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Essential trust: Trust in the animal kingdom

Chimpanzees Bahati and her baby Baroza at Gombe National Park, Tanzania. (© The Jane Goodall Institute/Anna Mosser)
Chimpanzees Bahati and her baby Baroza at Gombe National Park, Tanzania. (© The Jane Goodall Institute/Anna Mosser)

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This is part one of our special series Essential trust. This rebroadcast originally aired September 19, 2022.

Jane Goodall formed incredible bonds with chimpanzees in the wild.

“First they were afraid. Then they became belligerent. And then when I wouldn’t go away, ‘Well, I guess she’s okay.’ They came to trust,” Goodall said.

But were those bonds similar to what we humans experience as trust?

“It’s very rare in the animal kingdom that trusting relationships can be established across community borders,” Prof. Jan Engelmann said.

In fact, the ability to trust strangers may be one of the things that makes us uniquely human.

Today, On Point: We’re launching our special series ‘Essential trust: What trust is, why we need it and what happens when its lost.’


Jan Engelmann, psychology professor at UC Berkeley.

Lee Alan Dugatkin, professor of biology at the University of Louisville. (@LeeDugatkin)

Also Featured

Marc Bekoff, professor emeritus of ecology and evolutionary biology at the University of Colorado, Boulder. (@MarcBekoff)

Show Transcript

MEGHNA CHAKRABARTI: Have you stolen money from the association? She leaned in. Her face filled the Zoom box when she shouted again. Have you stolen money from us? I was shocked, confused, and did not know what to do. I’d done my very best to responsibly serve as trustee for our condo association, and there was no way I’d ever steal anything from anyone.

And here was a fellow owner accusing me of criminality. Well, our condo manager stepped in and said, No, the trustees have run the association just fine. I wanted to add, is there any specific? Don’t talk! She shouted at me. I don’t believe anything you say. Silence. The condo manager tried again. All our correspondence and all the association’s finances are available for any owner to read on the portal, he said. I will, she said, and then snapped off her Zoom camera so angrily I could hear her finger smashing against the computer. It made me flinch. And it still does.

This is On Point. I’m Meghna Chakrabarti. That was almost a year and a half ago, during a really tough time in the pandemic. My fellow condo owner and I hadn’t seen each other in about a year, and to this day I still don’t know why she was so angry, because we haven’t really seen each other since. All I knew is that she did not trust me. Now you’re going to ask, well, Meghna, why didn’t you just ask her after things cooled off? You know, build bridges and stuff. Fair enough. But — and this doesn’t say anything good about me — after that day, after being frivolously and unfairly accused of theft, I did not trust her either. Whatever bridge we had gotten burned down to the ground.

And frankly, to this day, every time I think of that meeting, I don’t feel the rational part of my brain responding. Nope. I feel the lizard part of my brain, going into overdrive. Stress, anger, high heart rate, that sort of thing. The opposite of clear thinking. So the only thing I can say clearly now that I learned from that day is that trust is a strong bond. But when broken, it is very hard to mend. Now take my one pitiful example and scale it way up, because trust is also the bond that holds entire human societies together, including ours here in the United States. That bond, though, is straining to hold. And in some areas of American life, it’s breaking or already broken. Take, for example, public trust in government.

Pew Research has been polling Americans since 1960 on this question, and they find that as of May 2020, barely 20% of Americans say they trust the government to do what is right most of the time. In 1964, that number was at 77%. It began falling during the Johnson and Nixon administrations, recovered a little during the Clinton administration, but has never, ever come close to that almost unimaginable high watermark of the 1960s. Gallup has been asking a similar question. They have been polling Americans’ trust in 16 different institutions, everything from the military to public schools, tech companies, the media and every branch of government. And they too find that trust is plummeting. Barely 7% of Americans say they trust Congress. 23% say the trust in the institution of their presidency is high. And by the way, that’s in the institution of the presidency, not just the person occupying the office.

28% say they trust public schools. In fact, the only two institutions that earned more than a 50% trust rate? The military and small business. And by the way, in every single one of those polls, the decline in trust is similar, regardless of the respondents’ political affiliation. So it doesn’t matter what party you belong to, what your values are, or what you believe. In 2022, you trust almost every American institution far less than your parents or grandparents did. Well, we’ve been thinking a lot about what this means for this nation, for its present and its future. And more fundamentally, we want to understand in the most elemental way possible that bond that holds us together. We want to understand the concept of trust.

