Examination of Perceptual Interaction of Illusions Created by Illusion-inducing System Using a Laptop and Vibrator
Ryosuke AKASHI, Kazuhiro MATSUI, Hiroaki HIRAI, Atsushi NISHIKAWA, Fuminari KANEKO
Vol. 14 (2025) p. 117-125
Kinesthetic illusion induced by visual stimulation (KINVIS) is a phenomenon in which a virtual kinesthetic perception is induced by watching virtual limb movements mimicking actual limb movements. Recently, the KINVIS has been used for the rehabilitation of patients with stroke. Visual immersion is thought to be essential to achieve the KINVIS. Existing KINVIS rehabilitation equipment uses large devices, such as enclosed boxes or head-mounted displays, to improve immersion. To conveniently improve the effectiveness of the KINVIS, we combined it with the rubber hand illusion (RHI) and pulling illusion (PI), which can be induced by simple equipment. The RHI occurs when a fake hand is perceived as a real hand once tactile and visual stimuli are synchronized. The PI occurs when asymmetric vibrations induce the user to sense as though his/her body is being pulled. We developed a system that induces these three illusions by using an upper limb avatar on a laptop personal computer (PC) display and a vibrator. Participant placed the upper limb behind the laptop PC display overlapping with the image of the upper limb avatar. In this setup, participant experienced combinations of the illusions by watching the motion of the upper limb avatar and the vibrator object, and sensing the vibrations of the vibrator. Two evaluation indices; namely, sense of ownership (SoO) and sense of body motion (SoBM), were employed. SoO quantified the degree of recognition of a virtual body as one’s own, while SoBM quantified the degree of feeling that the body had moved. We conducted a questionnaire on the direction and strength of the participant’s SoBM and SoO. Results showed that the RHI increased SoO for the avatar, considered to enhance immersion, which in turn increased the effect of the KINVIS. However, there was no positive interaction between the PI and KINVIS; when the PI and KINVIS were in opposite directions, tactile and visual information did not integrate, and the KINVIS decreased the effect of the PI. The main contributions of this study are identifying effective and ineffective illusion combinations for enhancing the KINVIS and demonstrating that a simple device can achieve these illusions. These findings mark the first step toward a more accessible KINVIS.