Modeling the Timing and Duration of Grip Behavior to Express Emotions for a Social Robot

This letter addresses the effects of grip timing to express a robot's emotions to people while they are watching a video stimulus together. Past studies on human-robot touch interaction focused on the types of touch behaviors for expressing a robot's emotion, but timing factors have received less attention. In this letter, we conducted data collection to investigate the appropriate grip timing to express heartwarming and horror emotions. Participants identified touch (grip) timing and durations by using a robot while they are watching video stimuli. Typically, they preferred a grip timing before a climax for horror videos but after a climax for heartwarming videos. We modeled the timing and durations by a fitting approach to probabilistic distribution to reproduce human-like touch behaviors, and also we implemented the models to an android robot.