British anthropologist Robin Dunbar has proposed that humans can only maintain around 150 meaningful relationships at any one time, a figure known as Dunbar's number. This limit, derived from studies of primate brain size and social behaviour, appears consistent across historical and modern groups, from hunter-gatherer societies to military organisations and even Christmas card lists.
Dunbar's research suggests that the neocortex—the brain region linked to cognition and language—limits the complexity of social networks. Beyond 150, groups tend to split or lose cohesion. However, the number is not fixed; it represents a range, with extroverts often having larger, thinner networks and introverts smaller, closer ones.
Within the 150, nested layers exist: about 5 loved ones, 15 good friends, 50 friends, 500 acquaintances, and 1,500 recognisable faces. These layers are shaped by how often people interact face-to-face, as time for socialising is limited. Women tend to have slightly more close contacts than men.
Some organisations, like the Swedish Tax Authority, have restructured offices to stay within the 150-person threshold. While not all researchers agree on the exact number, the concept remains a useful tool for understanding social limits in an era of digital networks with thousands of followers.
