Hey Robot, Which Way Are You Going? Nonverbal Motion Legibility Cues for Human-Robot Spatial Interaction

TL;DR

This study investigates nonverbal motion cues for mobile robots to improve pedestrian understanding and acceptance, comparing projected arrows and flashing lights in various scenarios through an online user study.

Contribution

It introduces and evaluates nonverbal motion legibility cues, demonstrating that projected arrows are more socially acceptable than flashing lights for communicating robot intentions.

Findings

Projected arrows increased social acceptability over flashing lights.

Absence of cues was socially unacceptable.

Motion cues improved pedestrian understanding and acceptance.

Abstract

Mobile robots have recently been deployed in public spaces such as shopping malls, airports, and urban sidewalks. Most of these robots are designed with human-aware motion planning capabilities but are not designed to communicate with pedestrians. Pedestrians that encounter these robots without prior understanding of the robots' behaviour can experience discomfort, confusion, and delayed social acceptance. In this work we designed and evaluated nonverbal robot motion legibility cues, which communicate a mobile robot's motion intention to pedestrians. We compared a motion legibility cue using Projected Arrows to one using Flashing Lights. We designed the cues to communicate path information, goal information, or both, and explored different Robot Movement Scenarios. We conducted an online user study with 229 participants using videos of the motion legibility cues. Our results show that the absence of cues was not socially acceptable, and that Projected Arrows were the more socially acceptable cue in most experimental conditions. We conclude that the presence and choice of motion legibility cues can positively influence robots' acceptance and successful deployment in public spaces.