Designing and Assessing Expressive Open-Source Faces for the Baxter Robot.

Facial expressions of both humans and robots are known to communicate important social cues to human observers. Nevertheless, faces for use on the flat panel display screens of physical multi-degree-of-freedom robots have not been exhaustively studied. While surveying owners of the Rethink Robotics Baxter Research Robot to establish their interest, we designed a set of 49 Baxter faces, including seven colors (red, orange, yellow, green, blue, purple, and gray) and seven expressions (afraid, angry, disgusted, happy, neutral, sad, and surprised). Online study participants (N = 568) drawn equally from two countries (US and India) then rated photographs of a physical Baxter robot displaying randomized subsets of the faces. Face color, facial expression, and onlooker country of origin all significantly affected the perceived pleasantness and energeticness of the robot, as well as the onlooker's feelings of safety and pleasedness, with facial expression causing the largest effects. The designed faces are available to researchers online.