Transcript of Episode 140 – Robin Dunbar on Friendship

The following is a rough transcript which has not been revised by The Jim Rutt Show or by Robin Dunbar. Please check with us before using any quotations from this transcript. Thank you.

Jim: Today’s guest is Robin Dunbar. Robin is an emeritus professor of evolutionary psychology at Oxford University and his research is concerned with trying to understand the behavioral, cognitive and neuro endocrinological mechanisms that underpin social bonding in primates in general and humans in particular. He’s best known as the proponent of the Dunbar number. That is how cognitive limits and agent dynamics limit our capacity to friendship to approximately 150 people. He’s also known as the proponent of the view that gossip and social grooming, more generally, were key drivers in the evolution of human language. Welcome to the show, Robin.

Robin: No, great to be here.

Jim: Yeah. I’ve been following your work loosely for a number of years and, in fact, in some of the work I do in the social change area, that Dunbar number is talked about a lot, probably understood a little less than it could be, and so it was a really welcome opportunity to jump into your work in more depth and learn more about it. To that end, I recently read your new book, titled Friends, Understanding the Power of our Most Important Relationships, and it hits on the things we talked about and where your research is focused but also goes considerably off into other areas as well. It’s extraordinarily interesting and it was fun to read because you had lots of little asides, right, about the history of the Dunbars and how the McDonald’s are kind of generic Scotsman and all kinds of interesting things.

Robin: Well, life is full of these one thing leads to another streams of thought. The world is full of interesting facts.

Jim: Yeah, and I like the fact that you didn’t edit all those out. Too many academic authors say, “Oh, I can’t put all that stuff in there, it doesn’t sound professional.” Well, it actually makes it much more enjoyable. I recommended the book to my wife this morning on those grounds of lots of good content and pleasurable to read. What more can one ask, right?

Robin: Exactly, exactly.

Jim: All right, let’s get down to it. One of the things that was interesting and I think important for our listeners to understand your work is that you define friendship fairly broadly, right? When you say friends, you include relatives, romantic partners and even pets. What do you see as the fundamentals that unify these different classes into an intelligible grouping?

Robin: I guess they are all relationships you have that have meaning for you, that’s the essence of it. They’re individuals and of course that may well include your pets if you have special pets, who you put down your mug of tea and go off if they asked you and helped them out, is basically what it is.

Jim: It’s interesting because I’ve never really thought of pets in that same class but yet we’ve always had very close relationships with our pets and particularly our last one, it just passed away last September, he belonged in our ring of five. He actually did, right?

Robin: I’m sure he did, yes. And, boy, when they tap you on the knee and say it’s time to go walkies, you put down your book and off you go.

Jim: He was particularly interesting in my wife would be trying to do something on her computer and he’d come up and nudge her mouse hand and say, “No, no, no. No more computer. Time to go for a walk.” Or, “Time to go chase birds.” Another one of this favorite activity, right? Not that he ever caught any but he put the fear of God in them, that’s for sure. Any birds that were black and we concluded this was because when he was a young puppy and he had a bone in the yard, a crow came down and was pecking at the marrow in his bone and, hence forth, he did not like ravens, did not like crows, and he did not like vultures.

Robin: I tell you, the world is full of these people who will try and steal your bone from you.

Jim: That is true and you got to be prepared to run them off. The first thing that you dig into is how important friendship and friendship type relationships are to human wellbeing. In fact, you say this, loneliness is turning out to be the modern killer disease, rapidly replacing all the more usual candidates, as the commonest cause of death. And I love this, this is probably my favorite quote in the book, “It will no doubt get me into trouble with the medical profession but is not too much of an exaggeration to say that you can eat as much as you like, drink as much alcohol as you want, slob about as much as you fancy, fail to do your exercises, and live in as polluted an atmosphere as you can find and you will barely notice the difference. But having no friends or not being involved with community activities will dramatically affect how long you live.” Tell us more about that and how do we know this?

Robin: Well, I think it’s one of the kind of big surprises of the last 10, maybe 15 years has been the absolute avalanche of medical studies. In fact, showing, essentially, exactly this effect, that the single most important factor affecting your psychological health and wellbeing, even your physical health and wellbeing, indeed even your likelihood of dying into the future, is just the number and quality of close friendships that you have and it always comes out ahead of all the usual things that your friendly neighborhood doctor worries about on your behalf. That’s, of course, to be fair, one shouldn’t ignore one’s doctor’s advice at the best of times but there is a-

Jim: At least not entirely, right?

Robin: There is a sense in which the overload on the health system probably everywhere in the world, certainly in Britain here, would be massively reduced if the problem of loneliness was solved because that actually not only causes most of the visits to GPs, they just want somebody to talk to and the doctor’s the only person who will keep seeing them. But also loneliness really kind of sets you up for all sorts of consequential psychological and physical diseases. You’re much more likely to become depressed and develop Alzheimer’s and even sort of physical diseases like heart conditions and cancers if you are lonely than if you are surrounded by friends. And, of course, friends here includes close family but it’s those kind of five maybe core friendships, we sometimes call the shoulders to cry on friendships because they’re the ones that will put their coffee down and come to your assistance and aid and [inaudible 00:06:47] when you ask for it, which is, of course, more than most other people will consider doing. Those inner core friends really make a big difference to your sense of wellbeing, your engagement with life in general and, through that, there’s knock on consequence for your physical health, it’s extraordinary.

Jim: Yeah, it was very interesting. In fact, you quoted some work from Christakis and Fowler’s work using the famous Framingham study, where they follow everybody in the town of Framingham, Massachusetts. I used to live not too far from there. And they found all kinds of things and one of the things I thought was quite interesting is that you can think of friendship, they found you can think of friendship, as a network effect, right? That if your friends become more happy, you will too.

Robin: Absolutely.

Jim: Your friends get fat, it increases your probability, right? I’ve been a bad influence on some of my friends, I suppose, in that regard. Maybe you can tell us a little bit more about that, the friendship network as a propagation mechanism for behaviors and even health conditions.

Robin: Yes. Well, I guess it’s one of those mysteries of science really but the good folk of Framingham never anticipated how famous they would become but famous they all are and we thank them for it. But, yes, this Framingham study really was quite [inaudible 00:08:02] because they’d been following that community out for many decades, which allowed Nick Christakis to kind of look at the consequences of changing patterns of friendship, as it were, for your psychological and physical health and extraordinary things like how likely you are to give up smoking, if your closest friends gave up smoking, you were likely to give up smoking. If they changed their diet and ate far too many hamburgers, you would follow suit and, of course, all the disadvantages of physical wellbeing that follow from far too many fast foods. A remarkable study really and in the quantity and quality of information it’s given us but it really is a very striking effect, your best friend has an enormous effect on your wellbeing and physical and mental wellbeing and your friend’s friend also has an effect and, indeed, your friend’s friend’s friend even has an effect on you. There’s a sort of ripple that sort of spreads through the community and binds us all together in this.

Jim: Yeah. It shows how important these friendship networks really are and it kind of makes sense from our evolutionary history, which we’ll talk about later. In terms of this loneliness epidemic we hear about, I did a quick google this morning to see what I could find and I found a Harvard study that said 36% of respondents reported serious loneliness. 36% feeling lonely frequently or almost all the time or all the time in the four weeks prior to the survey, that’s a big ass number. This included 61% of young people aged 18 to 25 and 51% of mothers with children. That was shocking, shocking to me, particularly the 61% of young people 18 to 25. I remember back in ye good old days, long God damn time ago, when, man, your whole life was nothing but sociability at that age. Something must’ve changed.

Robin: I can see you’re a party animal, Jim.

Jim: I [inaudible 00:10:09] in my spent youth but I am now a calm and sedate older gentleman.

Robin: Very good. Yes. No, I think in a way, this has been the big kind of shocker in many ways of the last, well, couple of decades really, that the kind of 20 somethings generation seem to be developing this extraordinary kind of pandemic of loneliness and I think it’s because what’s happening is where you grow up and where you go to school, to university, you’re kind of wrapped in a cocoon of a community, either your home community, school community or family, extended family community and so on, or when you go to university, you are in a dorm with a bunch of guys and your kind of naturally sort of made community there provided for you, if you like.

Robin: And then suddenly, after you graduate, you get a job on the other side of the country and then you keep being moved on, either because you get fed up and change jobs or because your boss says, “Hey, we could do with somebody at our office in Florida. Do you want to go down there for a bit?” You are sort of thrown in at the deep end into environments where you literally know nobody and, of course, this is the big problem with the big cities of our modern world, is they are kind of social deserts really. If you don’t know anybody, you are kind of left high and dry because you don’t know where to go to meet people. The only place you know is the office and you don’t necessarily want to spend all day with these people in your office and then have to spend all evening and weekend with them as well but you end up with this sort of age group who, until they find their feet in that local community, which can take many years to do, I suppose we all know, who have been in that situation.

