Lydia Denworth

The Science and Necessity of Friendship

Air Date: February 3, 2020

Science journalist Lydia Denworth discusses groundbreaking research on the evolution, biology, and power of friendship.


HEFFNER: I’m Alexander Heffner, your host on The Open Mind. My guest today explores the science of how we think, learn and connect, including the interactions between our biology, our brains and our behavior. How do our perception stimulate social dynamics and decision-making? Lydia Denworth is the author of two books of popular science “Toxic Truth: A Scientist, a Doctor, and the Battle Over Lead “and “I Can Hear You Whisper: An Intimate Journey Through the Science of Sound and Language” and now she adds a third to her repertoire, which we’re here to discuss. “Friendship: The Evolution, Biology and Extraordinary Power of Life’s Fundamental Bond.” Denworth is also contributing editor at Scientific American and writes the Brainwaves Blog for Psychology Today. Thank you for joining me, Lydia.

DENWORTH: It’s lovely to be here.

HEFFNER: I think this is really an appropriate and important topic, not just because you uncover the lost and unsung science of friendship, but because we need more friends in our lives today in this digital environment.

DENWORTH: We do. As a science writer I mostly cover the brain. And so I was interested in how, well what neuroscience is mainly interested in these days is mapping connections in the brain, inside the brain, but I went to a meeting about social neuroscience, which is a sort of newer field within neuroscience and that is about mapping connections kind of in and outside of the brain, this kind of web of, of connections that we have with other people. And I sat there at this meeting listening to them talking about all these elements of social behavior and what it does in the brain. I thought I was right at that moment sort of wedged in between a parent with Alzheimer’s disease and teenagers. And so I was very buffeted day in day out by other people’s emotions and ups and downs and, and so it made me think about the ways that people in our lives affect us, even our biology, the way they make your pulse pound and your adrenaline spike. But then I also thought about here I am losing my parents and my kids are growing up and out and I better make sure I’ve got my friends. And that’s one of the big topics that social neuroscience gets into. So that’s really how I came to it. Just, you know, it was that kind of confluence of my personal life and the, the work I was already doing. But then the more I dug into it, the more, the reason in that whole field of social behavior that I really chose to focus in on friendship is because it has just not gotten the respect it deserves, right? And I feel like the importance of it has been, it’s been sort of hiding in plain sight, friendship. And we all think we know what it is. It’s so familiar in a way that we, and we think we think it’s important, but we don’t actually act like it a lot of the time in the fundamental ways that really matter. And I wanted to understand that. And then I discovered that in the last say 20 years science has gotten quite serious about friendship and about social relationships. And I wanted to explore how that has evolved and why.

HEFFNER: So you are giving rebirth this science in the book and you’re acknowledging that friendship revitalizes us,


HEFFNER: That is one of the core theses here. How does that work scientifically?

DENWORTH: I think the most interesting part of the science or the newest part of the science is the biology is one part of it, is this question of how is it that a social relationship, which is not like food that you actually put in your body or exercise where you’re moving your muscles and you can understand why going for a run might affect your blood pressure.

But why is it that a conversation with a good friend sort of gets inside your body and changes the way your body works? I mean it literally affects your blood pressure, your sleep, your stress responses, your immune system, all of those things. And so that to me is fascinating. That’s not really something, we understood because there’s that sort of

HEFFNER: Well, it’s the chemistry within the biology.

DENWORTH: It’s the chemistry within the biolo… I mean it’s, it’s a lot of things and there’s still a lot we don’t know about why exactly it does what it does, but when, you know, friendship for a long time was not studied seriously by biologists anyway because it’s very hard to measure. It’s hard to define. And science is all about measurement and definition. You know, you need to know what it is you’re trying to measure in order to sort of make a statement about it.

