Subthalamic nucleus detects unnatural android movement

Abstract

An android, i.e., a realistic humanoid robot with human-like capabilities, may induce an uncanny feeling in human observers. The uncanny feeling about an android has two main causes: its appearance and movement. The uncanny feeling about an android increases when its appearance is almost human-like but its movement is not fully natural or comparable to human movement. Even if an android has human-like flexible joints, its slightly jerky movements cause a human observer to detect subtle unnaturalness in them. However, the neural mechanism underlying the detection of unnatural movements remains unclear. We conducted an fMRI experiment to compare the observation of an android and the observation of a human on which the android is modelled, and we found differences in the activation pattern of the brain regions that are responsible for the production of smooth and natural movement. More specifically, we found that the visual observation of the android, compared with that of the human model, caused greater activation in the subthalamic nucleus (STN). When the android’s slightly jerky movements are visually observed, the STN detects their subtle unnaturalness. This finding suggests that the detection of unnatural movements is attributed to an error signal resulting from a mismatch between a visual input and an internal model for smooth movement.

Effectiveness of Multimedia Pedagogical Agents Predicted by Diverse Theories: a Meta-Analysis

“…We predicted that an agent exhibiting simple dynamic facial expressions (e.g., unnatural lip sync) would evoke more eeriness and less learning outcomes than total static facial expressions or totally human and complex dynamic facial expressions. In this line, previous research with multimedia agents has shown these detrimental outcomes when the agents approach but fail to imitate the social naturality of humans (e.g., Ikeda et al 2017;Tinwell et al 2011;Veletsianos 2012).…”