Three Techniques for Enhancing Emotional Expression on Embodied Avatar Face in VR

People often attempt to mask their true emotions through deliberate facial expressions, but such efforts are not always successful. In contrast, emotional concealment could be more easily achieved in Virtual Reality (VR) when appropriate functionalities are available. This study introduces three techniques in VR that enable users to manually adjust emotional facial expression while still reflecting real-time facial tracking results. The Ekman (Ek) technique allows users to select six discrete emotions via button interaction, while the Scrollable-Ekman (SEk) technique extends this by allowing users to scale the intensity of the selected emotion. The Arousal-Valence (AV) technique offers nuanced control within a two-dimensional arousal-valence space. We evaluated these techniques against a baseline condition that synchronizes users' natural facial expressions, focusing on the expression of happiness, sadness, and anger. In most measurements, the Ek and SEk showed better results compared to the baseline and the AV techniques. Notably, the SEk technique was particularly effective in enhancing hedonic quality. During the free-flowing conversation, the most critical factor was the timely and well-synchronized coordination between speech and controlled facial expressions. Participant satisfaction also varied by usage style: those who tried to use the techniques continuously and naturally to mimic real-life communication reported lower satisfaction, while those who used them occasionally for playful or exaggerated expressions tended to report higher satisfaction.