100 Things You Should Know About People: #30 — Our "strong tie" group size is 150 people

Collage of facesEvolutionary anthropologists study social groups in animals. One question they have been trying to answer, is whether there is a limit on how many individuals different species have in their social group. Robin Dunbar studied the relationship between brain (neo-cortex) size and the number of stable relationships that a species had in their social groups. Based on his findings with animals, he extrapolated to what the number would be for humans. Called “Dunbar’s Number”, he postulated that 150 people is the social group size limit for humans. (To be more exact, he calculated the number at 148, but rounded up to 150. Also there is a fairly large error measure, so that the 95% confidence interval is from 100 to 230 – for you statistical experts out there).

A limit to stable, social relationships — The limit specifically refers to the number of people that you can maintain stable social relationships with. These are relationships where you know who the person is, and you know how each person relates to every other person in the group. Dunbar has documented the size of communities throughout different geographic areas and throughout different historical timeframes, and he is convinced that this number holds true.

Across time and cultures — Dunbar assumes that the current size of the human neocortex showed up about 250,000 years ago. So he started his research with hunter-gatherer communities.  His observations include: Neolithic farming villages averaged 150 people, as did Hutterite settlements, professional armies from the Roman days as well as modern army units.

Intense survival pressure — His claim is that 150 is the group size for communities that have a high incentive to stay together. If the group has intense survival pressure, then it stays at the 150 member mark. He also notes that these groups are usually in close physical proximity. If the survival pressure is not intense, or the group is physically dispersed, then he estimates the number would be lower.

Too high or too low? — Some critics of Dunbar’s number say that the number is too high, and others that it is too low. In the world of social media people have 750 facebook friends or 4,000 twitter followers, showing that the number of 150 is way off the mark. A Dunbar fan would respond that these are not the strong stable relationships where everyone knows everyone and people are in physical proximity. Some critics say the number of 150 is too high – that the number of people one is close to both physically and socially is much less than 150.

It’s the weak ties that are important?– In a recent blog post Jacob Morgan says that what’s really important in social media is not the strong ties that Dunbar talks about, but the weak ties – relationships that do not require that everyone knows everyone in the group, and that are not based on physical proximity. He argues that the reason that social media is so interesting is that it allows us to quickly and easily expand these “weak” ties, and that those are the ties that are most relevant in our modern world.

Substituting weak for strong — I think both Dunbar and Morgan are right. It’s critical that we pay attention to that 150 number for our “survival” community in close proximity. If we don’t feel we have that “tribe” near us it causes us to feel alienated, isolated and stressed. Perhaps one of the reasons social media is so popular, and so many of us rely on Facebook and Twitter is that we don’t have a strong tie tribe. Although the weak tie network of social media helps us to feel connected, we’ll eventually feel let down if we try to have it substitute for a strong tie Dunbar tribe.

For more information, I suggest you watch this interview of Robin Dunbar:

http://www.guardian.co.uk/technology/video/2010/mar/12/dunbar-evolution

And read Jacob Morgan’s blog post:

http://www.socialmediatoday.com/SMC/169132

What do you think? Do you have a strong tie tribe network? Are you ultimately trying to substitute with your weak tie network? In our modern world is the weak tie network more important?

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