Virtual humans in virtual reality: a scoping review on sociability, fidelity, and expression

Introduction Virtual reality (VR) systems have evolved significantly over the past decade, enabling immersive experiences with enhanced realism and interactivity. This has motivated an interest in socially oriented applications. As user proxies, Virtual Humans (VHs) play essential roles in such applications. However, despite technological advancements, achieving realistic, expressive, and socially responsive VHs continues to present design and implementation challenges. In this scoping review, we present the state-of-the-art of VR VHs, examining the impact of VHs on the user experience. Methodology We reviewed 59 papers retrieved from five databases across three core themes: the implementation and impact of VH facial expressions, the impact of VH fidelity on the user experience, and the influence of VHs on human emotion and social engagement in VR. In addition, we categorized the methodologies of the reviewed studies, detailing the nature of participant interactions and the measurements taken to derive the results. Results The synthesis of the examined studies indicates that both the social context (e.g., collaborative work vs. solo tasks) and the virtual environment (realistic office vs. fantastical world) significantly influence VH design decisions, such as the appropriate level of realism and emotional expressiveness. Discussion Our review highlights the relation between social engagement, fidelity and expressiveness. We offer a set of guidelines for researchers and developers aimed at optimizing VH design to enhance user experience in VR.