Buttock Skin Stretch: Inducing Shear Force Perception and Acceleration Illusion on Self-motion Perception

This study presents a new concept of buttock skin stretch to induce the perception of shear force while sitting. Skin stretch is a potential approach to deliver kinesthetic information by cutaneous stimuli with a compact and portable device. We first introduce the buttock skin stretch approach for a virtual motion platform to enhance the experience of self-motion acceleration. We developed a single degree-of-freedom skin stretch device to deform the buttock skin in the lateral direction of the frontal plane. To deal with the shape difference of buttocks, the initial position of the sliding contactors was calibrated with the buttock pressure distribution on the seat. We investigated the relationship between the contactor displacement and the perceived shear force on each lateral side. The estimated magnitudes of the perceived force showed a monotonically increasing trend corresponding to the skin stretch displacement on each side. The observed similarity between the left and right sides suggests the good reproducibility of the proposed method. We also investigated the bias effect of the buttock skin stretch to the perceived acceleration of self-motion, which was induced by the vection illusion presented with an optical flow. The results of the magnitude estimation suggest that skin displacement of 9 mm biased the perceived acceleration more than that of 3 mm displacement. These findings suggest that the shear force induced by the buttock skin stretch can enhance the perception of self-motion.