Robin: You have this troph of loneliness which you have to work through and it’s kind of not good for the person, it’s not good for the employer, because a lonely person who gets depressed isn’t going to be a good worker at their desk for you from Monday to Friday. I’m kind of surprised that employers haven’t really made bigger efforts to kind of try and bed their new recruits in in this kind of way. Maybe the Silicone Valley people have been more successful at this perhaps because they themselves have all been that age group so they kind of realize what the problem is but, yeah, no, it’s a big problem. Of course, the other end of life, then you get the same problem because what happens there is as your friends move away or, worse still, die off, you just don’t have the motivation or the energy anymore to go out to places where you might meet new friends to fill those empty slots so you tend to find peoples social networks sort of shrink once they’re past the 70 mark and it gets worse and worse. You sort of eventually end up back where you started, knowing only a couple of people immediately close to you, as it were.

Robin: And, of course, that just increases the levels of depression and the susceptibility to diseases of all kinds and then the third group, which you’ve mentioned, is the young moms stuck at home, particularly with first babies, I think, because obviously first baby is a bit of a trauma for all of us, of both sexes here, this sort of how do you do this kind of stuff. What do you do when the baby cries? You get a bit more experience, you get a bit more laid back with dealing with those kinds of things, but that first baby, you end up being locked in at home unable to go out so much. Obviously babies are very demanding things in their first couple of years and require a lot of attention from you and they’re exhausting so you kind of don’t even feel like going out, even if you got the opportunity and the knock on consequences of that, if you are not living in your home community where you’re surrounded by mothers and mothers-in-law and sisters and cousins who come round and help you out and have a coffee with you. If you’re on your own and your partner’s off out at work all day, it’s a long lonely furrow that you’re ploughing there and, of course, increases the risk of depression and all these other kinds of psychological sort of ill states, as they say.

Jim: Yeah. And, of course, at least in the States, this kind of phenomenon of the people who move away from their own community is principally a fact for the university graduate crowd, not necessarily for everybody else and, in the US, your typical non college grad still lives within 20 minutes drive of their mother.

Robin: This is true.

Jim: And that’s important to note, this is a class based thing.

Robin: Yeah, and I think you realize how difficult childcare in particularly that first year of the baby’s life, how much more difficult it is for people who’ve moved away from home and don’t have the support of their kind of home family and home community. I think they struggle much more, even if they don’t suffer from loneliness and depression.

Jim: Yeah, that’s an interesting thing to think about and how we organize our society, we’re probably not doing a very good job of increasing human wellbeing. We’re not paying that much attention to it, as you point out.

Robin: I think that’s a lot of the problem. Of course, our evolutionary history, we’ve spent most of it in very, very small, fairly stable communities, not to say that people didn’t move. After all, the great majority of the citizens of the United States have their origins from people who up sticks and cross the Atlantic in search of a better life, as they say. Once you’ve got established somewhere, even then, you would end up in a fairly small, quite close knit community, which provides you with a lot of support in all sorts of psychological and social respects that are very important to the way we deal with life, in general. Our success, as a species, owes its origins to the extent to which we’ve been able to form those kind of self help communities.

Jim: Yeah, at some level, the human superpower is cooperation at various scale.

Robin: Indeed so, indeed so. Indeed so.

Jim: Let’s change topics a little bit, you quote some work from John, let me get his name right, Cacioppo about claims that neuro modulators are an important aspect of these kinds of things and may suggest an evolutionary dimension that loneliness has got some attributes with our genes, essentially, and you talk about some specific neuro modulators and you even have some specific views contrary to popular culture on our good friend, oxytocin. Tell us a little bit about your thinking with respect to neuro modulators, friendship, loneliness and all that.

Robin: Yeah. I think the key point about what John Cacioppo was saying was simply that feelings of loneliness are kind of an evolutionary alarm bell really. Something’s not going well in your social life, get out there and do something about it rather than being, itself, a condition or disease, if you like. It’s really just a signal from your bodily system to say, “Things are not good in here. We need some bolstering so get out and meet some folk.” And in that sense, it’s a signal of the fact that all sorts of other things are going on that lead into these various psychological illnesses or conditions, depression and so on, or indeed physical.

Robin: And one reason for the physical side effect is that loneliness and depression sort of negatively affect your immune system so the body is not so good at seeking and destroying all the viruses and bacteria and whatnot that the external world insists on throwing at us all the time and the immune system is clearly there to protect us from those but if your immune system is suppressed because you’re depressed because you’re lonely, then you’re going to suffer much more from all these many diseases from sort of irritating winter colds right through to the serious stuff, as a result. And I think that makes a lot of sense, from an evolutionary point of view. Now, where were we going on the second point?

Jim: Yeah, the neuro modulators and how does that play into the story, the serotonin, beta endorphin, dopamine, that stuff?

Robin: It actually turns out that there are some quite important differences in how the brain is organized and the size of different bits of the brain between people who are naturally social isolates, who are commonly lonely as a result, and people who are very intensely social. There is something that goes … And this appears to be related to some aspects of our genetics as well so it’s not entirely a consequence to the environment and experiences you have, there is a genetic component to that, and part of that may relate to … This connection hasn’t been kind of worked out exactly but it may well relate to the role of some of the key neuro modulators in this whole business of friendship versus loneliness. Now, there’s been a kind of media frenzy and, to some extent, a research frenzy over this little neuro peptide, oxytocin.

Robin: Oxytocin’s very interesting because it actually is very ancient. It evolved in fish to maintain water balance within the body so that the body didn’t get completely swamped with all the water coming in, seeping in from outside, and then it got sort of switched into the reverse pattern with the evolution of mammals because our problem, once the fish, if you like, colonized the land, they have the reverse problem of trying to keep the water in, rather than it being sort of seeped out with the drying environment on land. And so, we all have it and it serves these very important functions of helping to modulate the body’s fluid balance, if you like, but it was co opted by mammals in particular for use in mother infant interactions because obviously lactation involves a huge amount of pressure on the water content of the body, as it were. Milk is 95% water basically so this maintaining water balance while your lactating then becomes very important and oxytocin’s tied up with that and it’s sort of being co opted as a coming popular parlance to be referred to as the love hormone because it seems to prompt these very positive eternal feelings of love for one’s offspring as a result of giving milk to babies.

Robin: And a lot of that kind of interest emerged as to whether this was actually the kind of core chemical involved in generally social relationships among, obviously mammals in general, but humans in particular, and it spawned a huge amount of interest. Not always terribly well thought out experiments, I’m afraid, in some cases, but it’s true that it does have work in the way I suggested. It’s very important in mother infant relationships and it works in terms of romantic relationships, which you might argue are kind of indirectly related to each other for the obvious reasons that you can’t have babies without having romantic relationships first. But in terms of what kind of makes the social world go round, at least in primates, it appears to be another, and in fact much more powerful, neuro peptide in the brain, the endorphin system, particularly the beta endorphins, and these appear to kind of underpin the building of friendships, essentially.

Robin: Now, endorphins, like many other chemicals, they’re neuro transmitters in the brain, they seem to be involved in many different functions but the beta endorphins in particular seem to be involved with the pain system. They are extremely good analgesics. In fact, weight for weight, beta endorphins are 30 times more powerful analgesics than morphine is. The short answer here is, or the short lesson is, don’t take all this artificial stuff, just get your own morphine, your own endorphins going. They far, far better and they make you feel good.

Jim: How do we do that?

Robin: Well, in terms of our primate ancestry, the endorphin system is triggered by physical contact so stroking and patting and cuddling and so on. This is just primate grooming. When you see monkeys in the zoo leafing through each others fur and picking bits out, what they’re actually doing is triggering the endorphin system in the brain through a fairly complicated but unique neuro system that only responds to light, slow stroking and we have that neuro system, we can trigger it with stroking and cuddling and so on and the way we do and of course that’s why that system is still embedded in very close relationships but it kind of doesn’t work for large numbers of people at the same time because you can only cuddle one person at a time. I’m always inclined to suggest, if you don’t believe me, try cuddling two people in the back row of the cinema, when we’re allowed to go back to the cinemas again, and I would hazard a guess that within about five minutes, one will have left in a huff and be rather cross.

Jim: I don’t know what my wife would think about me trying that experiment but we’ll see if the opportunity ever arises.