So we’re going to spend all this week bringing you a special series that we’re calling “Essential trust.” And we start today with a question that’s as big as it is simple. Is trust uniquely human? Or is it something that’s intrinsic to every cooperative and social species across the animal kingdom? And if so, what can we learn from them?

Now, if there’s anyone who’s formed what looks like a trusting bond with animals, it’s famed chimpanzee researcher Jane Goodall. But that trust didn’t come easy in her years of studying chimpanzees in Africa. Goodall was actually attacked several times, including a near-death experience. Once … a chimp she’d named Frodo grabbed her and dragged her down.

JANE GOODALL: Stamped on me. It hurt. Bashed my head onto a rock and it was bleeding. And then he … went away and I thought, Oh, well, I’ve survived. And then he came back and did it again. And then he pushed me over the edge. And if there hadn’t been some little bushes growing there, I wouldn’t be here now, because it was a way big drop.

CHAKRABARTI: Goodall was willing to endure such experiences because she wanted to learn up close about the relationships between chimpanzees, themselves. But as she explained to CBS’s 60 Minutes in 2010, she also believes that studying chimps had the benefit of revealing a lot about human nature.

GOODALL: We’re part of the animal kingdom, not separated from it. We could have a blood transfusion from a chimp. If you match the blood group, you really could. And the other way around, too. People say to me, thank you for giving them characters and personalities. I didn’t give them anything. I merely translated them for people.

CHAKRABARTI: And what Jane Goodall saw in the jungle, she says, was a mirror to human society.

GOODALL: It was obvious watching them that they could be happy and sad. And then the communication signals. Kissing, embracing, holding hands, patting on the back, shaking the fist, swaggering, throwing rocks. All of these things done in the same context we do them.

CHAKRABARTI: Is it the same context? And specifically about trust. Do animals experience and demonstrate trust in the same way that humans do? Well, joining us now is Jan Engelmann, assistant professor of psychology at the University of California, Berkeley. And his work seeks to answer this question, How are human skills and motivations for cooperation similar or different from those of our closest living relatives, the chimpanzees? Professor Engelmann, welcome to On Point.

JAN ENGELMANN: Hi Meghna. Thanks so much for having me.

CHAKRABARTI: So do chimps demonstrate what we as humans would recognize as trust?

ENGELMANN: I would say that depends on the kind of trust that you’re talking about. So there are different forms of trust. There’s the kind of trust that you have maybe in your close friend who you have known for many decades. And I think that kind of trust chimpanzees also show. But if you talk about the kind of more institutional trust that you referred to at the beginning of the show, trust in government, trust in schools, trust in banks and so on. I don’t think chimpanzees show that kind of trust.

CHAKRABARTI: Well, one would argue that they don’t have those kinds of institutions, but maybe trust between troops of chimpanzees, which I’ll come back to in a second here. But let’s talk about this in detail. Take us inside the social dynamics of a group of chimpanzees. How do they demonstrate to each other what we would recognize as that sort of, let me call it intra-familial trust?

ENGELMANN: Well, they engage in many high risk cooperative activities together. So, for example, they engage in border patrols as a group, where they really have to trust each other, that they don’t run away, for example, when they encounter a neighboring group. They share food. When one chimpanzee has found some food, they might share it with another chimpanzee. And, you know, at a later point, the second chimpanzee might reciprocate. And also in their fights for dominance, they have to trust each other because often they fight as an ally for dominance. They don’t fight on their own.

CHAKRABARTI: Okay. And they live in groups of what? I mean, how large is a typical chimpanzee troop?

ENGELMANN: So I would say the typical chimpanzee group is about 40 to 50 individuals. The biggest group that has ever been observed lives in Ngogo, which is in Uganda, in Eastern Africa. And that group has 150 individuals.

CHAKRABARTI: So that’s that’s quite large. And even the 40 to 50 individuals, that doesn’t seem to be like a very easy number in which to form trusting bonds between all members of of the troop.

