Dunbar’s Number — Explained
Dunbar’s Number refers to the cognitive limit on the number of stable, meaningful social relationships a person can maintain — typically around 150.
Proposed by anthropologist Robin Dunbar in the early 1990s, it’s based on research linking neocortex size to social group size in primates, then extrapolated to humans.
The key idea: our brains can only manage a limited number of people whose relationships with us (and with each other) we can track in any depth.
Dunbar’s Social Layers
Dunbar found that human relationships form nested circles of intimacy, each layer roughly three times larger than the one before it — but with decreasing emotional closeness and interaction frequency.
LayerApprox. SizeRelationship TypeTypical Frequency of Contact / Emotional Closeness1st Circle****5Closest friends & family — your “support clique”Daily or near-daily contact; deepest emotional ties2nd Circle****15Good friends you confide in and rely onWeekly contact; high emotional closeness3rd Circle****50Friends you might invite to a big personal event (e.g. wedding)Monthly contact; moderate closeness4th Circle****150Meaningful relationships — people you know personally and would help if neededA few times per year; recognize and understand social context5th Circle****500Acquaintances — people whose names and faces you recognizeOccasional interaction or recognition6th Circle****1,500People you can place a name to (the limit of facial recognition memory)Rare interaction; mostly recognition only
Modern & Practical Implications
Even in the digital era:
- People still maintain about 100–200 active online relationships despite thousands of “followers.”
- Teams, villages, and companies often stabilize near this size before naturally splitting or losing cohesion.
- Some organizations (like W. L. Gore, maker of Gore-Tex) deliberately limit unit size to ~150 to preserve strong internal culture and trust.