And, so you know, that there’s, so there’s a biology, but then also the evolutionary side of it is fascinating as a science because it’s really saying that we humans share a drive to connect with a lot of other species. And once you understand it that way, you have to understand that while friendship in human society has a lot of cultural aspects to it, and it’s not entirely cultural and that’s the way people imagined it for a long time. I mean, C.C. Lewis, the famous writer, he said, you know, friendship has no survival value, but it gives value to survival. Well it does give value to survival, but actually it literally has survival value. And so, you know, in people, but also in other species, those with the strongest social bonds live longest, have the most reproductive success, which is the evolutionary measure, you know, that you want. So that science of understanding that is what has sort of broken wide open in the last few decades and really fascinated me.

HEFFNER: It’s the way that we respond: we might text one friend because we know that they’ll make us laugh in a certain way. In that sense, it’s very; it’s an accessible science, right?

DENWORTH: It is an, yes. I mean, and, and it’s something everybody’s interested in everybody, you know both the people who have both think they have a lot of friends and people who say, ah, I don’t think I need friends. You know, everybody has a view on this. And so yes, it’s accessible in that way. It’s the, it’s, what I’m hoping to do here is like peel the onion a little bit and really explain to people that, why this is so important and why those headlines you’ve seen about loneliness and why, you know, there is a growing sense in society that, that relationships are important. But you know, not very many people really get the deep story of why.

HEFFNER: And not instant message or text relationships, so, you know, that’s one thing that really struck me about the book and the subject because we are in this climate of increasing domestic terrorism, and of course lone wolf attacks where there are stories after stories of assassins who have massacred people because they were not, they didn’t have friends. I mean, they were loners or they were losers to quote Bill Maher recently, right, and so we need to understand the science of how we can relate socially to rebuild capital, social capital.

DENWORTH: Social capital. Yeah. It’s, I mean, it is so distressing to see these people who are so unconnected and you know, or then they think they’re connecting online in this kind of, you know, with people who think like they do. But that is so different from what real true friendship is, you know, and people worry and I worry that the word friend has been, is devalued currency these days with social media.


DENWORTH: But I’ve actually come to feel it’s not,

HEFFNER: Revalued,

DENWORTH: It’s revalued. It’s valued anew, it means different things. But, you know, we’re not stupid. We know that our Facebook friend that we actually never see, you know, haven’t seen in years is not the same thing as your best friend that you call when something good or bad happens in your life, you know. And so there are real differences in what we mean by the term friends. So that was one thing. But also it’s, it’s just understanding how critical, from birth basically, your social life is and that you’re, so when you talk about, you know this gun viol, the episodes of gun violence and the, you know, I, I don’t have the answers for all of that, but I am sure that that kids who are really feel connected are just much less likely to go down that path. And I think it’s, we need to understand, I think with children anyway, often we are pushing them to accomplish things and they seem obsessed with their friends. And as a parent, you know, we sometimes say, well, okay, your friends are great, but you know, you need to do this. And, that’s not untrue at times, but I do think it’s really important to stop and check ourselves and say, wait a minute, are we making sure that they are building relationships that they need?

And even before that, as a parent, understand that in those early years of life, you’re not just sort of teaching them to walk and talk and sheltering and feeding them. You’re building their social brain, you’re teaching them how they’re going to go out in the world and be a social individual. And then when they get to the beginnings of school, they are getting a different lesson from peers, which is an essential lesson. And it’s about cooperation and trust and you know, and loyalty and things like that that are, that the better you get at that, the better your social skills, the sort of more success you’re going to have, frankly.

HEFFNER: The most important origin I would hope is the Golden Rule. You said two things that interest me greatly. One is about feeling connected and the other is about friendships outside of the family. But you do ultimately I think want to have your mom, or dad or grandparents or uncle, aunts,


HEFFNER: …Cousin, nephew, as friends. You want them to be friends too.

DENWORTH: You do, you do. So I think this is one of the really interesting things. So this new science of friendship both blurs the lines between family and friends and also helps us to try to understand the differences. So, the word friend is qualitative, right, it’s, it’s about a relationship and emotion. And it tells you if I call someone a friend, it tells you something about how I feel about them. It should. And if I, you know, refer to my husband or my son or my siblings, that those words are, they’re categorical. They tell you how we’re connected. But they don’t actually tell you anything about the quality of our relationship, which is why people use the term, you know, when people like to say that their spouse is their best friend but they do that specifically to tell you that their marriage is good.

