Social group membership

tipping-pointNew York author, Malcolm Gladwell discusses the Dunbar number in his popular 2000 book The Tipping Point. Gladwell describes the company W. L. Gore and Associates, now known for the Gore-Tex brand. By trial and error, the leadership in the company discovered that if more than 150 employees were working together in one building, different social problems could occur.

The company started building company buildings with a limit of 150 employees and only 150 parking spaces. When the parking spaces were filled, the company would build another 150-employee building. Onwards it goes. Sometimes these buildings would be placed only short distances apart. The company is also known for the open allocation company structure.

148 is the magical number called ‘Dunbar’s Number,’ oftentimes rounded up to 150. It is attributed to British evolutionary anthropologist Robin Dunbar, who has stated that 150 people is the ‘point beyond which members of any social group lose their ability to function effectively in social relationships.’

In Dunbar’s research, he mentioned that the 150 people are made up of:

  • 5 intimate friends
  • 15 good friends (including the 5 intimate friends)
  • 50 friends (including the 5 intimate friends and 15 good friends)
  • 150 acquaintances (all-encompassing)

Dunbar mentions two main numbers: an inner core of about 5 people to whom we devote about 40 percent of our available social time and 10 more people to whom we devote another 20 percent. All in all, we devote about two-thirds of our time to just 15 people, and 40% with the remaining 135 people. The number can be said to derive from our brain’s ability to maintain memories of 150 people, as well as the time necessary to devote to the group in order to keep relationships going.

What examples of this are there in history?

  • Neolithic farming communities are known to be around 150 people before it splits into a separate community
  • Roman military armies are approximately 150 soldiers in size; other modern armies are known to be typically 120–180
  • Average parish size for the Hutterites and Amish, denominations known for espousing communal living
  • Jury sizes are usually 12 people large
  • Coming back to Gore Tex, the work environment of 150 people results in everyone knowing each other’s name, no line-management systems or name badges, and everyone is committed to each other and the communal vision. It acts more like a lattice rather than a tree organisational structure, to quote Christopher Alexander.

Renowned evolutionary anthropologist Professor Robin Dunbar visits the RSA (Royal Society for the encouragement of Arts, Manufactures and Commerce) to explain how the very distant past underpins all of our current behaviours, and how we can best utilise that knowledge.

Robin Dunbar Anthropologist, evolutionary psychologist Robin, currently director of the Institute of Cognitive and Evolutionary Anthropology of the University of Oxford, is renowned for creating a formula which is now known as ‘Dunbar’s number’ – and that number is 150. This calculates the ‘cognitive limit’ of the number of people we can hold meaningful friendships with. When it was first formulated it created a fevered debate about the nature of and the differences between, online and real ‘friendships’. Robin will explore the psychology and ethology of romantic love to find out if the brain – and science – can help us explain how and why we fall in love.

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