Robin: Yes. And that’s because you’re not paying attention to them and there’s something very intimate about physical touch that involves real focused attention and, if you like, meaning in the relationship. And of course, that’s not what you want for bonding bigger groups. What we found, historically, is a number of ways of triggering the same neural system, at least at the brain end, and triggering the release of endorphins in the brain, to create this sense of calmness and relaxation and trustingness and happiness, that the endorphins give us and make us feel bonded to the people we’re doing these activities with and these activities have probably, in the following order, been co opted by our ancestors who [inaudible 00:25:50] former in our core part of our social tool kit and they are laughter, singing, singing without words, probably originally, dancing, playing of music obviously, feasting, eating and drinking alcohol-

Robin: Obviously feasting, eating and drinking alcohol together, telling emotional sob stories and many of the rituals of religion. All of these we’ve been able to show, trigger the endorphin system and they make you feel much more bonded to the people you do them with. And they have the advantage because you don’t physically have to touch the other person, it gets over that intimacy hump as it were, which means you can bond with many individuals simultaneously. Then of course, if you’re doing things like singing, or I keep suggesting somebody tries to see how many people you can get in a line dance together. But the synchrony of the behavior that you get in those contexts means that you can create this sense of community with very, very large numbers of individuals. We’ve done it with up to 200 people in a choir, it works extremely well. Choirs of 200 get more bonded by singing together in choirs of 22, for example.

Jim: Very interesting.

Robin: So there are booster effects that come out of it. But what seems to be important in there is the synchrony of these behaviors. And if you think about a lot of these activities that I’ve mentioned, most of them are highly synchronized. When we laugh, we laugh in synchrony with each other. When we dance, obviously we dance in synchrony. When we sing, of course we sing in synchrony. Many of the rituals of religion, you stand and kneel and sit and cross yourself or whatever it is that you do in your religion, all at the same time. Somehow that ramps up the endorphin output, but we don’t really understand why it does that, but we get it from exercise. If you go jogging with people, A, you’re likely to be running in synchrony with, so you hear that from the footfall being coordinated between people. That seems to ramp up the endorphin effect compared to if you went on your own. So you’re getting an extra boost, as it were, from the exercise. So the message is, don’t go jogging on your own, go with a friend.

Jim: Yeah. I really like this list. I think of laughter singing, dancing, playing music, drinking alcohol, feasting, it all fits in the bucket of conviviality essentially, right? All the good stuff in life.

Robin: Indeed so, at the end of the day, this is why we do those particular activities in social context. If we want to engage with people, what we do is we try and engineer it so that we can do one or other of these activities or several of them at the same time.

Jim: Even alcohol, think about clinking, the mugs and bottoms up together, right?

Robin: Yes, yes. Absolutely so. And if you think about when we… Okay, if you grab a sandwich on the street and eat it on your own, that’s one thing, satisfies your hunger maybe. But if we sat down to a social meal, a social dinner with friends or people, we want to get to know, everything is very ritualized so we do things at the same time. The courses come at the same time as it were and provide moments of synchrony through the meal. We will engage in the odd toast maybe, so again, somebody is the master of ceremonies there, is regulating the drinking that you do, so you all do it at the same time. Somebody perhaps tells stories or tells jokes and makes us laugh and we all laugh together or we all sob together. These are the secrets of a good social interaction and a good social life, really. So perhaps it’s not surprising that they’re the ones we use, and we don’t sit in silence with each other.

Jim: Although of course today, we’re more likely to sit in silence and be typing angrily into Facebook, asynchronously.

Robin: You may say so, I couldn’t possibly comment.

Jim: Truthfully, I’m currently [inaudible 00:30:10].

Robin: That’s part of the problem I think is that we spend so much time sitting in isolation in our rooms at the end of a keyboard where we don’t, at the same time, have the social controls that would normally prevent us flying off the handle. So if somebody in a conversation said something that mildly outraged you, you would either sort it out with them and have a discussion about it and come to some mutual agreement, or somebody tell a joke and break the tension. But there you are in the loneliness of your room, you hit the keyboard and say things which in a social context you would never do because you would pick up the negative vibes that start to spill out as you start to say something to express your outrage at whatever’s just being said. You would pick up these vibes that not everybody’s happy with what you were saying, so you backtrack and modulate what you have to say.

Robin: And this is really the key to social life, is this ability to see the world from somebody else’s point of view and find some kind of compromise between your opposing views. So it’s all the skills of diplomacy actually, conspicuously not there in the diplomatic circles very often, but there we go. And they’re what makes social life at the level of the humble individual work, because if you’ve got a hundred people in the community, you’ve got a hundred different views. And that community would very quickly fracture and disperse. And the only way you can hold it in place and keep the community going as a community and therefore doing its job for us, is by being able to exercise self-restraint and so on and talk people around and use diplomatic ways of doing things to maintain the stability of the relationships among the individuals.

Jim: Yeah, very good point. Let’s move on to another topic. When I try to get my head around the body of science, one of the things I like to look for is conservation laws. And one that seemed to keep popping up throughout the book, or it’s not as rigorous as say the physical conservation of energy or something like that, is time. And that time seems to have a conservation law-like element in the domain of friends and friend-like relationships. Talk to us a little bit, you must have brought it up 20 different times in the book. It was a theme that was subtly woven throughout.

Robin: Time is the secret of the universe. Contrary to Douglas Adams’ 49 or whatever it was in the Hitchhiker’s Guide to the Galaxy, it’s actually time. Einstein was right all along. And that’s simply a consequence of the fact that these bonding mechanisms we use are very time dependent, and we have to keep repeating them in order to maintain the quality of any relationship we do. So in other words, to create a friendship, you have to invest a lot of time in it, at least at the beginning, to get it up and running as it were. And then once it’s up and running, you have to keep investing in order to maintain it. So friendships are very expensive. And indeed we devote something like 20% of our entire waking day to social activities. This is non-trivial stuff, we’re servicing our relationships and maintaining their quality so that they will be ready to function in the way we need them to function.

Robin: When we need help, the people that we’ve built these relationships with really will come to our aid. And one of my challenges, again, if you don’t believe me is just go out and try it. Go out into the street to the first stranger, when we’re allowed to do these things again, the first stranger on the street and throw your arms around him or her and say, “I need a hug, my life’s fallen apart, help me.” I’ll bet you anything you like that their response will be to get their phone out and call the ambulance or the police, one of the two. Whereas if you do that to your handful of shoulders to cry on friends, those four or five people that are very meaningful to you, of course they will immediately drop everything and do what’s required. And this really highlights the fact that it is no good going to somebody and asking for their support and so on after the event.

Robin: The best you’re going to do is them demand some payment for putting themselves out and so on. Of course, that’s why we pay doctors and psychiatrists under these circumstances. If you wanted instant support and help, you have to set these friendships up well ahead of need. If you’re very lucky, you may never need them. It’s like an insurance policy, it’s money well spent. And of course, at least with friendships, we get some fun on the way. But believe me, if the situation does arise and you really need that kind of emotional and social and maybe financial help, those friendships are a godsend, they’re what will keep you going as it were through the dark patches, out into the sunlight on the other side of the tunnel. And that’s very expensive to do.

Robin: Of that 20% of the day that we spend in social interaction, which is something in the order about three, three and a half hours a day, one way and another. That’s not to say conversations with people at work necessarily unless they happen to be friends of ours, or we’re having a casual chat with them. But 40% of that time is given to our five core shoulders to cry on friends. And we really heavily invest very, very heavily. And then we give another 20% of that three and a half hours to the next 10 people that make up what’s called a sympathy group layer of about 12 to 15 people that are very meaningful to us. So 60% of our total social effort and time and emotional capital is given to just 15 people, and the rest of the people in our extended social circle get on average about 30 seconds a day, I calculated it out. But they don’t need so much out there.

Jim: They get a little text message now.

Robin: [inaudible 00:37:03]. Just a reminder, “I’m still here.”

Jim: Exactly. One of the things I did find interesting, and again, when looking at science, where do you get information from, well these population numbers work for large populations, there’s considerable individual difference based on all kinds of things. And that actually provides an interesting clue. So for instance, you guys found that extroverts have more friends than introverts, but they spend less time per friend. Conservation law.

Robin: Absolutely so. Yes, these standard numbers we come up with, the five and the 15, the 150, what’s known as Dunbar’s number, are extremely constant. You see them in every data set you care to look at, almost no matter how it’s obtained. But built around that is a lot of individual variation. So let’s say Dunbar’s number of 150 people, which is your extended social network, the total list of all the people, family and friends, that are meaningful to you in terms of their relationship. So that can vary between maybe 100 and 250, depends on age, depends on sex, it depends on personality, all these things factor into it and create a lot of variability. And indeed, as you mentioned, extroverts tend to be at that top end of that, they’ll have maybe 200 to 250 people in their Dunbar circle whereas introverts will perhaps be down to a hundred. And we think the reason basically is that introverts are risk averse.

