Analysis of Pleasantness Evoked by Various Airborne Ultrasound Tactile Stimuli Using Pairwise Comparisons and the Bradley-Terry Model

The presentation of a moving tactile stimulus to a person's forearm evokes a pleasant sensation. The speed, intensity, and contact area of the strokes should be systematically changed to evaluate the relationship between pleasantness and tactile stimuli in more detail. Studies have examined the relationship between stroking stimulation and pleasant sensations using airborne ultrasound tactile displays. The ultrasound-based method has the advantage of reproducible control of the speed, intensity, and contact area of the stimulus. In this study, we prepared new stimuli focusing on the modulation methods and the contact area and aimed to clarify their relationship with pleasantness in more detail. Evaluating subjective sensations, such as pleasantness, numerically and consistently is challenging, warranting evaluation based on comparison. We propose a stimulus evaluation method that combines rough evaluation using Likert scales, detailed evaluation using pairwise comparisons, and quantification of comparison data using the Bradley--Terry model. As a result, we confirmed that the stimulus using lateral modulation and that with a large contact area used in this study were more pleasant than the conventional stimulus for six out of ten participants.