Robin Dunbar: Is There A Limit To How Many Friends We Can Have? Anthropologist Robin Dunbar believes the evolutionary structure of social networks limits us to 150 meaningful relationships at a time — even with the rise of social media.

Robin Dunbar: Is There A Limit To How Many Friends We Can Have?

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How many friends do you have?

ROBIN DUNBAR: I usually, at this point, say none.

RAZ: You have no friends.

DUNBAR: That completely floors presenters (laughter).

RAZ: Wait, how do you have no friends?

DUNBAR: Well, that's not true. It's just that I don't know.


RAZ: This is Robin Dunbar.

DUNBAR: And I'm professor of evolutionary psychology at the University of Oxford.

RAZ: Are you a networker? Do you go to parties and network and try to get numbers and cards and things?

DUNBAR: I try to avoid it as much as possible. I'm very old-fashioned.


RAZ: Are you are, like, an introverted Englishman?

DUNBAR: Absolutely, yes.


DUNBAR: I'm the archetypal (laughter) Brit here.

RAZ: (Laughter).

DUNBAR: Good heavens.

RAZ: OK, so even though Robin doesn't like talking about his social network, he's actually one of the world's leading experts on the topic. In fact, he's famous for coming up with a very specific number - a number that's basically the limit on how many friends people can have in their social networks. And it's literally called Dunbar's number.

DUNBAR: So Dunbar's number is the limit on the number of people that you can have meaningful relationships with at any one time. So I kind of like to think of it as all the people you might not feel embarrassed to go up to if you bumped into them at 3 a.m. in the morning in the departure lounge bar at Hong Kong airport. They would know who you are, where you fit into their social world. You know who they are and where they fit into your social world. So you might have some catching up to do because you haven't seen them for a while, but you wouldn't feel that you're intruding in any sense to go up to them.

RAZ: So it's a number of people that you can conceivably have some kind of relationship with.

DUNBAR: Yes, yes. And to be fair, that number really consists of a series of layers of increasing intensity of relationship quality. So you're really surrounded by a series of circles.

RAZ: OK, so Robin says you can think about your friend network a little like a series of concentric circles, with each circle representing a category of friends. So in the center, in the bullseye, you've got an inner core of about five of your closest people.

DUNBAR: What you might think of as intimate friends.

RAZ: Then the next circle out, you've got about 10 still very close friends.

DUNBAR: Best friends, maybe.

RAZ: Next circle - about 35.

DUNBAR: Good friends.

RAZ: Then you've got the rest of your not super close but still friendly with friends. Anyway, altogether, it adds up to...

DUNBAR: Hundred-and-fifty.

RAZ: Dunbar's number.


DUNBAR: Is this really true, that that's the size of our groups? The answer is yes.

RAZ: Here's Robin Dunbar on the TED stage.


DUNBAR: It turns out that the reason for that is it's a problem with your brain. And we've been able to show with neuroimaging studies - in a series of neuroimaging studies, the number of friends you have is essentially a function of the size of this bit of the brain up here, right above the eyes. What this allows you to do is to understand how other people are thinking, the state of their minds, as it were. And it's the number of individuals whose minds you can handle in this kind of way that seems to set the limits on the total number of friends you have.

And this was our attempt to first - very first attempt to look at what it meant for you as an individual. And we asked people to tell us who they were sending Christmas cards to, not the number of cards they were sending, but who were in the household, the total number of people in the household.

And that turns out to be very close to 150. The average in this state is that it was 154. There's a lot of variability around that. Some of us are incredibly mean and don't send any cards at all. Some people send them to their butcher and their baker and their lawyer and, you know, all those kind of important people. But the key is that it's, you know, nicely peaked here around 150.


RAZ: I mean, it's so interesting because I was thinking about our Christmas card list and it is about, yeah, it's about 150 people. But do we know if this number has always applied to humans?

DUNBAR: Yes. So I set about looking into the data on community sizes in small-scale ethnographic societies, and it turns out that yeah, that's actually a very, very common number. You get exactly the same number a thousand years ago as the average village size in England and Wales.

We know that from the "Doomsday Book" when, you know, William the Conqueror thought he'd better find out what he'd just conquered. So he did this complete census of the whole country. It's a wonderful resource, but it turns out the average village size in England and Wales was almost exactly 150. And when William the Conqueror divided his new kingdom up among his henchmen and his mates that came over and helped him out, it was to exactly 150 people.

RAZ: So what you're saying here is you can only have about 150 slots in your brain that you can fit friends into?

DUNBAR: Yes, but it's also partly about time. So we build relationships by investing time in them. The reason you get the layers is really a consequence of decisions you make about how to distribute the time you have available for social interaction.

And you end up investing about 40 percent of your total available social time in your five closest friends and family and then another 20 percent of your total available time in the next 10 people. And the rest get much thinner quantities of your time. But as you pass over that 150 boundary, it really drops to pretty much next to nothing.