Robin: In other words, they would rather have fewer friends that they can give each of them more time to make sure that that friendship really works as a friendship. Whereas extroverts are trading on this social confidence to be able to ride out rejections. So if they go and beg her favor from Susan and Susan says, “No way, you never paid me back last time,” their response would be just to shrug their shoulders and go on to James and see what they get them to do. It’s just two equally good ways, really, of solving the same problem, how do you ensure you will always have people to support you? But it does mean that introverts’ friendships and family relationships tend to be warmer and more emotionally intense than those of extroverts, it seems. And we can pick these up even in things like the frequencies with which people telephone each other, as well as in their ratings of how emotionally close they feel to their individual friends and family.

Jim: Yeah. I liked the way you guys were able to use and marshal a lot of what we might call social physics type data. From lots of different modalities, phone call lengths, text message, patterning, et cetera. It’s interesting that we’re able to do that now.

Robin: It’s the last no more than 10 years, but really perhaps even only the last five years, the capacity to mind these kinds of data has proved to be enormously beneficial for our understanding of how things work. Because prior to that, we had to ask people to make lists. And when we first started doing this stuff only 15 years ago, we had to ask people to sit down with the very big sheet of paper and say, “Write out all the people you have meaningful relationships with, all 150 of them, or maybe 250 of them.” And we often ended up with not a few people being very, very cross. One of our researchers is reporting back that one of his aunties, I think it was, had completed one of these forms for us.

Robin: And when she sent it back, pinned to the top of it was a little note which said, “Do not ever ask me to do anything like this ever again,” because it probably took [inaudible 00:41:06] several evenings of her busy time to actually do it. So to all of them, we’re very grateful, but thankfully now we can collect data much more easily and faster through using telephone call databases or things like sometimes Facebook, there are publicly available Facebook datasets, which are old now, but were made available by Facebook a very long time ago. And again, with things like the telephone databases, we have no idea what’s being said in the phone calls, of course, because that’s not recorded or all we have is the bill listings, if you like, of who called who and for how long. And that’s as much as we know.

Robin: But out of that you can see very beautifully these very consistent patterns in terms of how frequently people contact each other and how many people are in their address book, if you like. And then what’s interesting out of that is that actually all these different ways of contacting people, whether it’s texting or phoning or Facebook or email or face-to-face, the frequencies with which people contact the individuals in their different social layers of their network of virtually identical. In other words, we use these new digital means of communication exactly in the same way as we use face-to-face contact. With the advantage that we can contact the person even when they’re not physically present.

Jim: It’s quite interesting. In fact, you’re one of the proponents of the social brain hypothesis. It again, may provide a unifying lens for why all these different modalities would show similar clustering patterns. And in fact, you referenced work and you did some of the work yourself, not only on humans, but on other social mammals. And they’ve been able to drive some similar dynamics, or we might even say regularities based on the attributes of the animals and how they interact and their brains. Tell us a little bit about the social brain hypothesis. This is really interesting stuff.

Robin: Yeah. So the social brain hypothesis actually originally came or was proposed as an explanation for why monkeys and apes have much bigger brains than any of the other species of animals that share the planet with us. And in terms of brain size for body weight, much bigger brains than even whales and elephants and all those large bodied animals with big brains have. But it out that in monkeys and apes, but not for any major group of birds or mammals, there’s a very nice relationship between the size of a species’ brain and the size of its social group. So species that live in big social groups have big brains. In particular, it’s the neocortex primarily, which is the wrinkly surface bit of our brain. It’s only a few millimeters deep in fact, it’s a huge sheet wrapped around this small inner core of old mammalian brain. The inner core does all the stuff that keeps body and soul together for you. The neocortex on the surface is where all the clever stuff gets done, and a large chunk of that is devoted to managing your relationships.

Robin: So it’s partly memory, but it’s also actually all the computation you have to do to figure out why Jemima behaved in this particular way. What were her intentions and what are the consequences of that? How should you respond and what are the implications for the way she’s behaved for the other members of her social network and the other members of your social network? So what makes the social world of monkeys and apes complicated is that they are in a much more complex social environment where they’re calculating the knock-on consequences for other members of the group of what you do with another person. So it’s the third party consequences that have to be figured out in order to keep the group bonded and together, rather than dispersing. So that was shown with comparative data. Beginning about 10 years ago, we started looking at individuals in brain scanning machines. And showed that this relationship, this social brain relationship applied even within species, between individuals.

Robin: So people who have small social circles, small number of friends, tend to have smaller chunks of the bits of the neocortex that are particularly important in managing relationships. And this is rather a large neural circuit, consists of two components. One is known as the mentalizing circuit because it’s involved in you imagining what somebody else is thinking. And the other is what’s known as the default mode neural network, which is largely concerned with managing your emotions and those kind of cues as it were. So it’s the way these are then put together that allow you to handle complex relationships with other individuals, that seems to underlie the social brain effect. Although originally it came out and just looking at the whole brain as a whole, in fact, it turns out to be underpinned by a very discrete component of the brain, but a component which is actually, particularly in our case, extremely large. It occupies a very big chunk of the total brain volume and especially in the neocortex.

Robin: So here, in fact, rather nicely built in there, is the fact that if you look at the nature of monkey and ape relationships, how they build their friendships, it’s based on what psychologists would call a dual process mechanism. So it has two components which work in tandem with each other, but are very different and are based in different parts of the brain. And one is a kind of raw feels, the emotional content of the relationship. And the other is the more conscious cognitive part of the relationship where you’re evaluating an individual as an individual and evaluating their behavior, whereas the emotional component is just the sense of warmth you have that you can’t often put in words, just feel attracted to and very warm towards this particular person. And these two components are there with us, and they perhaps reflect the difference between the mentalizing and default mode neural networks, and explain why the two appear to be important in this context.

Jim: Just wanted to clarify for the audience, when we’re talking about the mentalizing circuits and networks, another term that is often used for that kind of cognition is theory of mind. Are they pretty much similar concepts?

Robin: Yes. And a third term that often appears in this context is mind reading, which perhaps is easier to comprehend more straightforwardly. In other words, it’s your capacity to read somebody else’s mind. So theory of mind is the term invented by philosophers, who clearly always like to confuse everybody by using inscrutable technology. But the logic of it makes sense. In other words, it was that you had a theory of somebody else’s mind is what they had in mind when they called it theory of mind. So it’s the ability to understand what’s going on in somebody else’s mind. Actually, although that’s the major [inaudible 00:49:11] really which only we and maybe the great apes, the orangutans, chimpanzees, and gorillas, share, none of the other animals and birds seem to be able to do this kind of stuff. This theory of mine, reading one other person’s mind, is actually by our standards, very small bear, indeed.

Robin: And it’s a capacity that children develop at about the age of five and become pretty competent at it, as competent as adults, certainly by the time they’re six. But humans, as they develop from that age into adults, the capacity becomes larger and larger scale so that we can factor more and more minds in at the same time. And what normal adult humans seem to be able to do is to handle five people’s mind states at the same time. Now, of course, one of those is yours, right? So because you have to be imagining that somebody else is imagining something. But it means that you can handle four other people’s mind states simultaneously. That’s a hugely costly thing to do in terms of neural processing and computing capacity of the brain. But it also perhaps explains why conversations never get beyond four. So four seems to be the absolute upper limit of conversation size, is the number of people you can have in a conversation at any one time. If you get a fifth person in a conversation, it will break up very, very quickly into two conversations.

Robin: We seem unable to do more than that. And it’s a slight joke, really, if you like, rather than necessarily something [inaudible 00:50:57], but I have this vision that the reason it’s set at four is that when we’re having an interesting conversation, it’s always about somebody else who’s not there, and that’s the fifth mind that we’re speculating about. Just comes out very nicely if you look at a good dramatist or perhaps a good novelist, actually, but so we’ve done it with dramatists, we’ve done it in films, contemporary films, and we’ve done it in Shakespeare’s plays. They never have more than four people having a speaking part at any one time. So if you look at Shakespeare’s plays, it’s always only ever a maximum of four people because clearly sitting at the back of Shakespeare’s mind intuitively, it was just his skill as an observer of humans to appreciate this, is the audience has to contend with the mind states on the stage. And the audience is using up, or the audience member is using up, the first mind reading level, as it were, and-

Robin: The first mind reading level as it were, and they can manage five, so that just leaves four slots on the stage. Shakespeare’s absolutely rigorous about this, and in fact, if the characters on the stage are discussing somebody else’s mind state, who’s not on the stage, but somewhere else; they’re speculating on Ophelia’s mind state when she threw herself into the stream in Hamlet, or whatever it may be; Shakespeare reduces the number of people on the stage in the conversation to three.

