Expressive path shape (swagger): Simple features that illustrate a robot's attitude toward its goal in real time

Expressive motion can situate a robot's attitude in its task motions, illustrating real-time reactions. Inspired by acting movement training, we construct path shape features that layer expression into a mobile robot's motion traversal. Our video-study results show that simple variations of path shape and orientation can influence human perceptions of a robot's task, focus, and confidence. We further find that sequencing path features is a useful way to create expressions that are pinpointed in time without requiring changes in velocity. Our quantitative features represent the Laban Space Effort: using path shape and orientation along the path to communicate the direct or indirect attitude of the robot toward its target destination (acting vocabulary italicized). These features illustrate expressive or stylistic aspects of the robot's inner state, filling a gap in the pre-existing literature that has mostly focused on task legibility. Our future work will evaluate temporal and spatial robot motion features in explicit interaction contexts.