Dunbar's Number: The Limit of Relationships
How many friends can your brain actually manage at once?
Dunbar's number is a cognitive limit to the number of stable social relationships a person can maintain at one time. Proposed in the 1990s by British anthropologist Robin Dunbar, who studied the correlation between primate brain size and social group sizes, the number is approximately 150 for humans. Maintaining a relationship requires cognitive effort; you must remember who the person is, your history together, how they feel, and how they relate to others in your network. When a group exceeds 150 people, it becomes too difficult for the brain to keep track through personal contact alone. At that point, formal rules, laws, and hierarchies are needed to keep the group functioning without chaos. This limit applies to relationships where you know the person well enough that you would feel comfortable joining them if you met at a cafe.
Think of your social media. You might have 1,000 followers, but if you filter the list to people you actually care about, talk to, and know what they are up to, you will likely land close to 150.
It explains why stone-age villages, Roman military units, and successful modern companies often split their organizations into smaller units as soon as they exceed 150 people.
A common misconception is that we can only know 150 people in total. In reality, we can recognize thousands of faces and names, but 150 is the limit for genuinely mutual relationships.
Go through your phone's call log and count how many people you have had personal contact with in the past six months.
Dunbar's number shows that the human brain has a natural limit of around 150 stable relationships.
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