First: check how many friends you have on Facebook. Next: ask yourself how many of them you consider to be ‘real’ friends? According to Dunbar’s number, we can only maintain about 150 meaningful relationships at one time. And you can probably count your closest friends on one hand.
How many real friends can we have? Image credit Helena Lopes via Unsplash
Your social brain
Robin Dunbar has spent nearly 50 years studying primates. Back in the 90s, he looked at the relationship between group size and brain size of different primate species. Specifically, a part of the brain called the neocortex, which is involved with conscious thought among many other things. Neocortex size turned out to be a good way of predicting how big a group monkeys and apes hung out in.
The next step was to apply this theory to humans. Dunbar came up with a clear prediction. Given our brain, at any one time, we should only be able to maintain genuine social relationships with around 150 people. Actually, the original number was 148 (with a confidence interval of 100 – 230) but over time 150 has become the magic number.
According to Dunbar, we simply don’t have the brain space – or time – to nurture social relationships with any more people than that.
Most monkeys and apes maintain their relationships by grooming each other. We don’t have time to groom everyone in our group – we’d starve in the process. Fortunately the evolution of language allows us to stay connected without spending hours grooming each other. But even with language, we don’t have the capacity to know and be known by more than 150 people.
Dunbar’s number
This prediction of 150 relationships has become known as Dunbar’s number. It’s also been referred to as the monkeysphere. What did Dunbar mean by a genuine social relationship?
The number of people you would not feel embarrassed about joining uninvited for a drink if you happened to bump into them in a bar.
There has been plenty of argument about how well Dunbar’s number holds up. And many researchers have criticised different aspects of Dunbar’s theory. But Dunbar’s number does hold true in a variety of situations.
Many traditional hunter-gatherer societies are around the 150-people mark and a 2002 UK study found on average, people sent between 120 and 150 Christmas cards.
A well-known story tells of Bill Gore (of GORE-TEX fame) discovering that his factories worked best if each was capped at 150 employees. Beyond that, people didn’t know each other well enough to work effectively together.
Enter social networking
It’s easy to imagine social networking sites have changed the landscape when it comes to how many friends we can have. We don’t need to even talk with, let alone groom, people to stay in touch. We can broadcast our news to hundreds or thousands of people in an instant. We can stay up-to-date with the lives of as many people as we have scrolling time for.
But a study of Twitter users found people could only maintain between one and two hundred stable Twitter connections. A study of 450 undergraduate students found that although many of them had 300 or more Facebook friends, they only considered an average of 75 of them as real friends. The average 18-29 year-old Australian has 394 Facebook friends.
Layer upon layer
More recent research suggests that rather than thinking about our friends in terms of a number, we should think about Dunbar’s layers. Most of us have around five intimate friends, including a romantic partner if we have one, and 15 best friends. Going out in layers, we have 150 friends, 500 acquaintances and a total of 1,500 people we can name if we see them. Researchers have identified these layers in people’s mobile phone use among other networks.
A 2016 study asked more than 3000 people for a bit more detail about their Facebook friends. On average, these people had between 150 and 200 Facebook friends. But when asked how many of those people each could turn to in a crisis, the answer was four. How many would offer genuine sympathy in a difficult situation? Fourteen.
The quality of our relationships are directly related to how much time we invest in them. And we simply don’t have time to invest in hundreds of friendships. That’s not to say our broad social media communities aren’t valuable, just that nothing beats face-to-face time for genuine relationships.
So next time you’re about to pick up your phone and open Facebook, maybe it would be better to give a friend a call and meet up for a drink instead. That’s my plan!
Dr Jen Martin 
This is terrific Jen – makes so much sense!
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Thanks for reading Matt. It does, doesn’t it. We all have only so much capacity!
Ah Jen – you’re back and on fire! Great kick off subject and I agree with the layering concept – it’s a neat way of looking at it.
Thanks Marti. So happy to be back. I’m sure it was meeting you that did it 😀