Cognitive limits cap stable social relationships at roughly 150, with tighter layers of about 5, 15, and 50.
The layers are the robust finding: about 5 intimates, 15 close friends, 50 friends, 150 acquaintances, each roughly tripling. The specific number and the neocortex explanation are both contested.
In practice
- A department of 40 knows everyone; at 200 the same organisation invents a directory, an org chart and an all-hands, because nobody can hold it any more.
- A community group that ran on a WhatsApp thread for years needs a committee and minutes once it passes about 150 members.
- Possible explanations
- One explanation Dunbar offered is cognitive: tracking who stands in what relation to whom costs attention that grows with group size. Another is time, since relationships need maintenance and the hours available cap how many can be kept warm.
- In its favour
- The layered structure appears in several independent datasets, including personal networks, Christmas card lists and the sizes of military units.
- Against it
- A 2021 reanalysis of the primate data found the estimate so imprecise as to be consistent with anything from a few dozen to several hundred, and the neocortex argument it rests on is disputed.
- Standing
- Layer sizes vary by method and the neocortex argument is contested.
- Further reading
- Wikipedia
- Subject
- Networks & Collective Behavior
- Essay
- How connections shape what crowds do