Part II — Actions performed in the context of a joint activity comprise two aspects: functional and communicative. The functional component achieves the goal of the action, whereas its communicative component, when present, expresses some information to the actor’s partners in the joint activity. The interpretation of such communication requires leveraging information that is public to all participants, known as common ground. Humans cannot help but infer some meaning – whether or not it was intended by the actor – and so robots must be cognizant of how their actions will be interpreted in context. In this talk, I address the questions of why and how robots can deliberately utilize this communicative channel on top of normal functional actions to work more effectively with human partners. We examine various human-robot interaction domains, including social navigation and collaborative assembly.