Designing for Hand Ownership in Interaction with Virtual and Augmented Reality
Tiare Feuchtner · 2018
This thesis explores the body ownership illusion during interaction in virtual and augmented reality; in particular, how the body ownership illusion can be leveraged to overcome the limitations of our physical bodies and to create more efficient and engaging interactions. Body ownership is the feeling that we inhabit a physical body through which we experience and interact with the world. The conviction that your physical hand is, in fact, your own hand is an example of body ownership. Under certain conditions, this feeling can also be elicited by an artificial body or body part (e.g., a rubber hand or virtual hand), which is then known as the body ownership illusion. The research questions presented in this thesis were explored with two independent prototypes: the first consisting of an augmented reality system and the second providing a virtual reality experience. The state-of-the-art for immersive virtual reality involves interaction with the virtual world through controllers which we perceive as tools hovering in mid-air. We cannot see our hands gripping these tools, nor do we have any other indicators of our body in our peripheral vision or through the presence of shadows. This ghostly, body-less state is unnatural, and a constant reminder that the world we see around us is not real. Our sense of presence is limited if we do not have a body that inhabits part of the environment we perceive. In augmented reality applications on the other hand, we typically perceive our own body as part of the real world and can sometimes use our physical hands to manipulate virtual content. However, in contrast to virtual hands, our physical hands cannot be flexibly adapted for a specific task (e.g., to extend our reach). Hence, I explored how we can create a virtual body representation to which the user feels strongly connected through the body ownership illusion. I argue that this inherently changes the quality of the interaction; while traditionally the screen forms a clear boundary between the real and the virtual world, the illusion of owning a virtual body moves this border into our own minds. In other words, a virtual body representation may seem just as real to us as our physical bodies. The findings presented in this thesis show that we can control an unnaturally long virtual arm that we perceive as part of our body. Furthermore, we can feel body ownership of a virtual hand that appears to be reaching towards an overhead target, while our physical hand rests comfortably at waist-level. We may even feel body ownership of a very unrealistic, disconnected virtual hand, if it follows our movements naturally. The results thus indicate that our mental body representation may be more malleable than was previously believed. Consequently, while most approaches to interaction design attempt to modify the virtual world or tools with which we interact, we can instead augment the body we interact through - or at least our mental image thereof.