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Can I really have 300 authentic friendships

Can I really have 300 authentic friendships

Before you go any further, click over to your Facebook account. Now write down how many Facebook Friends you have. Next scroll through the list and record the number of people with whom you have a face-to-face relationship. Cut out people who are just friends of friends. Only count the number of people you would say hi to in the airport at 3:00 am.

What number did you get?

Robin Dunbar, an anthropologist and evolutionary psychologist, would guess that number at about 150. Dunbar's research looks at the mechanisms of social bonding in primates. If his name sounds familiar, it's because he is best known for discovering what we call the "Dunbar Number."

Our social brain

According to some scientists, the size of our brain is a result of the environmental challenges our ancestors faced. The human brain experienced the greatest rate of growth during the ice age, a time of extreme environmental change. This new, larger brain could process a greater quantity of information, as well as more complex data.

But Dunbar reasons that the size of the human brain evolved in response to the increasing number of complex social relationships. Antelope live in large numbers, but they don’t have large brains like humans and other primates. Dunbar believes this is because the complexity and intimacy of those herds are nothing like the social relationships maintained by primates.

In his research, Dunbar discovered a limit to the number of complex relationships an individual could maintain. It didn't matter if the individual was a rhesus monkey or a human. And that limit was directly related to the relative size of the neocortex.

The neocortex is part of the mammalian brain. It's involved in language, sensory perception, spatial reasoning, and cognition. Extrapolating from what he discovered of relational limits and neocortex size in lower primates, Dunbar estimated that humans could maintain about 150 face-to-face relationships.

This became the Dunbar Number.

More evidence

To prove his theory was sound, Dunbar needed more than extrapolation. He needed real world examples. And there are plenty.

Neolithic farming communities had about 150 members. Within the Army, the "unit" is the smallest independent group. It usually consists of 130-150 individuals. Roman armies were usually around 150 individuals in size.

Researchers have found that companies of 150 or less employees do not need management hierarchies. Instead these companies appear to function on personal relationships that support mutual obligation and cooperation. Once a company reaches the 150-200 employee mark, they must incorporate a management hierarchy.

Within traditional hunter-gatherer societies, people divide into many levels. The tribe is usually around 500 - 2,500 individuals. The tribe shares  a common language and cultural heritage. Temporary night camps make up of thirty to fifty people, but are unstable. Between these two, we find clans. These can form for ritually significant events like birth, death, and holidays. Or they from from common territory. A survey of twenty some tribal societies found that the mean clan size was 153.

This limit isn't a matter of what our brain is able to store in memory. It's more than remembering someone's name. Instead, it's about the complexity of the relationship. Who is this person, how do they relate to me, and how can I use my knowledge of this person to benefit me (remember evolution at work here).

You might be able to recognize 300 different faces and/or names. You may even be able to chat idly with that many people. But when it comes to important relational information, your brain just can’t handle more than 150 individuals. Would you walk up to all 300 people at 3:00 am in the airport and have a meaningful conversation?

Groups of three

Within this limit of 150, we create levels of intimacy. Our most intimate core group of relationships consists of 3-5 people. These are the people you can rely on during times of trouble. To maintain these core relationships, we should need to maintain contact at least once a week.

The next level up consists of about 10 people. Social psychologists refer to this group as the sympathy group. If you would be distraught if an individual died, they belong in the first two groups. Dunbar points out that this is typically the size of most sports teams, the number of Apostles, and the size of a jury. This group required contact about once a month.

The next level, about 30 people, and each successive circle seems to go up by a factor of three. To maintain these expanding levels, you should be contact at least once per year.

Sadly, it seems we only have so many slots on our relationship dance card. And only so many spots in each level of intimacy. If someone moves from the outer circle  to an inner circle, than a someone must shift up into a less intimate circle.


Friendships and the Dunbar Number

If you ever feel like it’s impossible to make a new friend, you might just be running up against the Dunbar Number. By the time we reach our forties, most of us have established our 150 people. Adding new people means letting someone go. For you and for the other person.

Of course, friendships fade without regular contact. So it’s not as difficult to find a spot in the outer circles. But if we crave more intimate relationships, we have to continue working toward the inner circles. Both people must be willing to shift folks that currently reside in the inner circles to the outer levels. You may be willing to shift your cousin Mary, but your new friend might be pretty comfortable with her two innermost circles.

Remembering that each of us only has so many people we can maintain close, complex relationships keeps expectations realistic. It doesn’t mean you’ll never make it into the inner circles. But it takes time, commitment, compassion, and care.


Dunbar, Robin. How many friends does one person need? Dunbar's number and other evolutionary quirks. Harvard University Press, Cambridge, Massachusetts, 2010.


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