Robin: He’s really clued in on this. It’s just amazing, but it’s a reflection of the fact that there are these natural limits and it’s a consequence of the fact that the computing power needed to… because what you’re doing actually is creating a virtual world in your own mind, a kind of model of the world out there. You’re modeling somebody else’s mind by creating avatars inside your own mind, and this is hugely computation expensive for the brain. Of course, it’s perfectly possible to have a brain that’s so enormous that we could sort of keep in our mind states of the entire population of the United States going simultaneously, but the brain size you’d have to have to do that would be the size of Jupiter probably.

Robin: So there are practical limitations and I hesitate to say this, but half the population may have something very definite to say about the size of babies heads when they’re giving birth, which is really what the limitation is. The ultimate constraint is, what, given our body sizes, we as a species can actually give birth to, and the limiting size of the baby at birth for all mammals is the size of the brain.

Jim: Yep. Size of the birth canal, the pelvis, and the brain, so clearly one of the serious constraints in evolution. Well it’s about that time. Let’s move on to that topic. If I’m going to talk to Robin Dunbar. I certainly got to talk about the Dunbar Number, so maybe he could tell us a little bit about the history of how you came to derive it.

Robin: Well, this was, as is often the case in science actually, a complete accident. A bit of serendipity here. I was trying to solve a very trivial problem to do with primate behavior. To do with grooming actually, and it occurred to me that the social brain hypothesis, although it was in a slightly different form, which had just been proposed at the time by somebody else, was this relationship between… The fact that primates have bigger brains than other species, is because they live in much more complex societies and they just need a bigger computer to handle all the information.

Robin: It occurred to me if that’s true, then it should be the case that species group sizes correlate with their brain sizes, so got the data out of the journals, and put them on a graph, and sure enough they did. This probably was sort of about three o’clock in the morning after several beers, struggling with all this stuff. I made the absurd, or had the absurd thought that, “Well where do humans fit into this?” Since we know how big the human brain is, let’s plug them into the regression equation for this graph and see where humans would lie.

Robin: What that predicted was a group size of about 150, and I have to say, I thought this was rather too small, probably by several orders of magnitude, given that we live in huge conurbations these days, but I thought, “Well, we’ve lived most of our evolutionary history in these very, very small scale hunter gatherer type societies, let’s see what size of communities these traditional scale, traditional societies live in.” One of the problems with that was not knowing really what the correct community type to choose in humans that would be equivalent to groups in monkeys and apes, because the problem with humans, but it turns out this is also true of monkeys and apes in fact, but humans very obviously live in sort of this highly layered form of social system, where you have small groups embedded within bigger groups, who are embedded within yet bigger groups.

Robin: Family is embedded in extended families who perhaps live together in a hunting camp perhaps, and then the members of the hunting camp gather together into community, and the communities gather together into a tribe, so you’ve got this sort of stacked hierarchical form of organization. What I actually did, was collect data on hunter-gatherer societies from around the world for all the data on sizes of the different grouping layers that they had and asked, “Well, do any of these correspond to this figure of 150?” It turned out to be community size. Community is the sort of… doesn’t really exist on the ground, it only exists in people’s minds, because what you see on the ground is these hunting camps, but if you look at which hunting camps meet up with witch hunting camps from time to time, and do each other favors, and all these kind of things, then out of that merge is a sense of the community. It’s this grouping, typically somewhere between about 100 and 200 people, so slotted very nicely around this figure of 150.

Robin: Later, what we’ve done is looked at people’s social networks to see how many people they know, and we’ve had to look at some other examples, like village sizes in medieval times in England. Some other people have looked at the size of essentially villages, grazing associations in the Alps. The Italian Alps, they’ve sort of… About eight centuries, I think, from about the 12 hundreds to the late 19th century, and you just see this number coming up all the time. It’s this sort of fundamental size, group size in the military, for example. It’s usually known as a company in most armies. You can see there, if you look up the army manual, American Army Manual, there it is, specified that it will be somewhere between probably about 150 and 180 people in size.

Robin: That’s the sort of platoons, the three or four platoons that’ll be involved plus the sort of ancillary offices, and what have you, and signals people that make up the company. That’s exactly the kind of size, and you see it around the world. British Army’s a bit smaller. We’re typically about 120, I think, in a company; the U.S., about 180; the Australians, about 150, so they’re all in this kind of ballpark again. We think that’s because that’s the limit on the size of group you can create a community out of. That’s why you have the sense of brotherly bondedness among the military. They work very hard at creating this sense of community at the level of the company. Anybody who’s been in the military will tell you the big needle matches in sports are not between the different regiments, they’re between the companies of the same regiment. That’s that sense of intense kind of brotherhood that military training really works very hard to create.

Robin: This is a very distinct kind of grouping and it corresponds exactly, really, to the size of the number of people that you have in your social network, that you have meaningful relationships with, and it got so christened as Dunbar’s Number on Facebook, I believe. I’ve never seen the original, but I’ve had several people say that that was true, but it’s since been adopted as the term for it. But technically speaking, it’s actually Dunbar’s Numbers. It should be, because of course this 150 is simply one in several stacked layers that all of these kind of groupings demonstrate very nicely. If you think of, again, the army, you’ve got sections within platoons, platoons within companies, they’re very similar to the layers you have in your social network.

Robin: You’ve got your shoulders to cry on friends at about four or five, which of course, is your tent group in the military, within the section. You’ve got your four man tent cooking, and eating, and sleeping together there at the base, and your shoulders to ground friends are set within a sympathy group of about 12 to 15, who are set within a social group of about 50, who in turn are set within your total social network of 150. Beyond that, there are several more layers, so the next one out.

Jim: Yeah. We’ll just dig into this. Of all the things in the book, this was, for me, the biggest eye-opener. I heard Dunbar Number and read about things like Hutterites. That’s actually came up in a conversation yesterday, Hutterites and Dunbar’s Number, and Christmas cards list and such, but this idea of concentric circles at a scale of three was kind of new to me. I really liked that part of the book, and it really produced a lot of thoughts. For instance, in the military, and the U.S. military, they actually do have a unit of about four called the fire team, which is half of a squad.

Robin: Absolutely. Yeah. Of course, that number four or four to five is your classic Special Forces Unit, your SEALs.

Jim: Exactly. Four is the seal team, right?

Robin: That’s right.

Jim: Two twos. They used buddies and then they produced two sets of buddies. You do not want to run into four goddam SEALS, I can tell you that. Not unless you got a flame thrower and a tank, very probably. Even then you’ll probably lose.

Robin: Exactly. Yes, and it’s exactly the same number in the SAS, the British equivalent, the Special Air Service. Four is the fire team as they were. This kind of makes sense, because these guys do most of what they do on their own behind enemy lines. So the last thing you want out there is members of a fire team who are just going to say, “Hang on a minute, I’m off for a coffee,” right in the middle of some crisis. You got to stick to each other’s butts like glue, and the only way you’ll do that is if you kind of literally live and die, day-by-day in your training together, and build up such an intense friendship that you have these kind of shoulders to cry on friendships, as we would recognize them in civilian life.

Robin: That in turn, limits the size of what’s possible for those kinds of groupings to about four or five. You simply couldn’t have more people and have the same kind of intensity where guys will just literally do a Custer’s Last Stand together as it were. Come what may.

Jim: Those guys will definitely do that. The other thing you pointed out, and I think it’s very, very interesting is essentially all the teams sports vary in size between five and 15. I can’t think of any sport, maybe Afghany Polo or something, where they use a dead goat instead of a ball. I think that’s a little bit bigger, but most of the sports that we know of are between five and 15.

Robin: Well, most of the team sports are actually between 11 and about 15.

Jim: I think basketball is the big anomaly there. I mean, that’s a very, very exciting sport at five

Robin: That’s dictated by the size of the court, as much as anything else and the size of the goal. You have to adjust those accordingly, if you like, but it’s certainly, football, soccer, hockey, field hockey, ice hockey.

Jim: Yeah, lacrosse, rugby, go down the list, baseball.

Robin: They’re all up at that 15. What’s interesting about most of those, is they subdivide the 12 to 15 into two parts, so you actually have two separate games going on. You’ve got the forwards and you’ve got the backs, operating basically, two kinds of games on the field. That’s a reflection, I think, of the fact that in order for these team games to work, you really have to be able to think your way into the mind of your co-players, as it were. You have to know that when Jim is going to lob the ball, without even having to look at him, you know when he’s going to do it and you know exactly where he’s going to put it, because you understand how his mind ticks so well, so that you’re there to receive the pass when it comes.

Robin: There’s a limit on the number of people you can really have that kind of deep mind reading sense with. You couldn’t do it with 50. You have to subdivide the 15 into at least two separate groups, the forwards and the backs, and they basically play completely separate games with the other half of the opposing team.

