The Sense of Embodiment in Augmented Reality: A Third Hand Illusion
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In Augmented Reality (AR) people can interact with virtual objects, but there is a problem if these objects are too far away to reach. A solution could be to add a virtual hand, which can be used alongside the real hands, and can cover a larger distance. Ideally, this hand should be experienced like a real hand to make the interaction more natural. This experience is called the Sense of Embodiment (SoE). From the literature, we know that it is possible to induce the SoE in Virtual Reality (VR) over extended bodies, thus we can speculate that it should also be possible to induce the SoE in AR, where the real body is visible. Yet, there are fundamental differences between AR and VR, i.e. the visual presence of the real body in AR compared to a virtual body or no body in VR. Thus, we could not exactly copy the setups used in VR research to investigate our theory. Therefore we did three pilot studies to research visual-motor feedback, visual-tactile feedback and the visual presence of the real arm. We found two main factors to take into account, which are the visual appearance of the virtual hand and the congruency of the multimodal feedback. In a detailed experiment, we show that despite a signi?cant effect of visual-tactile and visual-motor feedback, it is surprisingly not possible to induce ownership with our setup, due to the uncanny valley effect. We therefore conclude that, if at all, such ownership in AR may only appear if the virtual hand appears either very realistic or very abstract. Our results also show that the visual presence of the real hand does not affect the sense of agency, and it prevents a shift in sense of location, but caused some participants to experience that their left hand was in two locations simultaneously. This is promising as it may suggest that ones perception of location can be split, which could be the focus of a follow-up study.