ENGELMANN: That’s 100% correct. And that’s actually what chimpanzees spend most of their waking hours doing is investing, and managing and repairing relationships. By grooming, by sharing food, by engaging in other kinds of social activities.

CHAKRABARTI: So tell me more about that, because I want to understand, you know, what that development and maintenance of trust looks like between chimps. What what else have you observed?

ENGELMANN: So I mean, the development of trust is actually a really interesting question. So you can ask, How can one actually establish a trusting relationship? And, you know, in the literature, two types of, or two forms, are described. One is called testing the water. So if you want to establish a trusting relationship with someone, you first, you know, you invest a little bit in the relationship, and you see whether they reciprocate, whether they are trustworthy.

And then you increase the stakes as you go. Another way in which you can establish a trusting relationship is by what’s called a cooperative leap of faith. So in the human case, or maybe even in a chimpanzee case, you know, a person that you’ve just met, you can give them your kids to babysit. That would really be a cooperative leap of faith, and a really strong test of whether they are trustworthy. And I think chimpanzees use both of these methods. So they’re used to testing the water method and the cooperative leap of faith method.

CHAKRABARTI: You’re listening to episode one of our special weeklong series Essential trust. Today, we’re … asking what we can learn about this fundamental experience of trust from chimpanzees, from elephants, from the insect world, from bees and termites, even. What is it about trust that makes it so uniquely important for any pro-social or cooperative animal species? And I’m joined today by Jan Engelmann. He is a professor at the University of California, Berkeley. And his work tries to answer the question about how humans skills and motivations for cooperation are similar or different to those of chimpanzees.

Now, Professor Engelmann, so you had talked about how chimps spend so much time, so much of their waking time actually developing and maintaining these trust bonds within a troop. But can you tell me even more about the development part here? Because I can imagine that chimps that are born into the troop, there’s a certain amount of trust built in there. You’re born into the troop. But do other chimps from outside the troop join? And if so, how is that trust built? What is that process like?

ENGELMANN: So I would say actually that’s one of the main differences between trust in humans and trust in chimpanzees. We humans, we live in the company of strangers, right? All day, every day, wherever we are, we are surrounded by people who we have never met before. And we somehow manage to trust them. Chimpanzees all day, every day, they’re surrounded by members of their group. They’re surrounded by individuals who they know very well. So this kind of trust in strangers that humans at least sometimes have is human unique, I would say.

And in chimpanzees, one of the main ways to establish trusting relationships is through grooming, through the exchange of grooming. So, for example, what you could imagine is that one individual starts grooming another, after 10 minutes or 15 minutes or so of grooming. They expect reciprocation. They expect to be groomed in turn, and then their partner can either prove trustworthy by grooming them or prove untrustworthy by moving away. So that would already be a small sign that chimpanzees use that this specific partner is trustworthy or not.

CHAKRABARTI: But as you’re saying, though, the first interaction with a stranger chimp, for example, is not one that’s based on almost instantaneous, at least a small amount of instantaneous, trust. It’s more sort of an aggressive initial reaction.

ENGELMANN: Oh, yes. So when the stranger is someone who’s from another group, this interaction would basically never be cooperative. This will always be an antagonistic, aggressive relationship. The one exception to this is when female chimpanzees switch groups, which is an extremely nerve wracking process for these adolescent female chimpanzees. But that’s sort of the only time in a chimpanzee life where there’s really a cooperative interaction between groups. What’s maybe interesting to point out here is that we have two closest living relatives, right? We have chimpanzees and bonobos, and we’re equally closely related to both of them. And in bonobos, you actually see more peaceful, more cooperative, more trusting interactions among different groups.

CHAKRABARTI: Oh, that’s fascinating. And do you hazard to guess why that is?

ENGELMANN: I don’t think we know yet. The jury’s still out on that one. But one hypothesis out there is that in bonobos, there’s less competition for food. So bonobos don’t have to be as territorial as chimpanzees.

CHAKRABARTI: Okay. Now, so within the troop structure of a group of chimpanzees, is a lot of what we’re seeing as trust sort of sorted out, because is there a very strict hierarchy in in the group? I don’t know if I want to say it makes it quote-unquote easier to form trusting bonds. But how does the group hierarchy factor into this?

