Dunbar’s Number: Why 150 People Fit In Our Social Brain

In this episode Dr. Shepard explores Dunbar’s Number, the idea that humans can meaningfully maintain about 150 social relationships. Drawing from Robin Dunbar’s book "How Many Friends Does One Person Need?," Dr. Shepard explains the social intelligence hypothesis that links neocortex size to social-group limits, breaks down the layered structure of relationships (from 3–5 closest friends to 1,500 recognizable faces), and describes how frequency and intimacy shape each circle.

The episode also examines how gossip expands social knowledge, how social media and smartphones change our sense of community and parasocial ties, and the friendship formula (investment, emotional closeness, trust, support) for building deep connections. Dr. Shepard shares personal anecdotes about community, presence, and how phones affect conversation depth, and offers practical advice on moving online acquaintances offline to develop real friendships. He ends with reflections on choosing where to invest your time and the unique, uncodified nature of friendship.