Robin: The interesting one actually is, of course, we have five a side soccer. Again, that’s played on a small court usually, but there is an entire league, it started in Denmark, I think originally, of three team soccer, so you have three teams on the field, but they-

Jim: That sounds pretty nutty. How the hell do you do that? Do you have three goals?

Robin: You have three goals, you have a hexagonal shaped pitch.

Jim: That would be kind of interesting.

Robin: The way you win, the winner is the people who have the fewest goals scored against them. Not the people who score the best goals.

Jim: I think that’s quite interesting.

Robin: You have three quarters, if you like, in terms of playing time. The game is divided into three sections, time sections, but they discovered when they did this, that five was really the limit. If you had fewer than five in each team, people ended up kind of having to run about too much, and if you had many more than five, so they tried it with eight and 15, I think. No eight and 10 at one stage, when they were developing this; everybody gets in everybody’s way, because there’s just too many people on the pitch, so they’ve sort of evolved this natural thing of three teams of five. It’s quite fun to watch. It’s quite interesting, because they get a lot of strategy going on.

Jim: There’s some game theory dynamics going on too, right? Two against one, right? It’s going to be a rotating series of two against one.

Robin: Exactly.

Jim: That’s interesting. The Americans have, in Texas in particular, they have a seven man American Football game that’s played by the smaller, rural high schools that couldn’t efficiently field the full 11 person team. That’s also a good game. It seems like you can have good games in a little bit broader range, but let’s go back to friendship now. Let’s talk about these, I kind of thought about them in a Tolkien-ish fashion, the rings of Dunbar that kind of start out… we’ll talk about 1.5 later, but let’s start back in the context of friendship, five, 15, 50, 150. You call them the support group at five, the sympathy group at 15. What do we think about the 50 and the 150?

Robin: Well, the 50, we sometimes call the affinity group, because I tend to think of these… and of course, the 150 is essentially your entire social network. All the people you currently feel you have meaningful relationships with. I tend to think of these, I’m taking a leaf out of your party animal youth here, tend to think of these in terms of what you do with them, and your inner core of five, or really, as I’ve said already, your support group, they provide you with emotional support and so on, but they’re your intimate, or more intimate social partners.

Robin: If you’re going to have a very kind of intimate dinner, maybe you would have your support group there as the dinner, but the 15 is probably your core general social group. If you were going to make up a party to go to the theater, or you just wanted somebody to go out for a walk through the mountains, and it doesn’t kind of matter too much who it is, you would kind of see who in that extended group of 15, because quite a few of these are going to be children making up the slots and they’re sort of tagging along with their parents. It’s the parents, that are the core members of your friendship group that you’re going for, but that 15 group is your sort of regular social partners.

Robin: Your 50 group is what I call your yard barbecue party group, so if you decide to have a bit of a bash one weekend in the year for your birthday, and you do a big barbecue in the garden, or wherever, it would be that group, you tend to go for. They’re your sort of party friends, I guess, you might call them. Then finally, your 150 is what I call your bar mitzvah, weddings, and funeral groups. These are the ones that will turn up for the one in a lifetime big events. I mean, you may not know much about them when they turn up to your funeral, but they will turn up. That’s a mark of their esteem of you.

Jim: That’s interesting. Yeah. As I think back, the parties, a good party, typically 40, 50, 60 people, in that range.

Robin: That’s right.

Jim: It’s interesting. I think the other interesting one, at least for Americans to think about, it’s 150, it’s kind of like your Christmas card list.

Robin: Yeah. Yes. This is an alien concept, we discovered, to Americans on the whole Christmas cards, but it was something-

Jim: Really now?

Robin: Really now.

Jim: A lot of them do it. We used to, but my daughter, amazingly enough, still has it.

Robin: Oh, my goodness.

Jim: My mother was as assiduous Christmas card person, and thinking through her list, it was a big thing she did all fall. “All right, who do I scratch off the list? Who has pissed me off? Who do I add?” Right?

Robin: Yeah.

Jim: It’s quite funny, and she’s even ask our opinion, “Should I scratch blah, blah?” I’d go, “Yes. She’s an annoying bitch.”

Robin: The Smiths never sent us one last year, we’ll not send one to them this year.

Jim: Exactly. You Brits are big on your Christmas card list, are you?

Robin: We certainly were, and I think this was sort of… certainly Northern Europeans, probably. This is quite a… well, a big deal, and most people send Christmas cards. Obviously, it’s kind of a 19th century phenomenon, I guess, but as you say, I mean, people invested a lot of effort in deciding who to send cards to this year. Indeed, they were going to spend a lot of money, because the cards are expensive. Well, they cost money.

Jim: And postage, yeah.

Robin: Postage costs even more these days. It was a big deal to decide who you’re actually going to include, and we used it originally in one of our very, very first studies, because we were kind of wondering, well, how do we identify the people that are kind of meaningful to you? With the relationships that you have that are sufficiently meaningful, that you will go out of your way for them. We hit upon the idea of Christmas cards as a way of doing it. This was probably about 15 years ago, we did this study, and at that time, people were still very active sending Christmas cards. I’m afraid, Christmas cards are dying out as fast here as they are in America. I don’t think we could actually do that study again. We wouldn’t get a big enough sample list probably, but fortunately now, we’ve got text messaging and phone calling databases that we can use instead.

Jim: Cool. Now, we’ve talked about out to 150. Let’s talk about the one that was most new to me, and kind of curious; the ring of 1.5. Now, how do you have… I know you have an answer of this, but I’m going to ask this question rhetorically. How do you have 1.5 friends?

Robin: Well, this goes back to… Whenever I was giving lectures about this, whether they were to university departments, or to the lay public, as they were, at science festivals, and I would point to these circles and say, “Look, here they go, 5, 15, 50, 150, beyond that it’s 500, 1500, which turns out to be the typical size of tribes in smaller scale societies. Indeed, now, it is another layer out at 5,000, which is the number of faces you can recognize as having seen before, so there’s the difference between strangers and non strangers.

Robin: Each layer is three times the size of the one inside it, so if you project backwards, and we start at five, but actually if you project the scaling ratio backwards, there’s a layer missing, and that layer’s at one and a half, and everybody would sort of sit bolt upright and say, “What do you mean?” Do exactly what you did. “How can you have one and a half relationships?” I used to say, I was kind of joking actually. “Well, of course, it’s the difference between men and women. That’s why it’s one and a half, because the girls can have two intimate friends, a romantic partner and a best friend forever. It’s a well-known phenomenon that girls have a very close intimate, usually, but not always, same-sex, platonic friendship. Us poor blokes can only manage one at a time, so we either have a romantic bond, or a best mate that we perhaps go drinking with, but we never manage to have two together at the same time. The average across the two sexes, that’s why it’s one and a half.

Robin: I didn’t really believe this, but some Italian colleagues of mine I was collaborating with, collated or analyzed this big Facebook dataset, and also Twitter dataset that they’d obtained, and blow me down, there, right at the center of this was this little layer of one and a half. I practically fell off my bar stool when they showed me these data, but it’s so robust. Every single dataset we’ve looked at ever since, there it is, and it’s basically, it is your intimate friendships, if you like, your intimate relationships. It probably is a consequence of the fact that by and large men only have one intimate relationship at a time, whereas women have two, one of which is platonic and the other, which is a more conventional romantic one.

Jim: Very, very interesting. Now, as a complexity science guy and a dynamic systems guy, when I see something like a scaling law of three, I want to know where does that come from? I know that’s a really hard question, and I know you guys have done some agent-based modeling, done some mathematical modeling. What are your senses of what are the constraints, and structures, and attributes that would produce an emergent result, and that’s what you’d have to call that, of scaling law of three? Why would that be?

Robin: Believe me, this is still something of a mystery. Probably the best suggestion we’ve had, which actually came from the social psychologist is that it’s a naturally balanced… Triads are a naturally balanced social grouping, because you will end up, if you like, with a range of opinions going on in there, and perhaps somebody will cite it, somebody else [inaudible 01:16:04] course, but it’s a kind of dynamic balance in there, in which the triadic relationship between them is held in tight sort of balance over time. In other words, it sticks together, but we don’t really, I don’t think, have anything like a remotely sensible explanation as to why it should be three.

Jim: I might see if I can get some of my friends at the Santa Fe Institute to think about this question. This is just the kind of thing they’re good at.

Robin: That would be absolutely great. I must say, unfortunately, when I was at the Santa Fe Institute, visiting some while back for a week or two, this never came up, because we didn’t really appreciate, back then, what the problem was, but several groups of physicists have had a very good go at trying to explain this. We can explain it to some extent in terms of the trade-offs between investment patterns, but I think at the end of the day, what it probably comes down to is the fact that the core basis of our sociality consists of really rather small groupings. These groups of five and maybe 15.

