The Dunbar Number is a cognitive limit first proposed by British anthropologist Robin Dunbar in 1992. It states that the maximum number of social relationships that the brain can actively maintain is roughly 150, which is hypothesized to be the result of the size of the neocortex. This number has been used to explain the size of human hunter-gatherer societies, a common limit of associates observed in many primates, as well as how social media networks are curated and maintained.

See also: evolutionary psychology, edge of chaos, cultural evolution