fully-body motion capture can produce an avatar with a high level of behavioural realism. Motion capture sensors are placed on the body, and movement data are wirelessly transmitted to a receiver connected to a computer [12; 19; 27; 32; 34]. This can be used to animate the movements of an avatar in a more realistic fashion. An avatar with high behavioural realism can help to improve the enjoyment experienced during VR social interactions with avatars by facilitating the expression of nonverbal cues known to improve the quality of social interaction [8; 13; 33; 39; 31].  
Studies that involve VR social interactions often lack full-body motion capture avatars, thus limiting their behavioural realism [6; 8; 35; 39; 54; 55; 56; 57; 58]. Furthermore, many of the studies that include user appraisal of full-body motion capture avatars are not conducted within a social interaction context that resembles a personable face-to-face conversation [2; 24; 28; 30; 37; 53; 57]. Instead, prior studies typically have people rate video play-back of avatars rather than have the user interact with the avatar [3; 6; 8; 11; 17; 21; 59; 60].  
Furthermore, there is an absence of studies that directly compare different levels of motion capture within the same study. This makes it difficult to draw conclusions about how different levels of motion tracking through different motion capture systems can affect social interactions in VR. To address this gap, this study compares two distinct levels of motion capture in the same virtual context involving disclosure. More specifically, participant perceptions of a full-body motion-captured avatar are compared with perceptions of an avatar with limited motion tracking when sharing negative and positive disclosures. By comparing different avatars with different types of motion capture, this study aims to clarify if social VR platforms may benefit from stronger levels of behavioural realism.