Robin: The groups of five are very much interlinked with each other, but your grouping of 15, your sympathy group, consists of your five and two other people’s fives as it were, so you’ve got three little clusters of five linked together. This pattern of replicating that process creates these layers. We see exactly the same thing in primate social groups, so it looks like being a pretty universal thing, but even so it’s still not obvious why it should be a scaling ratio of three rather than two. It is two in some cases in primates, in the less socially complex primates, the scaling ratio is two. That’s easy to explain, because it’s simply a consequence of groups splitting when they-

Robin: … is it simply a consequence of groups splitting when they hit their upper limit, but then, rather than moving off, they’re somehow held together by weak bonds. I’m always reminded here of deep physics, as they say with weakened strong forces bonding groups. We’ve got the…

Jim: The three quarks or whatever.

Robin: That’s right. The sort of inner core of five being held together with very strong bonds, strong forces, and then weak forces holding the other little similar groupings together. And it’s creating this sort of ripple effect getting out. So everything’s done in multiples of three, but as I say in less intensely social primates, it does seem to be too. And that can just be explained by natural efficient processes. When a group gets too big, it splits into two and that’s a natural division for the way things work in the biological world it seems, but why it should be three then in these complex species is a mystery.

Robin: Why three, rather than four, and what’s wrong with five because at the end of the day, these groupings exist to provide protection and defense for the members of the groups primarily against predators. So, this is exactly the same problem the armies have on the battlefield, the group with the biggest, the biggest army wins. So if you want to kind of overwhelm the predators out there, then the more of you there are in the group, the less likely they are to attack you. And so there’s this pressure to increase group size.

Jim: Must be some costs to that, probably a balance between benefits and costs, right? We often see that in evolutionary dynamic.

Robin: The costs are absolutely massive. And the costs come in various forms. Part of which is the fact that the more of you there are the further you have to travel each day for everybody to get their sort of square yardage of foraging ground because you can’t all sit in the same pear tree and eat the pears. You all each have to have your own pear tree. So that means you have to travel further. That means you have to eat more food. But in addition to that, the stressors and these seem to be the really crucial ones, the stresses of living together in close proximity, don’t we know it, you say, that actually they have terrible consequences in terms of de-stabilizing the female menstrual cycle.

Robin: So if you have two new, and this is a mammal wide problem, and it explains why mammals in general only live in very small groups, that if you have more than about five females together in the same group, the stresses of having so many people in close physical proximity, so many animals in terms of physical proximity results in all the females being functionally infertile, and the group will go extinct because you’re not producing any babies. And the species like primates and a few others horses, elephants dolphins, for example, in order to live in these very big groups have had to solve the problem of how to keep a lid on that, those stresses.

Robin: And they’ve done it essentially by forming coalitions. And those coalitions then form these inner inner cores because we see exactly the same layered structure in their groupings as well, but there’s something odd about these numbers, five, 15 and 50 and 150, which seem to make them what in networks answer or graph theory would be called attractors. There’s something very stable about those numbers. Anything in between tends to sort of be unstable and fall apart. And because if you look at the distribution of group sizes in primates, those are the predominant numbers. They either tend to live in groups of five or 15 or 50. And if you look at the groups of 50 or our own groups, 150, then what you can see inside the group in the way the relationships between individuals are is those other numbers. Your group of 50 is subdivided into a group of 15, which is subdivided into a group of five. Exactly as you see in the structure of your social network. Exactly as you see in the US army or anybody else’s out there, if it comes to that.

Jim: Very interesting. Oh, well, it’s certainly a topic for more thought. Well, we’re getting kind of late in time, we’ve got so many interesting topics. I’m going to do a little triage here. Let’s talk about two more topics. One are your seven pillars of friendship and then how friendships and how about that.

Robin: That sounds good.

Jim: Then we could end on endings. So let’s start with the seven pillars of friendship and homophily.

Robin: So yes, I mean, it’s been known for a while that one of the defining features of friendships as it were, what characterize those friendships is that people tend to be very similar to each other in many of their kind of interests and cultural traits as it were, but it turns out to be a massively strong effect. So if you look at people in your friends and indeed even your family members in your various layers of your networks, you will share much, much more in common with the people in the inner core than with the people in the outer core. And of course you will share much, much more in common with the people in the outer layers of your network then those people outside your network that you aren’t particularly friendly with just acquaintances, or maybe even just random strangers.

Robin: Now the seven pillars of friendship are really a set of dimensions, cultural dimensions, rather like a supermarket barcode on your forehead if you like, which identify in effect the community you come from. So they kind of specify your likes and dislikes and beliefs and interests and so on, and where you come from. And what we seem to do is to sort of wander around the world, checking out people’s seven pillars to see looking for the ones who match ours most closely. Now these seven pillars are all cultural, so they vary through your lifetime to some extent, but they kind of defined in many ways by the community you grew up in. So I think what they are is the set of common beliefs and the like that define the community. You are socialized in the community where you learn what it is to be human, if you will. And they are essentially having the same language or better still dialect in the case of very big language groups, and dialects are extremely localized in these big languages, in English, English English for example.

Robin: It’s been known for a long time that you can place a native English speaker within about 20 miles of their birthplace by their dialect. The moment they open their mouth, you know exactly where they come from if you know English dialects. Now I think this is generically true around the world and certainly other people in sort of Germany and France have said, you can probably do the same there too, but I mean, dialects are extremely localized. What it is of course it’s about being able to have a conversation with them, but also the way they use the words, the way you use the word, and it means it’s much easier to have a conversation because you kind of don’t have to explain the joke and all these kind of difficulties that get in the way of the flow of a conversation.

Robin: So it’s having the same language, it’s coming from the same area. I think is growing up in the same area. In other words, you know the same streets, you know, the same bars, you know the same cafes, even if you weren’t there at the same time, having the same educational trajectory. And I think this is a lot to do with your knowledge and the things that interest you as it were is why clearly doctors have mostly friends as doctors, lawyers only have lawyers as friends.

Jim: Yeah. In my family, it’s cops, right? Got a lot of cops in the family. And I’ll tell you what cops have a more inbred social life than Supreme court justices.

Robin: And again, what it’s all about is knowing the same kinds of things to talk about. It’s having the same interests. And there’s having the same hobbies and interests, having the same worldview, which is really a composition of your moral, political, and religious views, liking the same music. In other words, having the same musical tastes and having the same sense of humor. Those are the two that are always very surprising, but it turns out the best predictor of whether a stranger would make a good friend is actually whether you share the same musical taste with them.

Jim: That is interesting. That is so very interesting. Now, one of the things that when I was reading this list, one of the things that it struck me as is it kind of confirmed one of my own thoughts, which is our society today has this obsession with diversity, right? And people speak of diversity as if it’s a monotonically increasing good, more is always better. And I’ve tried to point out to people that diversity definitely has benefits. There’s a lot of good that comes from diversity, but there’s also costs. And if we think about your seven pillars and we compare it with say very much increased cosmopolitanism, particularly in the big mega cities, as we’re talking about, it would seem to me that high levels of diversity would seem to indicate making friendships would be more difficult.

Robin: Yeah, it is beyond friendships really, because what we’ve been able to show is that the more of these seven pillars you share in common, of course, each pillar can be kind of subdivided in fine detail if you want. The more of the seven pillars you share with somebody, the stronger the friendship is likely to be. So literally, the number of pillars you share declines as you go through your own network. And this is true of family, friendship, relationships, as it is of true friendship. And initially, you trust the people more, so those you share more pillars with. And I think that’s what they’re actually all about. They do identify a very small community, essentially the community you grew up in which in kind of historical terms is your little local hunter together community, always living in the same territory whom you see on a regular basis. You know how they think, you know how much you can trust them. It might be, you can’t trust them at all, but at least you know that for a fact.

Jim: At least you know, right.

Robin: But in general, they think like you, they see the world like you, and therefore, you can make assumptions about how trustworthy they are in terms of your daily interactions or negotiations with them. And that’s what the origins of the seven pillars are. They’re very flexible. And in some sense, that’s the whole point. It’s like dialects is this precise example of this. Dialects change with an unbelievable speed, generation by generation. So the kids in some obscure part of the Smoky Mountains do not talk exactly like the adults do. And the adults, the parent generation do not talk exactly like the grandparents. You’ve got this generational shift in dialects, which of course eventually, after a thousand years or so, may give rise to a completely new language.

