9.3. Embodied Communication 163

9.3. Embodied Communication 163 9.3 Embodied Communication Next we turn to the potential cognitive implications of seeking to achieve goals in an environ- ment in which multimodal communication with other agents plays a prominent role. Consider a community of embodied agents living in a shared world, and suppose that the agents can communicate with each other via a set of mechanisms including: e Linguistic communication, in a language whose semantics is largely (not necessarily wholly) interpretable based on the mutually experienced world e Indicative communication, in which e.g. one agent points to some part of the world or delimits some interval of time, and another agent is able to interpret the meaning e Demonstrative communication, in which an agent carries out a set of actions in the world, and the other agent is able to imitate these actions, or instruct another agent as to how to imitate these actions e Depictive communication, in which an agent creates some sort of (visual, auditory, etc.) construction to show another agent, with a goal of causing the other agent to experience phenomena similar to what they would experience upon experiencing some particular entity in the shared environment e Intentional communication, in which an agent explicitly communicates to another agent what its goal is in a certain situation ! It is clear that ordinary everyday communication between humans possesses all these aspects. We define the Embodied Communication Prior (ECP) as the probability distribution in which the probability of an entity (e.g. a goal or environment) is proportional to the difficulty of describing that entity, for a typical member of the community in question, using a particular set of communication mechanisms including the above five modes. We will sometimes refer to the prior probability of an entity under this distribution, as its “simplicity” under the distribution. Next, to further specialize the Embodied Communication Prior, we will assume that for each of these modes of communication, there are some aspects of the world that are much more easily communicable using that mode than the other modes. For instance, in the human everyday world: e Abstract (declarative) statements spanning large classes of situations are generally much easier to communicate linguistically e Complex, multi-part procedures are much easier to communicate either demonstratively, or using a combination of demonstration with other modes e Sensory or episodic data is often much easier to communicate demonstratively e The current value of attending to some portion of the shared environment is often much easier to communicate indicatively e Information about what goals to follow in a certain situation is often much easier to com- municate intentionally, i.e. via explicitly indicating what one’s own goal is These simple observations have significant implications for the nature of the Embodied Com- munication Prior. For one thing they let us define multiple forms of knowledge: e Isolatedly declarative knowledge is that which is much more easily communicable lin- guistically 1 in Appendix ?? we recount some interesting recent results showing that mirror neurons fire in response to some cases of intentional communication as thus defined HOUSE_OVERSIGHT_013079