ENGELMANN: Yeah, that’s a good question. So there’s a very strong hierarchy, there’s no doubt about that. And of course, having that kind of hierarchy generates certain rules or comes with certain rules. So low-ranking chimpanzees know exactly what they’re allowed to do and what they’re not allowed to do. So I would say that generates a certain form of trust. But more than the hierarchy, what I would say what generates the trust is just the wealth of personal experience that individual chimpanzees have with one another. So they have a lot of data, so to speak, from which they can see whether someone is trustworthy or not.

That’s what makes trust among humans or in large scale human society so hard to generate, is that many people that we live with in the same community, even in the same city, we have never met them before. So it’s really hard for us to assess whether we can trust them or not.

CHAKRABARTI: But clarify something for me. Maybe you said this earlier, but if chimps have this wealth of data about whether another chimp is trustworthy or not, what data is that?

ENGELMANN: Well, data, like when I’ve groomed that chimpanzee, did they groom me back? When I needed this chimpanzee support in a fight, did they support me? When I went onto that Border Patrol, did that chimpanzee come with me? Or did they leave me stranded there?

CHAKRABARTI: I see. Okay. So they’re basically using actual evidence of mutual behavior patterns between the chimps. That’s interesting. So, again, this brings you back to what you were saying earlier, that this is one of the things that you say differentiates humans from chimpanzees, that we’re forming some kind of trusting bond on almost no data regarding the people that we meet.

ENGELMANN: Exactly. That’s the really fascinating thing. And, you know, for me, I’m sometimes surprised how granted people take the fact that we can live a life that is surrounded by strangers. Because no other great ape species does anything that’s similar. So how is that possible? How can we generate these trusting and peaceful relationships with strangers?

I live in San Francisco. I have at least 2 million people around me all the time. The vast majority of those people, I don’t know them. I’ve never met them before. And still we somehow can sort of get that corporative endeavor that is a city going.

CHAKRABARTI: Okay. Well, one more question before I want to bring in another guest into this conversation. But does trust break down between chimpanzees? And if so, how does that happen and what’s the consequence of that?

ENGELMANN: Well, it sure does break down. Chimpanzees, just like humans, they’re not perfect, trustworthy partners. So I remember, for example, one instance where one chimpanzee was engaged in a fight, and they expected their friend to support them in this fight. But then the friend, for whatever reason, didn’t join them in the fight. And you could just see so clearly how the chimpanzee felt betrayed by their friends, how they felt like all this trust that they had been building up over years in this relationship had broken down. Because chimpanzees, like humans, they form really long term cooperative relationships of ten or 15 years.

And, you know, for that specific relationship, it took a lot of time for it to be reestablished, for the chimpanzee to trust their friend again. And what did the friend have to do? Well, the friend had to really significantly invest into the relationship for a long period of time. So they consistently shared food. They groomed, they supported the friend following this instance.

CHAKRABARTI: Wow. Okay. So I’m going to come back to that a little bit later in the show, because what you just said sounds very familiar. … But stand by for just a moment, because I want to now bring in Lee Alan Dugatkin. He’s a professor of biology at the University of Louisville in Kentucky. … Welcome to On Point.

LEE ALAN DUGATKIN: Thank you very much. I’m delighted to be here.

CHAKRABARTI: Let me just ask you, I keep using this word trust in talking about the animal kingdom. But is what the chimpanzees are experiencing … is it fair to call it trust? Or is it something more basic to sort of an evolutionary imperative that helps lead to survival? Are we putting too sort of a higher moral premium on this concept of trust in animals?

DUGATKIN: Yeah, I think that’s a great question. I would say that what Jan was describing with the chimpanzees certainly is trust. I tend to work more with things like fish and the like. And when you start talking about trust, I think it’s really important that you have a kind of clear definition in your mind of what you mean, because, you know, we can kind of say we feel like the chimps are doing human-like things.

But when you’re working with guppies, like I’ve work with, you really want a definition. And so for me, trust means sort of a confidence that an individual is going to behave in the way that you expect them to behave. And, you know, it is a kind of basic moral system that trust builds up evolutionarily. But that doesn’t mean that trust is not a very selfish thing. In other words, I can invest in trust if it benefits me, even if a side effect is that it allows for kind of a societal structure to exist. But the evolutionary forces might be really, really selfishly oriented.

