Expansion of Detection Thresholds for Hand Redirection using Noisy Tendon Electrical Stimulation

Abstract

To increase the flexibility of haptic feedback in virtual reality (VR), hand redirection (HR) has been proposed to shift the hand's virtual position from its actual position. To expand the range of HR applications, a method to broaden the detection threshold (DT), which is the maximum amount of shift that can be applied without the user noticing, is required. Multisensory integration studies have revealed that the reliability of senses affects the weight of integration. To expand the DTs of HR, we propose a method to increase visual dominance in the integration of vision and proprioception by introducing noise to the latter, thereby decreasing its reliability through weak Gaussian white noise electrical stimulation ($\sigma$=0.5mA). The results of a user study comprising 22 participants (11 women and 11 men) confirm that noisy electrical stimulation significantly expands the DTs of HR with the mean range of DTs ($R_{DT}$) was 20.48° (SD =7.90) with electrical stimulation and 19.15° (SD =7.11) without electrical stimulation. Interestingly, this effect was only observed in women. The average $R_{DT}$ for men was 15.36° (SD =6.13) and 15.18°(SD=5.58), whereas that for women was 25. 61°(SD=5.89) and 23.12°(SD=6.21), with and without electrical stimulation, respectively. Electrical stimulation was mostly tolerable for the participants and did not affect embodiment or presence ratings. These results suggest that expansion of the DT without disturbing the user's VR experience is feasible.