The Sense of Embodiment in Augmented Reality: A Third Hand Illusion
Summary
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.