Quantifying the Sense of Control through the Hand Blink Reflex in Human-Robot Interaction

Humans and robots are expected to collaborate closely sharing the same working environment. However, a quantitative measure of the perceived sense of control (SoC) in interacting with artificial systems is still an unmet need. This work introduces a ground-breaking approach that will profoundly impact the way of evaluating the SoC in human-robot interaction. We investigated the human behaviour during human-robot interactions by examining the Hand Blink Reflex (HBR). The HBR is an innate defensive reflex elicited by the electrical stimulation of the median nerve and can be measured using EMG recordings from the orbicularis oculi muscles. We recorded HBR in twenty subjects during different experimental conditions considering a robotic arm entering the defensive peripersonal space (DPPS) at near or far proximities to the face and under different control modalities: autonomous robot movement, human control limited to starting or stopping the robot, and human fully controlling the speed of the robot. According to predictions, the HBR amplitude is modulated by the proximity of the robotic arm to the DPPS. Crucially, the more the human confidence in the robot control, the lower the HBR amplitude. This novel method quantifies human confidence in robot control, potentially advancing human-robot collaboration by enhancing our understanding of the neural mechanisms underlying perceived control and safety in shared workspaces. Results can be further exploited for comparing the effectiveness of robot control interfaces and algorithms.