RAZ: Robin started to come up with the idea for Dunbar's number in the 1990s, which of course was before a colossal change in how we keep track of our friend networks, which of course was Facebook.


DUNBAR: Particularly when Facebook came on stream, I think there was a kind of promissory note made on the tin can by the techies that created it, which said this is going to open you up to the global village. You're going to have hundreds of thousands of friends all over the world. And the real question is, is that so? The short answer is no (laughter).

Despite the fact that Facebook allows you to put 5,000 friends up on the can, as it were, in fact, most people don't. And if - as a result of sort of this discussion about who your friends are on Facebook, Facebook actually started to look at their own data.

And when they did an analysis of the entire whatever it is 400 million Facebook users and looked at all the numbers of friends people had, the average was actually about 150. The key to the issue is really even though you sign up and can sign up lots and lots of people, in fact you spend most of your time talking to only a very few of them.


DUNBAR: And indeed, what's more, I mean, we've shown this with Facebook data, as well as cellphone data. You can pick out these layers beautifully from the frequencies with which people post to each other, let's say on something like Facebook, or phone each other. And what's more, they're doing so at exactly the same rates as they would normally see them face to face in the real world.

RAZ: That's amazing. So basically, the way we have always interacted with other humans hasn't changed because of Facebook or social networks, digital social networks.

DUNBAR: It seems not. I mean, in some ways, it's not too surprising. If the problem is partly a cognitive one - you've only got 150 slots for friends and family, generally - the digital world isn't really going to change that. What the digital world might do - and what we sort of expected it to do, I have to say, when we looked into this initially - was it allowed you to be more efficient with your time.

So the big problem with the face-to-face world is it literally is face to face. So you have to sit there talking to somebody, and you can't often have a conversation with several people simultaneously. We thought the digital world would cut through because you can post to several people simultaneously, if you want.

But we kind of discriminate between meaningful exchanges where I'm posting directly to you, send you a private message or something like that, and our kind of Twitter use of social networking sites, which is a bit more like a lighthouse in the dark of a winter night. You know, who knows how many ships may or may not be passing by and actually see your signal and actually care about it. There's no real interaction going on there.

So it seems to be this sense that you are trying to communicate meaningfully with me that becomes important in establishing the relationship between us.


RAZ: OK, so I get that, like, we don't have more friends now because of Facebook, but it has made it more efficient to keep up with lots of people, right? And so in a sense, has that made us happier than our pre-Facebook, pre-computer ancestors?

DUNBAR: That's an interesting question, actually, as to whether we are happier now than we ever were. I suspect happiness in that sense has a lot to do with how well embedded you are into your network, how well you can keep contacting people. And clearly, I mean, the whole reason why Facebook and the other social networking sites have been so successful is precisely that in this mobile world, it's a great medium for keeping up with people after they've moved.

My only hedge on this is that in the end, that in a circle of five people, the reason you have them is that they're the people who will come to your support in times of great crisis. Now, the problem with that is if they're the other side of the continent, no matter how often you phone them, Facebook them, WhatsApp them or anything else, they're not right there sitting next to you to be the shoulder to cry on. Whatever you make of it, a shoulder to cry on has to be a physical thing.

So people who spend a lot of time on Facebook trying to keep up with friends who've moved are possibly losing out. You know, they might be better served by trying to replace them - or at least one or two of them - with people who are local, whose doors they can go around and knock on so they can cry on the shoulders of.


RAZ: So I've read that you are not on Facebook, right? Why?

DUNBAR: (Laughter) I'm just too busy. Well...

RAZ: It doesn't require much time. You just, you know, post something or not post something. It's...

DUNBAR: Yeah, it's, you know, it's very seductive, and I can well see why people do it. But at the end of the day, I would rather sit in a pub with a beer and a group of people and have a chat than write stuff on Facebook. It's just me (laughter).


RAZ: Robin Dunbar - he's a professor at Oxford University where he studies social networks. You can see his entire talk at


ANDREW GOLD: (Singing) Thank you for being a friend, traveled down a road and back again. Your heart is true. You're a pal and a confidant.

RAZ: Hey, thanks for listening to our show on Networks this week. If you want to find out more about who was on it, go to To see hundreds more TED talks, check out or the TED app. Our production staff here at NPR includes Jeff Rogers, Brent Bachman, Megan Cain, Neva Grant, Sanaz Meshkinpour and Casey Herman, with help this week from Chris Benderev, Camilo Garzon and Daniel Shukhin. Our partners at Ted are Chris Anderson, Kelly Stoetzel, Anna Phelan and Janet Lee.

If you want to let us know what you think about the show, you can write us at, and you could also follow us on Twitter. It's @tedradiohour. I'm Guy Raz, and you've been listening to ideas worth spreading right here on the TED Radio Hour from NPR.


GOLD: (Singing) Thank you for being a friend.

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