The Exploration of the Uncanny Valley from the Viewpoint of the Robot\u2019s Nonverbal Behaviour

Abstract

Many studies have been conducted to find approaches to overcome the Uncanny Valley. However, the focus on the influence of the robot’s appearance leaves a big missing part: the influence of the robot’s nonverbal behaviour. This impedes the complete exploration of the Uncanny Valley. In this study, we explored the Uncanny Valley from the viewpoint of the robot’s nonverbal behaviour in regard to the Uncanny Valley hypothesis. We observed a relationship between the participants’ ratings on human-likeness of the robot’s nonverbal behavior and affinity toward the robot’s nonverbal behavior, and define the point where the affinity toward the robot’s nonverbal behavior significantly drops down as the Uncanny Valley. In this study, an experiment of human–robot interaction was conducted. The participants were asked to interact with a robot with different nonverbal behaviours, ranging from 0 (no nonverbal behavior, speaking only) to 3 (gaze, head nodding, and gestures) combinations and to rate the perceived human-likeness and affinity toward the robot’s nonverbal behavior by using a questionnaire. Additionally, the participants’ fixation duration was measured during the experiment. The result showed a biphasic relationship between human-likeness and affinity rating results. A curve resembling the Uncanny Valley is found. The result was also supported by participants’ fixation duration. It showed that the participants had the longest fixation at the robot when the robot expressed the nonverbal behaviours that fall into the Uncanny Valley. This exploratory study provides evidence suggesting the existence of the Uncanny Valley from the viewpoint of the robot’s nonverbal behaviour.