Dunbars Magic Number – stop at 150 people in a group!
I have been reading "The Tipping Point" by Malcolm Gladwell lately... highly recommended! One of the ideas that got me interested was Gladwells mentioning of the magic number 150.
Robin Dunbar discovered that 150 was the maximum number of people in an effective group. He did it by researching the way the size of the Neo-Cortex in the brain of mammals correlates with their preferred size of group. From the size of the human Neo-Cortex he could deduce the number to be somewhere around 150. Then, as an anthropologist, he went out and found out, that this number was the same as the size of the typical settlements in primitive tribes. It was also the maximum number of personel in military units.
Beyond 150 we begin to loose the ability to have full relationships with other people. We begin to think of them in 2D. We don't know what their interests are, what they excel at. We simply don't care about them anymore.
The consequense of this is, that groups above 150 are unstable compared to sub-150 groups. These groups need more control and structure, and formalized knowledge-sharing, than sub-150 groups. Before you hit the magic number you can rely on personal trust and relationsships to solve the groups problems. Beyond this the group starts to split up into smaller clans, with their own agendas.
It is really interesting how this maximum group-size has been adopted in the way Gore International (Gore-Tex) organize the corporate culture. Every time a division grows beyond 150 it gets split up. And because of this approach they succeed in having a much simpler leadership structure, and highly cross-functional teams.
Further Reading:
- Inside the Monkeysphere - A funny rant about the implications of the number 150.
- Wikipedia Entry on Dunbars Number
- Jens Poder
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