Dunbar Number

生物学家Dunbar在1992年提出了一个名为Dunbar Number的理论:灵长类动物的大脑容量与它的族群大小有关,然后推论出一些人类大脑能够维持的关系数量,例如typical person would have:

5 intimate friends
15 trusted friends
35 close friends
150 casual friends

Dunbar’s Number:

A measurement of the “cognitive limit to the number of individuals with whom
    any one person can maintain stable relationships.