CHAKRABARTI: That makes total sense to me, right? Because the king gene as we can call it wants to want to survive as much as possible. So the selfish benefit then makes sense that it would lead to these more cooperative societies. But then you have to kind of ask the flipside of that question … why don’t we see more species that are pro-social or cooperative?

DUGATKIN: Well, I would say that when we actually spend the time to kind of deeply probe species in nature, we often find that there are cooperative aspects to most group living species that we study. They may be rudimentary, they may be different from group to group, but they’re there. So for example, the sort of thing that we were hearing about in trust with the chimpanzees, the guppies that I studied, for example, you know, the tiny fish you would see in the aquarium story, except we get them from Trinidad, where they swim around.

They do something. It’s not Border Patrol, but what they do is if there’s something dangerous out in the environment, they go out and check it out to see, in fact, how dangerous is it. And when they do this, they keep track of other fish. And whether those other fish are willing to stay by their side and take the risk with them or not. And then you can test them experimentally and you can show, you know, they prefer to hang out with individuals who have stayed by their side during risky situations.

I would say that’s an example of trust building up. It’s personal experience that allows a guppy in this case to know this other guppy is somebody who will stay by my side. And this one over here is somebody that’s going to bolt out as soon as it’s dangerous, and that’s going to hurt me.

CHAKRABARTI: But is what you’re seeing with the guppies … is sort of the result of complex information processing? You know, we primates like to think that we’ve got these big brains that can really take in a lot of information and come up with sophisticated conclusions from the information. Are they just responding sort of instinctively?

DUGATKIN: Yeah, well, they may be responding instinctively, but that doesn’t mean it’s not really complex. So, for example, when this danger is out there in the environment, some potential danger. They’ll start off with a low level of trust, meaning they’ll move out together. But then once that happens, they are keeping track of whether or not another fish is this close to them, or that close to them. Are they lagging behind or are they not?

And then also, once a fish, another fish has demonstrated it’s not trustworthy, then again, like the chimpanzees, but at a much more rudimentary level, you have to reestablish that bond. So if someone has shown you that they are not trustworthy, when you’re going out and looking at danger and guppies, then for you to trust them again, they actually have to lead the next foray into a dangerous situation. So it’s not just that they have to stay by your side in the future. They’ve got to show you that they’re going to take the lead on the next one for you to reestablish a kind of bond with them.

CHAKRABARTI: And this is among guppies.

DUGATKIN: That is right. And we’ve seen it in other species as well. But in guppies, it’s sort of remarkable because, you know, their brain can sit on the head of a pin.

CHAKRABARTI: Do a group of guppies ever end up ostracizing a guppy that’s proven not to be trustworthy based on the criteria you just mentioned?

DUGATKIN:  No, I don’t think so. And maybe this is sort of a distinction between guppies and primates. In that what’s going on there is very much a kind of one on one thing. So a fish keeps track of another fish. But there are no kind of decisions that are made at a group or societal level where they all kind of boot out an individual who has, you know, over and over again, shown themselves to be non-trustworthy. Instead, a given individual would view another fish as untrustworthy. But it’s not a societal level thing in these fish.

CHAKRABARTI: Professor Engelmann, let me turn back to you here, because I want to ask you, I was really taken by when Professor Dugatkin said, Just because something is instinctive doesn’t mean it’s not complex. So let’s apply that to the chimps. Would you say that what we’re interpreting as acts of trust or trust building is also, in fact, very instinctive in the chimpanzees? Like, do they just want to very deeply and fundamentally form trusting bonds?

ENGELMANN: Yes and no. So I would say on the one hand, it’s very instinctive. Because chimpanzees, like humans, cannot survive on their own. They need the group. They need those trusting relationships. But on the other hand, it’s also very, very flexible and very cognitively sophisticated. So what professor Dugatkin was referring to a couple of times is what in the literature is referred to as partner choice.

