Eikonal Blog


Dunbar’s numbers

Dunbar numbers for current variant/species of humans:

  • 7 – immediate family
  • 21 – extended family and close friends
  • 35 – community, friend, distant family
  • 60+ – everyone else
  • 150 – the maximal # of people one may know by name (really?)


  • “Human Brain Limits Twitter Friends to 150” (The Physics arXiv Blog; 2011.05.30) – http://www.technologyreview.com/blog/arxiv/26824/The number of people we can truly be friends with is constant, regardless of social networking services like Twitter, according to a new study of the network.
    • “Validation of Dunbar’s number in Twitter conversations” by Bruno Goncalves, Nicola Perra and Alessandro Vespignani (arXiv.org > physics > arXiv:1105.5170 [physics.soc-ph]; 2011.05.28) – http://arxiv.org/abs/1105.5170
    • Abstract: Modern society’s increasing dependency on online tools for both work and recreation opens up unique opportunities for the study of social interactions. A large survey of online exchanges or conversations on Twitter, collected across six months involving 1.7 million individuals is presented here. We test the theoretical cognitive limit on the number of stable social relationships known as Dunbar’s number. We find that users can entertain a maximum of 100-200 stable relationships in support for Dunbar’s prediction. The “economy of attention” is limited in the online world by cognitive and biological constraints as predicted by Dunbar’s theory. Inspired by this empirical evidence we propose a simple dynamical mechanism, based on finite priority queuing and time resources, that reproduces the observed social behavior.
  • Dunbar’s number (WikiPedia) – http://en.wikipedia.org/wiki/Dunbar%27s_number
  • “OMG: brains can’t handle all our Facebook friends” by Chris Gourlay (The Sunday Times; 2010.01.24) – http://technology.timesonline.co.uk/tol/news/tech_and_web/the_web/article6999879.ece
    • … “Dunbar developed a theory known as “Dunbar’s number” in the 1990s which claimed that the size of our neocortex — the part of the brain used for conscious thought and language — limits us to managing social circles of around 150 friends, no matter how sociable we are.”
  • Dunbar’s number – (Justified by the Scriptures; 2010.11.04) – http://justifiedbythescriptures.wordpress.com/2010/11/04/dunbars-number/
  • “Social Media and Me – It’s Good to Talk” (Vintage1951 blog; 2010.07.07) – http://vintage1951.wordpress.com/2010/07/07/social-media-and-me-its-good-to-talk-2/
    • “Dunbar’s Number is a well-known concept in anthropology, which states that an individual can only maintain strong stable relationships with around 150 people. The number is held to be a function of the size of the neocortex, a theory tested by comparing the social groupings of other primates. Some people claim that any group loses cohesion and eventually its identity when its size exceeds Dunbar’s number.
  • “The Tipping Point – Malcolm Gladwell – Review” by Phil O’Brien (Personal Network Blog; 2010.07.22) – http://personalnetwork.wordpress.com/2010/07/22/the-tipping-point-malcolm-gladwell-review/
    • “Dunbar’s Number. He explains the principle of humans naturally having a most efficient group size of 150 people. Robin Dunbar (from Oxford University) has done research in to ancient civilisations – and modern business groups … and 150 keeps on recurring.”
  • “150 Connections on LinkedIn – should I retire on Dunbar’s Number?” by Phil O’Brien (Personal Network Blog; 2010.09.10) – http://personalnetwork.wordpress.com/2010/09/03/150-connections-on-linkedin-should-i-retire-on-dunbars-number/
  • “Dunbar’s Number – is it 22,500 in practice?” by Phil O’Brien (Personal Network Blog; 2010.11.01) – http://personalnetwork.wordpress.com/2010/11/01/dunbars-number-is-it-22500-in-practice/
  • “Sorry, Facebook friends: Our brains can’t keep up” by Don Reisinger (Digital Home; 2010.02.28) – http://news.cnet.com/8301-13506_3-10440330-17.html
  • “How Many Friends Are Too Many?” (Healthymemory’s Blog) – http://healthymemory.wordpress.com/2010/11/07/how-many-friends-are-too-many/
  • “Unravelling the size distribution of social groups with information theory on complex networks” by A. Hernando, D. Villuendas, C. Vesperinas, M. Abad, A. Plastino (arXiv; v3 = 2009.09.16) – http://arxiv.org/abs/0905.3704v3
  • “Defying the Dunbar number” by Rajiv Jayaraman (MIS Asia; 2009.02.20) – http://mis-asia.com/opinion__and__blogs/bloggers/defying-the-dunbar-number
    • “There is a need to double the Dunbar number to at least 300 to reflect the realities of the new hyper-connected Web 2.0 world. Will you dig that?
  • “Defying the Dunbar number” (Knolskape; 2009.02.20) – http://www.knolskape.com/blog/2009/02/defying-the-dunbar-number/
  • “Primates on Facebook – Even online, the neocortex is the limit” (the exonomist; 2009.02.26) – http://www.economist.com/node/13176775?story_id=13176775
  • “What is the Monkeysphere?” by David Wong (Cracked.com; 2007.09.30) – http://www.cracked.com/article_14990_what-monkeysphere.html
    • “You see, monkey experts performed a monkey study a while back, and discovered that the size of the monkey’s monkey brain determined the size of the monkey groups the monkeys formed. The bigger the brain, the bigger the little societies they built.They cut up so many monkey brains, in fact, that they found they could actually take a brain they had never seen before and from it they could accurately predict what size tribes that species of creature formed.