HEFFNER: Qualitatively, right.

DENWORTH: Qualitatively, exactly. To add to what you know about that marriage. And the truth is that marriage can, your spouse can be your best friend, but, but also not in, sadly in a bunch of cases. And, and in fact it for a long time we didn’t aspire to have our spouse be our best friend, you know, so but one of the things that is really important is quality. So quality, that’s what, it rises out of all of this science: in animals, in people, and you know, baboons and rhesus macaques, and, and that, that the stronger the bonds, the strong bonds have, they’re positive, they’re long lasting and there’s some reciprocity in there somewhere usually, not necessarily at every, you know, not, it’s not tit for tat every minute. And in fact, in humans, one of the wonderful things is we, we begin to lose the accounting the closer we get to people.

So we’re not saying, you know, I did this for you, now it’s your turn to do this for me. But you have to; you have to arrive at that, you know, that special place. But, the quality of the relationship, that’s why friendship is really like, it’s a template or it can be a template for all other relationships because when you think of your closest friends, you really think about the positive, the way that you treat each other positively. We don’t always do that with other people in our lives. And yet those strong bonds that are represented by a friendship are the ones that determine our health and our longevity.

HEFFNER: Unfortunately, there are those who would feel connected by virtue of tribe only. When I mentioned the rise of bigotry and new racism, you know, the new Jim Crow in this country, folks can feel connected to tribe more than friendship. And the consequence of that may be the mass murders we’re seeing, both the mental illness and the race-based modern Klan violence. So feeling connected, how can you assess the science of friendship differently because it is more fundamental than feeling connected and folks unfortunately can feel connected on chat rooms and then go out and massacre people because they’re not their same race or from the same country they’re from.

DENWORTH: Absolutely true. Absolutely true. And the work on the sort of neuroscience of empathy, I think is especially, it speaks to what you’re, what you’re talking about here. Which is that first of all, we understand now that they’re there in many ways there’s positive elements of empathy. When we think of empathy, we think of it as a good thing, but it also carries with it that kind of us/them that, that, in-group and out-group sort of element and, and you can see it. What I hope is that understanding how our brains work and that we do bring implicit bias, all of us into the world. There’s a lot of research that shows that – that then you have to, you have to be aware of it and then you have to work to counter it a little bit.

You know, the, you have to say, okay, I feel connected. I mean friendship has been based since time in memorial on similarity. It’s what we, you know, we’re drawn to people who are more like us than not generally. And that doesn’t have to be a bad thing, but it is something that we should be aware of. And it doesn’t mean that you know, some of the most wonderful friendships are friendships across generations or across races or, you know and that’s what we should strive for. But I think that it’s, it’s fair to recognize that, that there is this kind of basic sort of instinct to hang out with people who are somewhat like you, then to, and that’s okay as long as you are paying attention to, you know, or being self aware about what you’re doing and then making the effort to understand that other people are in fact also probably more like you than you think.

HEFFNER: The newness of the science,


HEFFNER: Does it reflect the aims of, of friendship itself and wanting to further enhance the quality of friendship? Or is it kind of an amoral science at this point?

DENWORTH: I mean, there are elements of biology that, you know, it just, the facts are the facts about how genes work and about how, you know, brainwaves work and things like that. And so we have to, I mean, that’s what the original sort of controversy about sociobiology and E.O. Wilson and all of that, which you know, is, is the beginnings of this new science of friendship was politically controversial because people thought that E.O. Wilson was saying or that the sociobiologists were saying that, you know, your genes drive what you do and therefore, you know, bad behavior is acceptable. It’s, just what we’re, it’s our natural instinct. That’s not what scientists today are saying at all.

They’re saying we need to understand the facts, the underlying biology and the evolutionary drive. But we also have the ability and the wisdom to counter it if we see the culturally that it’s not, what we want

HEFFNER: And how for our viewers who might be interested in your book, how would you say that that’s been embodied in your own friendships and your tracing the science of, of your own friendships?

