How many people can you meet in your lifetime, and could you potentially keep in touch with?
Hundreds?
Thousands?
Millions?
After all, there are people on Facebook with thousands of friends, or millions of instagram followers.
According to research by anthropologist Robin Dunbar, the number is actually likely closer to about 150 individuals.
This is approximately the number of people which one individual can keep ongoing relationships with.
Dunbar’s number was first predicted by Dunbar based on research he did on brain sizes of primates, based on how large the social groups of those primates were. The theory was that more complex social groups, where individual primates needed to keep track of more relationships and status hierarchies between members, would require more executive brainpower in the neocortex.
Based on the size of the neocortex in humans, Dunbar therefore predicted that an individual should comfortably be able to keep social relationships with about 150 other people.
However, closer personal relationships could only be held with a smaller number of people, as this requires not only more brainpower, but also time to develop and maintain.
In general, Dunbar’s research and that which followed it suggests that humans can easily keep up to:
- 5 close relationships (best friends)
- 15 good friends
- 35 – 50 friends at any one time
- 150 relationships
- 500 acquaintances
- 1500 people who you can recognise
Dunbar’s number of 150 people maximum has been found by other researchers in fields as diverse as how many other people users on Twitter interact with, tribe sizes during the Pleistocene and Neolithic, or even the ideal number of people in an office discovered by trial and error by innovative company WL Gore.
Yes, there may be a hint of selection and confirmation bias with examples being found that fit that number, but the core tenet still makes sense.
Of course, as we age and move, the actual individuals filling these positions is likely to change. After all, how many of us are still best friends with the same people we had in kindergarten?
It is also important to note that Dunbar’s number is one explanation behind biases like the “in group bias“. If we only have a limited number of people who we can keep acquaintances with, we evolved to prefer people who are similar to ourselves as this brought less uncertainty and more safety.
Dunbar’s number of 150 individuals is especially interesting when it comes to setting up teams and organisations. As companies grow and more people are recruited, at some point it becomes almost impossible for everyone to know what everyone else is working on, or keep up relationships with other. This is where administrative and bureaucratic processes begin to take over.
This is one of the reason why so many large companies find it challenging to innovate, when too many people are involved but the relationships are not clear enough for people to take ownership.
So if you want your company to be lean and effective at innovation, it may make sense to find ways to allow smaller teams of less than 150 the authority to try and do their best work.
Nick Skillicorn
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