Full Idea
Brain size in primates is closely associated with the size of the social group in which the animal lives.
Gist of Idea
In primates, brain size correlates closely with size of social group
Source
Rita Carter (Mapping the Mind [1998], p.257)
Book Reference
Carter,Rita: 'Mapping the Mind' [Phoenix 2000], p.257
A Reaction
Intriguing. Humans can have huge social groups because of language, which suggests a chicken-or-egg question. Language, intelligence and size of social group must have expanded together in humans.