Self-Controlled Continuous Brushing with Vibrotactile Feedback Enhances the Rubber Hand Illusion in Virtual Reality

Feeling ownership of a virtual body in Virtual Reality (VR) enhances the immersion and quality of user experience. Inducing body ownership in VR is mainly based on the Rubber Hand Illusion (RHI) experiment, where watching a rubber hand being stroked while the natural hidden hand is synchronously stroked, induces an illusion of ownership for the rubber hand. Tactile feedback plays a vital role in inducing the RHI in VR. While previous research showed that vibrotactile feedback significantly improves the quality of the illusion, it remains unclear what type of brushing is more effective. In this study, we consider two brushing parameters: (1) self-brushing versus brushing by others and (2) discrete versus continuous brushing. We developed a VR simulation and a haptic sleeve to simulate the RHI through five experimental conditions: control (without haptics), self-discrete, self-continuous, other-discrete, and other-continuous. A total of 85 participants, divided across the 5 experimental conditions, took part in the experiment. The quality of the RHI was assessed using two standard tests, namely proprioceptive drift and an ownership illusion questionnaire. The results indicated that while the control condition (no brushing) showed no significant improvement, all types of brushing resulted in a significant increase in the quality of the illusion. Furthermore, across the four brushing conditions, the self-continuous condition showed a significant increase in the quality of the illusion as compared to the control condition.