Where is the New Dunbar Limit?
Michael Wu, Ph.D. is Lithium's Principal Scientist of Analytics, digging into the complex dynamics of social interaction and group behavior in online communities and social networks.
Michael was voted a 2010 Influential Leader by CRM Magazine for his work on predictive social analytics and its application to Social CRM.He's a regular blogger on the Lithosphere's Building Community blog and previously wrote in the Analytic Science blog. You can follow him on Twitter at mich8elwu.
Last week we learned about the relativity of tie strength and the attention economy. I’ve kept the discussion at a rather theoretical level, so I didn’t discuss how any of these concepts apply to a business or an organization. Well, this time, I hope to demonstrate their utility with some applications. Let me start with attention economy.
Attention and Relationship
You will recall that people’s attention is not only a finite and limited resource, in an information-rich society, such as ours, attention is actually a scarce resource. This is because we are under a constant bombardment of information, and attention is required to process, consume, and retain the information around us. Much like a computer that has finite information processing power, the limit on our attention is direct result of our brain’s cognitive processing power. (Coincidentally, my PhD lab is actually a neuroscience lab that studies visual processing and attention.)
The attention economy limits the number of active engagement that we can hold at any given time (within our immediate engagement circle). Since strong ties will tend to win our attention and dominate our social engagement, this takes attention away from the weak ties that we create, making it harder for them to develop into strong relationships. Therefore, the attention economy will indirectly limit the number of strong relationship that we can maintain. The natural question that follows is “what is this limit?” In other words, “how many strong and stable relationships can we maintain realistically?”
Understanding the Dunbar Limit
In 1992, Prof. Robin Dunbar estimated a theoretical limit on our ability to maintain stable relationship based on neocortex size (i.e. the cognitive capacity) of human brain. This limit became what is known as the Dunbar’s number (or Dunbar limit), and it has a value around 148. That means any individual can only maintain roughly 148 stable relationships on average, where they know everything (with respect to social relationship) there is to be known about these 148 people.
- Dunbar number applies to groups that have very high incentive (e.g. survival) to maintain social cohesion. In these groups, Dunbar speculated that 42% of the time budget is devoted to “social grooming” (for non-human primates, or socializing for humans) so that everyone knows everything about everyone else’s social relationship.
- Dunbar estimated his number with brain size data and group size data derived from 38 different primate species. Then he survey many pre-industrial villages and tribes and found their size all hover around his predicted number of 148.
That means Dunbar’s result may not be valid under the following conditions:
- In today’s society, where the incentive and necessity for social cohesion is substantially lower.
- In post-industrial era, where communication (an important part of socializing) is much more efficient than the pre-industrial era.
Beating the Dunbar Limit
How can we beat the Dunbar limit? Well, this has happened through the course of primate evolution. The Dunbar limits for other primate species with smaller neocortices are lower than that for human. Aside from developing a larger neocortex, how did we (human beings) beat other primates in terms of our ability to maintain social cohesion?
Dunbar proposed himself that language was developed as a form of social grooming that allowed early humans to maintain social cohesion more efficiently. The evolution of language reduces the time needed for human to socialized, bond, understand each other, and resolve conflicts. All of these activities are crucial for maintaining a social cohesion within a group. The evolution of larger neocortex, which enable language processing, ultimately lead to the larger average group size (148) compare to other non-human primates.
However, the human brain hasn’t changed much structurally over the past three hundred years from the pre-industrial to pre-social-media era. Primate neocortex size changes very slowly. The time required for this to happen is an evolutionary time scale, in the order of millions of years. So our cognitive processing power and our attention limit probably didn’t change over the past few hundred years, and it will probably remain the same for hundreds and even thousands of years in the future.
Armed with this information, there are two ways to beat the Dunbar limit.
- We can maintain more ties at the expense of weaker tie strength for each relationship.
- We can make socializing more efficient, so it reduces the time and attention needed to develop and maintain a relationship of equal tie strength.
Note: we will only discuss the first mechanism for beating the Dunbar limit today, and save the second mechanism for next week.
The Attention Economy and the New Dunbar Limit
Since our brain, specifically the neocortex, hasn’t change, the limits of our attention and time resources remain the same. Therefore, when we maintain more relationships, each one will get a smaller piece of the attention pie. Since the strength of a relationship is directly related to the amount of time and attention devoted to it, this usually leads to a weaker relationship (though not always, because there are other components of a relationship: intensity, trust, and reciprocity). So the important question that we should be asking is “whether or not we can get by with weaker relationships?”
We can! Although we have not dramatically evolved biologically as a species, our society has evolved. That is, even though our brain (i.e. neocortex) hasn’t changed, our society has changed. We have developed government, law, social etiquettes, and many social infrastructures that make our world a safer place to live. Consequently, super strong relationships are probably not as vital to our survival in the modern society, unless there is a war or some natural disasters. So there is less incentive to build and maintain super strong relationships. As a result we can get by with weaker ties that require less time and attention for their maintenance. This can certainly increase the number of stable relationships that we can maintain.
So what is the new Dunbar Limit? A new estimate for the average size of personal social networks has been investigated recently by Prof. Russell Bernard and Prof. Peter Killworth. This new “Dunbar limit” is roughly 291 at the height of the information revolution (before the dot.com bust). It almost doubled the original estimate by Dunbar for the pre-industrial era. However, the Barnard-Killworth estimate was derived from data prior to the social media revolution. Now, 10 years later, could the advance in social technologies today push this limit further? This is the topic of discussion for the next post. If you are interested, stay tuned and come back next week.
Alright, we’ve covered a lot of concepts. So, what have we learn today? I certainly hope that I’ve given you a deeper understanding about the Dunbar’s number. We’ve discussed how Dunbar estimated it and when it is valid. But the most important thing that you should remember from today’s discussion is that there is an inherent tradeoff between the number of ties we maintained and the strength of these ties. This is because humans today are still the same humans hundreds of years ago, and the cognitive processing power of our brain is fundamentally still the same.
Next time we will discuss the second mechanism for beating the Dunbar limit. In the mean time, I welcome any kudos, comments, critiques, and any further discussion about this topic. My last post has been very quiet: no comments, and only two kudos . I hope that doesn’t mean you readers our there are not interested in my work anymore. If there is something that you like to see, please do let me know. Honestly, I’ve been busy myself too. After coming back from my two week vacation in Japan, I barely have time to eat and sleep. I sincerely apologize for not being as engaging on twitter as I used to be. So I am working hard to catch up with my works, and before you know it, I’ll be back tweeting!
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