So when we engage in co-operative endeavors, we carefully select certain partners to interact with. And we select those partners that are trustworthy, that are cooperative, that we can rely on. And chimpanzees do a lot of that kind of partner choice. What chimpanzees don’t do, however, and this is somewhat puzzling to me, but many, many experimental findings have proven that, is chimpanzees don’t really seem to care about their reputation.

So as humans, we don’t only want to choose trustworthy partners, but we also want to make sure that everyone knows that we are trustworthy. The first rule of social life in humans, as many have have said, is don’t lose your reputation. Make sure that everyone sees you as trustworthy. And that’s something that chimpanzees, interestingly, don’t seem to do. They don’t worry about their reputation.

CHAKRABARTI: You’re with us for episode one of a special series we’re doing all of this week called Essential trust. Today, we’re asking what can we humans learn from the animal kingdom? And Professor Jan Engelmann joins us. He’s at the University of California, Berkeley. He studies chimpanzees. And Professor Lee Alan Dugatkin joins us. He is at the University of Louisville in Kentucky, is a professor of biology. He studies guppies. Professor Engelmann, just before the break, I blurted out, Wait, how does the chimpanzee know what its reputation is? I’d love the answer to that question.

ENGELMANN: Yeah. So we ran a series of studies where we investigated whether chimpanzees would share more, so present themselves as trustworthy, when they were observed compared to when they were alone. So in one condition they were observed by others, and in the other condition they were completely on their own. And we didn’t find any difference between these two conditions. So for chimpanzees, it doesn’t really seem to make a difference whether they engage in a behavior while they’re alone or while they’re observed by an audience.

The interesting thing is that this concern for reputation seems to be extremely, deeply ingrained in human nature. So already very young children, we have found that children at around four years of age, they, in contrast to chimpanzees, really care about their reputation. So they help more. They share more. They present themselves as trustworthy when they’re observed, when they are alone in the room. They certainly don’t help so much anymore. They don’t share so much anymore. So this sort of desire to present us as trustworthy seems to be really important for humans.

CHAKRABARTI: Professor Dugatkin, I’d love to hear if you have a comment on that. And then I also want to know if what we think of as trust, you talked about the guppies, but I keep coming back to the insect world. Bees, ants, termites. I mean, are they behaving in a way that we could identify as trusting?

DUGATKIN: Sure. Yeah. Well, with respect to the experiment on chimpanzees, I think those results are actually quite, quite fascinating. And within animal behavior, you know, there’s this growing interest in what are called audience effects, the notion that you will behave differently depending upon who’s watching you and who isn’t. And just one other quick guppy thing, and then I’ll get to the insects. So in our guppy system, I wouldn’t say there’s reputation, but there is something interesting going on with respect to sort of who’s watching you.

So I did this experiment with a colleague of mine … where we basically set it up so that the fish could go on these explorations to look at dangerous situations. And we were looking at males and we asked the question, are the males more likely to go out on one of these dangerous expeditions if they’re being watched by females, versus being watched by males or being watched by nobody?

And therefore, the answer was, in fact, yes. That when it comes to advertising yourself as a particularly good mate, someone who’s willing to take risks that might help your partner, for example, they seem to care. I don’t know that that’s reputation. But it’s fascinating nonetheless. So with respect to the insects and whether trust is going on there, within evolution and animal behavior, we tend to think of certain things that kind of foster cooperation in general and trust in particular. And we’ve really been focusing so far here on keeping track of information, reciprocity, these sorts of things.

But another thing that’s really important is how genetically related individuals are. And in the social insects, in particular, bees, ants and wasps, you know, genetic relatedness is very high. They have a kind of weird genetic system where they’re even more correlated to brothers and sisters than, say, humans are to brothers and sisters. And the reason this is important is that what you need is confidence that an individual is going to behave the way you expect them to behave.

Now, if you share a lot of genes with individuals in the group that you’re living in, then you don’t really need to rely as much on personal experience. If you are a cooperative, trustworthy type, then the odds are that your genetic relatives are also cooperative and trustworthy, because you share the same genes. And so there I think there’s a kind of trust, but it’s based on a different system.

CHAKRABARTI: Okay. Oh, that’s interesting. So, Professor Engelmann, let’s just go quickly back to the chimps. What you were describing earlier, though, is even in a troop where there’s, you know, the chimp version of a lot of genetic similarity, because they’re blood relatives of each other. You can still have, though, the real sort of profound breakdown in trust between individuals.

