Dunbar's number is a suggested cognitive limit to the number of people with whom one can maintain stable social relationships. This number was first proposed by British anthropologist Robin Dunbar, who found a correlation between primate brain size and average social group size. By using the average human brain size and extrapolating from the results of primates, he proposed that humans can only comfortably maintain 150 stable relationships. The book on Amazon.
How Many Friends Does One Person Need?: Dunbar's Number and Other Evolutionary Quirks: Amazon.co.uk: Professor Robin Dunbar: Books
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