A growing body of literature on humans and animals documents the link between social integration and affiliative relationships and a variety of health and disease outcomes, including mortality. The actual mechanisms through which these efforts occur are, however, not well understood. Emotion probably plays a central role in mediating connections between relational experiences, underlying neurobiological processes, and health outcomes. Many prior studies have focused on the size and proximity of social networks, thereby neglecting their emotional features. When studied, emotion in social...