  Despite the rise of mobile robot deployments in home and work settings,
perceived safety of users and bystanders is understudied in the human-robot
interaction (HRI) literature. To address this, we present a study designed to
identify elements of a human-robot encounter that correlate with observed
stress response. Stress is a key component of perceived safety and is strongly
associated with human physiological response. In this study a Boston Dynamics
Spot and a Unitree Go1 navigate autonomously through a shared environment
occupied by human participants wearing multimodal physiological sensors to
track their electrocardiography (ECG) and electrodermal activity (EDA). The
encounters are varied through several trials and participants self-rate their
stress levels after each encounter. The study resulted in a multidimensional
dataset archiving various objective and subjective aspects of a human-robot
encounter, containing insights for understanding perceived safety in such
encounters. To this end, acute stress responses were decoded from the human
participants' ECG and EDA and compared across different human-robot encounter
conditions. Statistical analysis of data indicate that on average (1)
participants feel more stress during encounters compared to baselines, (2)
participants feel more stress encountering multiple robots compared to a single
robot and (3) participants stress increases during navigation behavior compared
with search behavior.
