The Anatomy of Friendship
on the social psych paper that changed my life
The Anatomy of Friendship is a literature review on human social psychology and the science of friendship. It’s an approachable sixteen pages long, and was published in 2017 by Robin Ian MacDonald Dunbar, an evolutionary neuroscientist at Oxford who has been studying primate relationships for five decades.
Dunbar is my hero and my prophet.
The most famous idea in Anatomy of Friendship is called “Dunbar’s number”. If you haven’t heard of this before, it basically says you can have only a limited number of friends (about 150), and that this number is materially constrained by time and social resources.
This notion of resource constraints is intuitive, but most people don’t stop to consider the gravity of this insight. Let's think about this for a moment:
In a day, you get 24 hours. You might spend 6-8 hours sleeping. You spend another 6-8 hours doing some kind of work. You spend 1-3 hours preparing and eating food. You might spend another hour or two grooming yourself and doing miscellaneous tasks, and you probably spend an embarrassing number of hours mindlessly consuming your social media vice of choice.
After accounting for all of these responsibilities, you probably only have a few hours left for quality time with your friends, family, lovers, and acquaintances. Even if you're hyper-efficient about maximizing your "relationship time", you probably don't have a long enough social battery to really capitalize on all of it. Even the most sociable people need a break eventually.
Anyway, the point is:
Your emotional capital is limited (time, energy, willingness to socialize).
You have to somehow distribute it between literally all the people in your life.
So there’s a hard ceiling on the relationships you can sustain, over the course of a day, a week, or a lifetime.
Unsurprisingly, not everyone has the same ceiling. A more extroverted person might maintain a large web of friendships, while an introverted person might spend his time with just a few friends.
Dunbar finds that most people can maintain about 100-250 friends, with an average of about 150. This is where we get his eponymous number—the headline usually goes something like: "They did the math; you can only have 150 friends!"
Of course, that’s the provocative clickbait version of the idea. In the real world it's a little more complicated. For starters, what does this guy think a friend is, anyway?
In the paper, Dunbar defines friends as "the people who share our lives in a way that is more than just the casual meeting of strangers [...] That includes members of our extended family as well as more conventional friends (i. e., people not biologically related to us); it also includes our romantic partners".
Using this broad concept, Dunbar's circles of friendship begin to take shape. Your social life can be arranged into a sort of bulls-eye configuration, where friendships fall into concentric circles that scale by roughly a factor of 3. The smallest circle contains 1.5 friends, and the outer ones contain 5, 15, 50, 150, 500, and 1500 friends, respectively.
Each of these rings represents a different type of friendship, arranged in order of intimacy and frequency of contact. Let's examine these circles, starting from the middle:
0 - Ego
Yeah, that's you. You can’t avoid yourself, and except for an occasional dissociative experience or some kind of Freaky Friday scenario, you're stuck in your own head basically all the time.
1.5 - Primary partner(s)
This is the one person (or sometimes two people) in the world to whom you're closest. In childhood, this person is usually a sibling or a very close friend. You spend a ton of time with this person, and as you get older you sometimes do crazy stuff with them, like getting married or having children.
You interact meaningfully with this person at least once a day.
5 - Intimate friends
This is your clique, your crew, your squad. Your closest confidants and a reliable source of emotional support. These might be your roommates, besties from school, or regular after-work drinking buddies. Think of these people as the 3-4 friends you might call if you had an emergency and your primary partner was unavailable.
You interact meaningfully with these people at least once a week.
15 - Best friends
These friends exist on the periphery of your circle of 5. They might be friendly coworkers, pick-up basketball teammates, or just friends you spend time with casually but not every weekend. You know them well, but probably wouldn’t call on them in case of emergency. Still, these friends play an important role in your social life, and you would specifically miss them if they moved away.
You interact meaningfully with these people at least once a month.
50 - Close friends
These might be friends who you wouldn’t make plans with, but whom you’d expect to see at a party. Typically, you know them well enough to have an extended conversation, and could describe their social relationships in some detail, despite not being inside their closest circles.
You interact meaningfully with these people at least once every 3-4 months.
150 - Just friends
Dunbar's number! These are people with whom you'd feel close enough to approach if you saw them at an international airport. They are sufficiently close to your social scene that you know about their interests and important relationships, but you otherwise don't spend much time together or share particularly vulnerable details with each other.
You interact meaningfully with these people at least once a year.
500 - Acquaintances
Typically this circle is filled with people who you once saw on a regular basis, but you don't cross paths anymore (e.g. former classmates, childhood friends). You know them, but you don't really "know" them.
You may have interacted with them meaningfully in the past, but you haven't contacted them in more than a year.
1500 - Names and faces
These are simply people whose names you could recall if you saw them in a picture, or out in public. Roughly speaking, Facebook friends.
You might have interacted with them at some point years ago, but you don’t remember much about them except their name or face.
I've sketched out the idea of (1) emotional capital and (2) Dunbar circles to hundreds of people, and most of them say it feels generally correct. It gets even more interesting when you investigate the numbers:
On average, people spend 40% of their social effort inside their 5-circle, and an additional 20% maintaining their 15-circle. In other words, you allocate well over half of your precious emotional capital to your closest 15 friends.
Here’s what this looks like in practice:
As time passes, you grow and change. You accumulate new interests and habits and ways of being. And as much as you might like to, you just don’t have the bandwidth to keep all your friends up to date on your recent fascination with professional bowling, or the newest viral Netflix miniseries.
This feels bad sometimes. But whether you like it or not, all of your relationships are subject to the relentless entropic drift of time. You simply don't have enough emotional capital to interact that often with everyone you'd like to keep inside your inner circles of friendship.
Sometimes, people tell me the numbers don’t seem right. They feel like they talk with their friends and acquaintances a lot more or less than Dunbar says. Despite having read this compelling Substack post, even you might even be questioning the plausibility of Dunbar’s model.
But you don’t have to take his (or my) word for it!
As a parting exercise, I invite you to draw your own Dunbar circle. All you have to do is make a list of your friends, then group them according to the nifty table below.
As you write your list, ask yourself:
Who do I meaningfully contact on a daily/weekly/monthly basis? How many people fall into each of my circles?
Where and how do these interactions take place? Who reaches out to whom? What is the content of these interactions?
How satisfied am I with the composition of each ring, and how might I make an effort to change it?
When have these circles been stable or in flux, and how was I feeling during those times?
This exercise might feel a little bit unnatural or pedantic, but I’ve found that it’s often a helpful way to reflect concretely on the current state of my social life, and identify the people I’d like to see more in the immediate future.