DENWORTH: Well, they’re just, this sort of: The beginning of it is simply that friendship. I prioritize it in my life. You know, I make sure that I am paying attention with, as a parent, as a spouse, I think it’s really important that people encourage their significant others to work on their own friendships outside of the marital or romantic relationship, you know, which sometimes doesn’t happen. It’s important that parents give their kids time to; I mean, just let your kids have sleepovers. Let them really spend time. I mean, this is one of the fundamental things about friendship is that it takes time. It takes time. Even if you like somebody, the minute you meet them, it takes time to really develop the bond that is going to sustain you. And so you need to put in the time. You need to invest. So that’s like a, just as a big ticket I mean, how does it affect my life? It just changes, you know, that that time where you think, oh, I’m too busy. I’m not going to do the, you know, I’ll see this friend another time. You stop and you say, well, maybe not. Maybe I should prioritize this right now, maybe. And you know so there’s that. But I also do feel that I understand on a deeper level that my health depends on it, that, friendship is a public health issue, you know, that if it is,

HEFFNER: Oh yeah, you know, that’s well said, because in this political climate there, people often riff on, you know, the strength of their friendship and whether or not politics can get in the way. I mean, I was wondering if that’s something that you grappled with in writing this, thinking about, you know, the fact that sometimes you need a base level of values,

DENWORTH: Of values, you do. In fact, I think one of the really interesting things is that worldview is one of the things that is most, most draws us together with, with someone else. And, you know, it doesn’t, you don’t have to have similar personalities, you don’t, you know, but, but that in, a bunch of different studies including way back at the University of Michigan, the, one of the studies I love is that in the early sixties this guy Theodore Newcomb at University of Michigan had the idea, it’s like reality to be before, you know, it’s or before reality TV was a thing.

And he put 17 incoming transfer students to the University of Michigan into one house together and he watched them interact and make friends and then he asked them every week, you know, to talk about who they liked and why and, and he tracked how much time they spent together and all of that. So, you know, just to try to understand what pulls people together and what drives them apart or what, you know how, cause you can spend a whole lot of time in proximity with someone and not like them very much or just not become friends. You know, we do that with people we work with all the time. We’re friendly, but we’re not, you know, we’re not deep friends.

HEFFNER: Right. Exactly.

DENWORTH: That’s fine. That’s good. You know, that’s the way it should be. You should be being somewhat selective. I mean, that’s actually the fundamental point of friendship is that I like this person, you know, especially. I’m closer to this person.

I’m partial. It’s, it’s a, there’s a sort of discriminative nature to the relationship. Which by the way is one reason philosophers didn’t like to study friendship because it sort of, it said that, you know; you were supposed to be loyal to God first. Actually the moral philosophers or the Christian philosophers didn’t like it because they thought it got in the way of religious thought and then others because it got in the way of sort of moral action because if that’s true that you’re more partial to this person, then maybe you’re going to not act for the universal greater good. You know? I get the philosophical argument, but I think that in fact having those strong bonds, you know, is, has been a force for good for most people and that we are driven to cooperate just as much as we are driven to compete. And that, friendship comes out of that evolutionary drive to cooperate.

HEFFNER: And when does friendship become love?

DENWORTH: It may be that love comes first and that you, you know, if you’re, I mean, if you’re going to have romantic passion for someone that’s, that is something different. It’s, it’s another level of,

HEFFNER: Right. Although sometimes you’ll say to your bestest friends, you’ll say, I love you man. Or I’ll go,

DENWORTH: Oh, yes.