Robin: But that generational shift allows you to identify a specific cohort in a specific community as being effectively your peer group. They’re the ones that you can gravitate to, build these kind of coalition-y friendships of mutual support, and it’s very difficult then for incomers to kind of cheat on the system then because they can’t come in and pretend to be a member of your community that you’ve just not happened to have met before, because you can tell absolutely instantly, you just don’t know the things I know, and you don’t speak the way I speak. So this seems to really strongly underpin our friendships for better or for worse. But I think you’re right that one has to think very carefully in terms of how we manage diversity, because there are clearly benefits in terms of business, if nowhere else, design of products.

Jim: Oh food, God damn it. If you had to eat British food all the time, God, wouldn’t life suck, right? Aren’t you glad you have Indians and Ethiopians and the Afro Caribbeans, otherwise you’d be eating bangers and mash and steak and kidney pie every day.

Robin: Exactly so. comfort food we refer to it as.

Jim: Well, I actually like steak and kidney pie. I like to hit the pub, an old style pub with the boys with the cloth hats and get me a steak and kidney pie. But every day, I’m not so sure.

Robin: At the same time, in terms of how well a group gets on, then the more they have in common, the more efficiently they will actually work together. So this is a trade-off here, the genuine trade-off that one has to kind of balance very, very carefully because there’s no optimal solution. In principle, more diversity is a good thing of course, but also more closely bonded to things.

Jim: Exactly. Yeah. So we got to think about, it’s a question of balance, like so many things, right. And trying to attempt to turn diversity into a monotonically increasing good, it just strikes me as who came up with that. It makes no fucking sense. Right. And yet we hear it a lot, particularly in pop culture. It’s always, we consider the benefits from diversity and the benefits from homophily or similarity.

Robin: This is possibly because the context in which that kind of appeared is the context of why their community integration, communal integration at the kind of global level. And clearly that’s a problem. If you have too much echo chambering going on and siloing going on, you’ve got communities where you don’t integrate well enough and you don’t benefit from culturally what they have to offer, and therefore multiculturalism and diversity is a good thing in that it may increase your levels of communal cohesion if you like. But there are contexts in which applying that willy-nilly to everything simply isn’t going to work because of the task demands that are actually involved. It may be counterproductive on certain scales in certain contexts. I think that’s really the message isn’t it.

Jim: Yeah. And that makes well worth people thinking about. Well, let’s go to our last topic and then we’ll end with the end. You have a whole chapter on how friendships and also romantic relationships and other such things end. What can you tell us about that?

Robin: Well, I think the short answer is friendships have a natural cycle anyway. They don’t last forever. So people kind of very often sort of concerned at the moment that when they emerged from lockdown, their friendships will have changed and they will be losing friends and so on. And my answer to that is no, that’s just part of the natural cycle. That happens anyway. And at certain ages, it’s very, very fast. Our datasets are on kind of the late teens, 20 somethings suggest that something in the order of a third of all friendships change every year, at least they change layer, which means they’re changing emotional position if you like. And if you don’t see people for a while, the quality of that friendship will decay to the point where they cease to be counted as a member of your 150.

Robin: I mean, they just get pushed out into the acquaintance layer beyond, somebody I once knew, but I haven’t seen for ages, really don’t know much about what they’re up to these days. Turnover is going on all the time. It’s a bit slower once you’re into mid life, thirties, forties, fifties. Seems to increase a bit more as you get older, as people leave and move away and when they retire and so on and perhaps die as well, but still even in midlife, I mean, there’s a constant turnover going on. Friendships probably don’t last more than about 10 years, except in a few rare cases. So if you look back on all the people you were at high school with, you may have kept up with one, maybe two particularly strong friendships, which have kept sort of survived the test of time, if you like, but the rest of them, if you ever get to meet up, when you’re 40 or 50 at a school reunion, it’s kind of entertaining for half an hour, but at the end of it you kind of think, dear God, was I friends with these people? Who are they?

Robin: So this is a natural part of the cycle of social relationships, I think of all kinds. But of course there’s a difference between those which drift apart, which kind of is what tends to happen with generic friends. So somebody kind of annoys you just a bit too much. You just don’t see them. And the friendship then just dies very, very quietly and slowly disappears. The interesting ones, of course, there’s the catastrophic failures, which are very difficult to repair. You often only repair it with deathbed reconciliations because the intensity of the breakup is so great and they tend to be confined to very close relationships, so parents, siblings, romantic partners, obviously, your kind of very much your best friend, the best friend forever in that sort of sense.

Robin: And they tend to be the result of catastrophic misbehavior at some point. In other words, well, let’s put it this way. I think with those very close relationships because they matter to you, you tend to be much more tolerant of them and give them more leeway. And also that makes the other person become more casual, a little bit more casual and just kind of assume that everything’s fine. And so you have constant little sort of irritations that go on that get overlooked and forgiven and so on, but eventually it’s a straw on the camel’s back phenomenon. So the final straw may be quite trivial, but it’s the 20th time they’ve stood you up in the last couple of years, or they borrowed money and not paid back. And you kind of just draw the line and say, that’s it. And that kind of breach, it’s a breach of trust is what seems to happen in these cases.

Robin: And you’ve invested so much in those relationships. You feel so let down that you’re deeply upset about it. And it’s that level of upset then that tends to create this really complete rift. But what is surprising to us is when we carried out a survey to see how common different kinds of breakups were and what were the causes is how many people fell out with their parents or alternatively parents falling out with their children. But really that relationship which you imagine ought to last a lifetime and beyond even, and yet it seemed astonishingly common. About 20% of all major breakups, something of that order were between parents and offspring. And those are often almost irreconcilable. The hurt and the trauma are so great from the breakup that it’s extremely difficult to sort of get back together and forgive if you like.

Robin: In a way you might do with a casual friend, oh, right, I forgive you, but I’m not seeing you again. That’s that. But to do that with close family members, siblings, or parents seems very counterproductive because they’re the one group of people who, when everything else has fallen apart and everybody else has abandoned you, they’re the one group of people who will stick by you and come to your aid and this is a considerable costs that some people appear to be paying for whatever benefits they think they’re getting out of improving their social relationships, social networks in other ways, maybe.

Jim: Yeah. The old saying, what’s the definition of family, the people who have to take you in.

Robin: Exactly so.

Jim: And if you break those up and you’re really stuck and you’re right it’s a surprising amount of that. And you mentioned something in the book, which something I’ve seen before with a scary amount of frequency, is how siblings can fall out permanently and irretrievably at the time of the death of the parent, maybe the last parent particularly.

Robin: Yes. I think this is a consequence. I mean, that’s a consequence clearly of the stress of the circumstance, and often there are kind of arguments about inheritances and details, and who’s been doing all the work looking after the parents in their old age and how are we going to do the service, the burial service, and what have you, can cause lots of disagreements that become quite fatal in that sense. But I also think it’s partly a reflection of the fact that our ability to manage relationships is really very, very, very small scale so that while the parents are present, they connect both as the kind of policemen, if you like, of the family social environment, but also the sense of obligation you have to them means, and it goes back to this mentalizing business and being able to handle many different mind states at once that you don’t want to fall out with your siblings because your parent is part of that triangle.

Robin: And if you can have an argument with your sibling, it’s tantamount also to having an argument with a parent. And so you kind of keep a lid on it, but when the parent’s no longer there to provide that sense of obligation, then the relationship can fracture because the problem for you at that point, if you like, is that you also now have another new network that’s been growing over the years to deal with, and that’s offspring, right, your own family. So, what was once a parent and some siblings, clearly now consists of a parent or parents, some siblings and the siblings’ own offspring and the siblings that turning their attention from upwards, if you like, towards the parents and sort of the family they were born into to the family they’re creating. And that becomes sort of a bit tricky to handle several sets of these simultaneously when they’re all so close and intense.

Robin: And so we have this kind of psychological limitation on the number of relationships we can, close relationships, we can manage and keep sort of functioning together. And of course, you’ve got this problem of scale all the time is the bigger that a family, extended family unit gets, the more different opinions you can have and therefore the more arguments you’re going to end up with. So there’s sort of everything is sort of conspiring against us in this respect. I think that may explain why you when you get the added stress of a death and the funeral arrangements, and it’s sort of what to do with the inheritances and all that kind of thing, it’s very easy for the thing to boil over and explode and fractionate completely and become irreparably so, which of course is a great, great pity, but it does, as you say, seem to happen surprisingly often.

Jim: Well, on that somewhat dire note, we will have to end it here. We’re already all past our normal time, but this conversation was so interesting. And as I mentioned, I did leave out some of the more interesting stuff, sex differences between friendship networks, romantic relationships, and some other very cool things. So if you want to learn more read Friends by Robin Dunbar and thank you Robin for just a most interesting conversation.

Robin: Thank you very much. It’s been great fun actually.

Production services and audio editing by Jared Janes Consulting, Music by Tom Muller at