1. Introduction
Over 14 million home robots (e.g., Roomba vacuum cleaners) were made and distributed by the iRobot company since 2002 [1]. Just last year, 1000 humanoid Pepper robots were made and distributed in Japan [2]. In the upcoming years, it is expected that humans will view and interact with more robots of various types - and not just in one-on-one interactions, but in interactions involving groups of humans and groups of robots.