HEFFNER: And that is love has different

DENWORTH: Right? Right. Okay, so. 200 hours: That’s how long it takes to have to call someone a best friend to think of someone as, so there’s a researcher at the University of Kansas, Jeff Hall, whose work I really enjoy and who actually measured the amount of time and investment it takes for people to consider someone, a friend. And it was 50, about 50 hours just to go from an acquaintance to a friend. And then there are these other cut points. But for a best friend, you really needed to have spent about 200 hours together. And those 200 hours need to be engaged in something a little bit meaningful, you know, either sharing, it doesn’t have to be self-disclosure, I don’t have to tell you the whole story of my childhood and all my hopes and aspirations and you know, disappointments in life, right, right away. But catching up, even if you ask someone, tell me what’s going on in your life that shows that you are interested, right. And so that kind of conversation and interaction helps to build friendship. And so, yes. So apparently it takes 200 hours

HEFFNER: And truth telling, candor, isn’t that real ingredient here.

DENWORTH: It is, although it’s interesting because if you think about quality relationships and we think about wanting that positive bond, you also need to be kind. So you need to find that balance between, you know, being truthful but also being kind. And you know, I mean it is funny. It makes me laugh because you know, I can really snap at my family members for how they load the dishwasher, right or something silly like that. But I wouldn’t do that to my friend. You know, I might just sort of live with it or, you know, and so I, which is not to say that I don’t, I, because of course I’m raising three boys I need to teach them how to load the dishwasher well so that, you know, I take this off the plate of their future partners. But the point is that it, I do think sometimes we should stop and we should think about how we treat all of the people, all of the different people in our lives and some relationships we sort of allow ourselves a little bit less kindness and our friends, we tend not to be that way with, you know and so I think we can take a little something, I’m not trying to be Pollyanna-ish here because sometimes real, you know, hard truths need to be said.

HEFFNER: Where is the research going right now?

DENWORTH: So it’s fascinating. One of the so the neuroscience really intrigues me. They’re trying to look at the brains of two people as they interact and essentially capture friendship while it’s happening.

And, the idea is, is there some place that your brains go when you’re interacting with a friend that they wouldn’t get to on their own? And can we see it? Can we see it in a brain scanner? And you know, what we do know is that and just in the last year or two, we know that your, the way your brain processes the world is more similar to the way your friends brain processes the world than it is to people to whom you’re not as close. And so, and by that I mean literally like the way you look at a video or listen to something, is different from somebody else’s. And the question is, do you and your friend process the world the same way and that’s part of what draws you together. I mean, you can’t know it; you can’t look at someone and say, I see how you are, you know, auditory cortex is operating but you, but you might end up being drawn to each other or do you become more similar as you are together? And we don’t know the answer yet. They’re working on that, but that, you know, probably it’s a little of both. You know,

HEFFNER: You had alluded to the idea that friendship was abstract as a science and therefore it was relegated or dismissed, but it’s also so subjective,


HEFFNER: You know, and it’s how we assess, well, are these the two people whose brains we want to monitor, you know, is that really our definition of friendship? And then it comes back to values too.

DENWORTH: Well okay. But in that study, for instance, of monitoring frame, you know, there, there are many, many people in the study. Well, yeah, I mean, you know, there’s a limit to how many people you can run through the scanner so those, those, they’re not thousands of people, but, but it’s not just picking two people.

HEFFNER: I understand. I’m just wondering, were all those people how strict the criteria is or by what they’re judging the criteria to admit them to the study?

DENWORTH: Well, in that particular case, they all happen be students in a graduate program. And so they brought them together. You know, they tested them right when they got there. And so then they can follow them over time.

HEFFNER: I think your hours criteria is a smart one, an objective one.

DENWORTH: Yeah. Yeah,

HEFFNER: And I don’t know if that’s the conclusion of the friendship academia community, but the number of hours,

DENWORTH: You know, I, what I loved about the number of hours is just that, you know, nobody had ever counted that before and …

HEFFNER: You’re accountable.

HEFFNER: Right. And then you’re accountable. Exactly. Thank you so much for your time today, Lydia.

DENWORTH: Thank you very much.

HEFFNER: And thanks to you in the audience. I hope you join us again next time for a thoughtful excursion into the world of ideas. Until then, keep an open mind. Please visit The Open Mind website at to view this program online or to access other interviews and do check us out on Twitter and Facebook @OpenMindTV for updates on future programming.