Phantom sensation: threshold and quality indicators of a tactile illusion of motion

Abstract

Utilizing a randomized, blind, controlled experiment, and the ascending method of limits, we determined the minimum amplitude of motion at which individuals perceive a tactile illusion called moving phantom sensation, the perceived level of clarity and continuity of motion. Implementing tactile illusions in virtual/augmented reality, sensory substitution systems, and other human–computer interaction technologies results in interfaces with improved resolution, using two vibrating actuators only. The actuators are attached to the skin in different locations to render a moving phantom sensation. The intensity of vibrations increases in one actuator while decreases in the other according to the envelope of the voltage supply signals. This intensity variation creates the illusion of a vibrating point moving between the actuators. We gradually increased the amplitude of motion until the participant reported perceiving the illusion, for eight values of duration of the stimulus from 0.1 to 6.0 s. Participants perceived the illusion at a minimum amplitude of motion of 20%; being 100% the motion from one actuator to the other. The median level of clarity of the perceived illusion at the minimum amplitude of motion was 2 (not so clear). Finally, we found a positive correlation between duration and continuity of motion.