My research explores how to develop more influential interactive systems and how to effectively and efficiently enhance human abilities using immersive eXtended Reality (XR)—Virtual/Augmented/Mixed reality (VR/AR/MR), while pursuing better understanding of human perception and behavior in (social) interactions with/through virtual entities, in a broad scope of Human-Computer Interaction (HCI) and User Experience (UX). For example, I investigate the effects of embodied Virtual Humans (VHs) with coherent and plausible behaviors interacting with the surrounding physical environment on the sense of social presence with the VH and the trustworthiness of it.