      Most monkeys operate in troupes of 50 or so. But somebody slipped them a slightly larger brain and they estimated the ideal group or society for this particular animal was about 150.

      That brain, of course, was human. Probably from a homeless man they snatched off the streets.”
  • “The ultimate brain teaser” – http://www.liv.ac.uk/researchintelligence/issue17/brainteaser.html
  • “The Dunbar Number” by Jeff Freeman (2004?.06.28) – http://web.archive.org/web/20051214141613/http://mythical.blogspot.com/2004_06_01_mythical_archive.html
  • “Dunbar, Altruistic Punishment, and Meta-Moderation” by Christopher Allen (Life Without Alacrity; 2005.03.17) – http://www.lifewithalacrity.com/2005/03/dunbar_altruist.html
    • “There I was able to show that even though the Dunbar Number might predict a mean group size of 150 for humans, that in fact for non-survival oriented groups the mean was significantly less, probably between 60 to 90.”
  • “The Dunbar Number as a Limit to Group Sizes” by Christopher Allen (Life Without Alacrity; 2004.03.10) – http://www.lifewithalacrity.com/2004/03/the_dunbar_numb.html
  • “Communities of practice and Dunbar’s number” (Mopsos; 2004.03.12) – http://www.blog.mopsos.com/archives/000075.html
    • “Essentially, as we increase group sizes beyond 80, to 150, 200, or even 350-500, we typically do so by breaking larger groups down into smaller ones, and continually reducing community sizes down to the point where they can be understood and managed by people — and so efficiency reasserts itself.In my experience and vision of communities of practice, I tend to find similar numbers floating around. Typically vibrant communities of practice have around 100 – 150 members. As social structures, they are “onion-shaped”, with layers of membership behaviors.

      At the center, the “core group” of the community of practice is typically composed of 5 to 7 people. These are the guys who are willing to spend some time together, typically 15%-20% of their time (not much more, because they are busy on their projects anyway), reflecting on past experience and planning ahead for the community’s learning activities in a peer mode. Then you have a second layer of 20-30 active contributors, typically those who follow the community ritual: they come regularly at meetings, they often contribute, and they also complain when something goes wrong in the planned schedule. These are the ones, whose attention is grabbed by other topics but have made some time for the community activities in their calendar, typically 2% to 5% of their time. And finally you have the “lurkers”, who actually don’t follow the community ritual, but participate just enough to be aware of what is going on. They also contribute a minima to maintain a feeling of social belonging, typically a few hours twice a year.”

Amygdala connection

The size of person’s amygdala either pre-determines, or is a consequence, (or correlates from some unknown reason), the size of persons social circle.

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