How to Leverage Dunbar's Number for your Community

Jul 1, 2021

Let's imagine you invited every single one of your Facebook friends to a party.

How many of those would you actually go up and talk to, or rather, want to go up and talk to and connect with properly?

Robin Dunbar reckons that for most people the number sits at around 150.

That's 150 meaningful relationships that we can maintain at one time. They sit just above your group of ‘friends’ and below your ‘acquaintances'. Dunbar’s research suggests that there are limits to our social groups and that numbers matter when it comes to community size.

The question is, can we use Dunbar's work to guide our strategy when it comes to growing our communities?

  • The human brain may only be able to maintain 150 meaningful relationships
  • When building a community, promote sub-communities as it becomes harder to maintain 1:1 relationships with community members
  • Use geography, interests, and member backgrounds for early sub-communities
  • Use available tools (below) to foster introductions between members
  • Dunbar’s Number may not be an exact science. Take it with a pinch of salt and adapt your strategy to what works for you and your community

30 years ago, anthropologist Robin Dunbar ran an experiment and found that the size of a certain part of the brain (the neocortex) in primates was related to the size of a social group that they were in. He inferred that there is a limit to how much social, tribal complexity someone's brain can handle. His magic number: 150 people.

Dunbar quickly went on to see if this translated also to humans. He uncovered that the hunter-gatherer group structure, which starts at family level and grows to community and tribe level, also came out to around 150.

Aside from the early hunt-gatherer, he found offices, factories, campsites, military organizations, 11th Century villages and even Christmas card lists also had their perfect size. Go over 150, and a community is unlikely to last.

It is important to note that the number 150 refers specifically to meaningful relationships with friends and family. Outside of these, Dunbar suggests we can have, on average:

  • 5 intimate relationships
  • 15 close friends
  • 50 friends
  • 500 acquaintances
  • 1,500 recognizable faces

Should you stop growing a community when it reaches 150 members? Of course not, but Dunbar’s research could help guide your strategy when it comes to dealing with growth.

The most valuable communities are those that are highly engaged, intimate, and foster meaningful connections. This becomes increasingly difficult as communities grow.

Here's what you can do 👇

Foster a culture where smaller communities can be built

If you don’t have systems in place to allow smaller sub tribes to join forces and find their meaningful connections you could lose members. No one wants to feel as though their presence is lost in a large crowd.

I'm sure you've seen Slack communities where there are channels with thousands of members that wind up with nothing but spam. As membership grows, intentionally designed sub-communities are essential to maintaining a feeling of intimacy. Here are a few ways to do it:

  • Geography -> i.e. a place for people from Miami, another for Seattle, etc.
  • Shared Interests -> i.e. a place for people interested in newsletters, etc.
  • Shared Backgrounds -> i.e. a place for engineers, another for designers, etc.

At Launch House, we created channels for the major cities where a meaningful portion of our members spend their time. We've already seen results in just a few weeks — people from different LH cohorts have become friends and organizing IRL events together.

Don't Wait for 150 Members

Some of your members, maybe even some of your most engaged ones, may spend time in 10+ communities, or considerably more. They'll become allergic to noise sooner than other members. For them, small group intimacy is more important.

Create Meaningful Introductions

Individual bonds are the best way to foster intimacy in a community.

Tools like intros.ai and Covalent use advanced data science methods to facilitate the best matches within your community from members.

Dunbar has his fair share of critics and I would not recommend blindly following one man’s analysis. His experiment was reproduced by others and they came up with quite different results (approximations of average group sizes between 69–109 and 16–42).

Overall, the research suggested that applying one number is futile. Everyone's brain is different, and factors such as diet and nutrition also affect brain size. Saying that there's one number to use for understanding most human relationships is overly simplistic.

Other researchers claim Dunbar is more interested in marketing than science. His original experiment implied 148 as the ideal number, which he rounded to 150. It's certainly easy to follow and implement, but does it really work for all situations and people?

Probably not.

Dunbar has since noted that his range should be taken more as 100-250 mark and highlights that there will always be differences when it comes to factors such as sex and age or whether people are introverts or extroverts.

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