As humans we are fundamentally social creatures. For most people an ordinary day is filled with social interaction. We converse with our family and friends. We talk with our co-workers as we carry out our work. We engage in routine exchanges with familiar strangers at the bus stop and in the grocery store. This social interaction is not just talk: we make eye contact, nod our heads, wave our hands, and adjust our positions. Not only are we busy interacting, we are also remarkably sensitive to the behaviors of those around us. Our world is filled with social cues that provide grist for inferences, planning and action. We grow curious about a crowd that has gathered down the street. We decide not to stop at the store because the parking lot is jammed. We join in a standing ovation even though we didn’t enjoy the performance that much. Social interactions like these contribute to the meaning, interest and richness of our daily life.