On-time measurement of subjective anxiety of a passenger in an autonomous vehicle: Gradually changing sounds decreases anxiety of passenger

Abstract

The current study examined the possibility of measuring the subjective anxiety in real-time by means of a novel handle-shaped device, caused by riding an autonomous car. In our experiment, a participant was shown computer graphics (CG) animation, which gave the person a virtual experience of riding a new autonomous car. The CG animation stimuli were made with three variables: maximum speed (19 km/h, 160 km/h, or 320 km/h), acceleration/deceleration pattern (linear or exponential), and with and without ascending/descending sounds (sound, or no sound). The participants grasped the handle and moved it in the longitudinal direction, i.e., pulling when they experienced anxiety and pushing when they felt relaxed. Results of experiments by 16 participants showed that they moved the handle depending on the stimulus of speed at that instant, which indicated that our handle-shaped device was useful in assessing the participants’ anxiety on time. In addition, results indicated that sounds, especially those which gradually ascending with acceleration, could diminish the subjective anxiety under some conditions.