Dunbar's Number

Dunbar's number is a proposed approximate social-group size associated with the social-brain hypothesis, often summarized as around 150 relationships. It is not an established universal ceiling. The extrapolation from primate brain and group-size data is disputed, and relationship types and contexts differ.

Dunbar's proposed number connects social-group size with a hypothesis about cognitive demands. The widely repeated value near 150 should not be treated as a meter reading for every person or an organizational deadline. Reanalysis of the primate-data extrapolation found estimates too uncertain to establish one universal human limit.

The useful practical question is which relationships require what kind of attention and coordination. A broad network of occasional contacts differs from a small group making difficult joint decisions. Examine communication demands, actual missed connections, and participants' preferences. Add structure when it solves an observed problem, not because the member count has crossed a supposedly biological threshold.

When to use it

When investigating social coordination demands, distinguishing close relationships from occasional contacts, or evaluating whether a proposed group-size rule is supported.

How it can help

Examine the actual attention and coordination demands of relationships and groups. Use smaller working units or clearer structures when they solve observed problems, rather than applying a fixed headcount rule.