Wednesday, July 15, 2009

Dunbar's Number and Security

Post by Bruce Schneier on his blog, "Security, Group Size, and the Human Brain"

In a 1992 article, Dunbar used the correlation observed for non-human primates to predict a social group size for humans. Using a regression equation on data for 38 primate genera, Dunbar predicted a human "mean group size" of 148 (casually rounded to 150), a result he considered exploratory due to the large error measure (a 95% confidence interval of 100 to 230).

Several layers of natural human group size
3-5: Clique - people you would turn to in times of severe emotional distress
12-20: Sympathy group - people with whom you have special ties
30-50: Typical size of hunter-gatherer overnight camps
150: Approximate maximum number of co-workers
500: Megaband
1500: Tribe

Note: All of these numbers have very large confidence intervals.

These numbers (and particularly the ~150 number) are important because of their effects on organizational behavior.

Coherence can become a real problem once organizations get above about 150 in size. So as group sizes grow across these boundaries, they have more externally imposed infrastructure -- and more formalized security systems.

Small companies can get by without the internal forms, memos, and procedures that large companies require; when does what tend to appear?

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