The Virtual Rubber Hand Illusion: Moving in the Right Direction?

Abstract

The Rubber Hand Illusion is an illusion in which
visual cues of stimulation on a fake hand are combined with
synchronous tactile cues on a participant’s hand, which can
induce a sense of bodily ownership of the fake hand. This
technique does not facilitate synchronous movement of the
hands, and asynchronous stimulation or movement can break the
illusion, thereby limiting potential benefits that bodily ownership
may have in practical applications such as telerobotic control.
This study aims to quantify to what extent a Virtual Reality
headset with hand tracking capabilities can be used to evoke a
rubber hand illusion, and to what extent the illusion strength
maintains during voluntary hand movement. Twelve subjects
were randomly presented with three conditions; the classic Rubber
Hand Illusion (RHI), serving as a baseline for comparison,
the static Virtual reality Rubber Hand Illusion (VRHI), the
virtual reality equivalent of the original experiment, and the
moving Virtual reality Rubber Hand Illusion (mVRHI), where
participants’ voluntary hand movements were tracked using
motion controllers, to generate simultaneous virtual hand motion.
Illusion strength was quantified subjectively, by a 27-question
questionnaire adapted from literature, and objectively, by measuring
proprioceptive drift; the distance between perceived hand
location and actual hand location. It was hypothesized that VRHI
and mVRHI would increase the strength of the illusion, compared
to RHI. A significant increase in proprioceptive drift was found
between the RHI and VRHI conditions. Questionnaire scores
in the ownership category were significantly higher for VRHI,
and the control category showed higher scores for mVRHI. In
conclusion, a higher embodiment was achieved during VRHI, but
mVRHI did not improve upon VRHI as expected.