Vibrational Artificial Subtle Expressions: Conveying System’s Confidence Level to Users by Means of Smartphone Vibration

Artificial subtle expressions (ASEs) are machine-like expressions used to convey a system's confidence level to users intuitively. So far, auditory ASEs using beep sounds, visual ASEs using LEDs, and motion ASEs using robot movements have been implemented and shown to be effective. In this paper, we propose a novel type of ASE that uses vibration (vibrational ASEs). We implemented the vibrational ASEs on a smartphone and conducted experiments to confirm whether they can convey a system’s confidence level to users in the same way as the other types of ASEs. The results clearly showed that vibrational ASEs were able to accurately and intuitively convey the designed confidence level to participants, demonstrating that ASEs can be applied in a variety of applications in real environments.