Evaluations of involuntary cross-modal expressions on the skin of a communication robot

In this paper, we introduce a unique combination of multiple involuntary expressions on the skin of a robot; namely, goose bumps, sweats, and shivers, which represent instinctive fears of the anthropomorphic presence. Humans and other living beings express not only voluntary but also involuntary modalities, including physiologic reactions. We expected these fake-involuntary expressions of a robot to realize the life-like or human-alike presence of the robot. In this research, we focused on the unique expression of a strong fear represented not only by the facial expressions but also by the combination of involuntary goose bumps, sweats, and shivers, and so on. Our proposed method utilizes multiple thin rods under the robot's skin to generate the goose bumps. A vibration motor and a water tank with a balloon are also attached to the system to create combined expressions. The results of the evaluation showed the effectiveness of the combination of three different involuntary expressions and the different nuances of the expression through a variety of unique combinations.