ENGELMANN: Absolutely. And I think what’s important here to point out is that, of course, we see cooperative social relationships among relatives and chimpanzees. But many of what I would call friendships that we see in chimpanzees are actually among non-related individuals.

So the kind of mechanisms or the kind of mechanism that Professor Dugatkin referred to, which is called kin selection, which explains cooperation among related individuals, cannot account for these kind of friendships that we see in chimpanzees. So chimpanzees are extremely similar in this regard as humans. They also form very, very long lasting, cooperative relationships with non-related individuals.

CHAKRABARTI: Well, I want to just turn the corner a little bit and talk in more detail about what the consequences are in various parts of the animal kingdom when trust is broken down. And for that, we spoke briefly with Marc Bekoff. He’s a professor emeritus of ecology and evolutionary biology at the University of Colorado, Boulder.

And he’s spent most of his career looking at wolves and coyotes. And his work has shown that being untrustworthy, being an untrustworthy animal is, in fact, downright dangerous. For example, one of his studies involved spending 5,000 hours. He spent 5,000 hours observing one pack of wild coyotes.

MARC BEKOFF: We were able to watch individual wild coyotes when they were young. And young coyotes who invite other individuals to play and then play roughly or deceive them, or young coyotes who just play roughly, and just don’t know how to control their behavior. They tend to leave their … natal group, their birth group, their pack and go off on their own and they suffer much higher mortality.

CHAKRABARTI: So those are individuals that leave, but the group at times also ostracizes them. Because if you can’t be trusted, you’re ostracized. And as what might be familiar, when you’re ostracized in the animal kingdom, you’re very likely to die, as the professor just said. Now, some scientists object to applying human concepts like trust onto animal behavior. But over his career, Marc has become convinced that there’s only one thing you can call the behavior he’s observed.

BEKOFF: Certain signals have evolved for me … to communicate to you that my intentions are to play, not eat you, harm you, fight with you. Dominate you, mate with you. I mean, you know, frankly, I see no problem using words like trust because to me, trust is one of the basic ingredients of having a coherent group, a pack, a flock, a herd of animals.

CHAKRABARTI: And he also says it’s clear that trust doesn’t need language or even, you know, a society at the level humans express it to exist.

BEKOFF: Somebody once said, well, you know, they don’t sit around and talk about it. Well, I don’t talk about it either. I don’t talk to a driver driving down the street assuming you’re going to stop at a stop sign, you know? So I don’t buy that. And as far as anthropomorphism goes, I don’t even talk about it anymore. Most of us don’t. It’s just useless. I mean, I’m not saying dog trust is the same as human trust, and I’m not saying dog trust is the same as wolf trust. But the basic ingredient is that I have this feeling that another individual, in addition to their best interests, has mine in mind, too.

CHAKRABARTI: We’re making the assumption that in human society, when trust is degraded or broken, that that’s bad for society overall. I mean, that’s the entire animating force for our whole week of conversations here. But do we see evidence of that in the animal kingdom?

DUGATKIN: Yeah, it can be so. And the way that often manifests itself is, you know, not so much in the guppies, but in many other species, when you’re living in social groups, you know, you need to have a certain territory size. You need to get a certain amount of food that’s available. That’s enough to feed everybody in the group. And when you have trust breakdown and individuals aren’t, for example, cooperating with each other, to either fight off groups from the outside or expand their territory or get food, then what happens is that group becomes relatively less likely to, for example, expand its territory or take over a new territory than a group where trust doesn’t break down.

Now, I should just add that exactly what’s going on, evolutionarily, there is a really hotly contested topic. So there are some people that think that basically natural selection and evolution are operating at the group level, as well at the individual level. And there are others who say, no, it’s just individual care about groups, because they care about themselves. And if their group does well, they do well.

CHAKRABARTI: Professor Engelmann, let me ask you that same question, that when trust breaks down, you know, between individuals in a chimp troop, is that also bad for the troop itself?

ENGELMANN: Absolutely. … This is really bad for chimpanzees, chimpanzee groups, because their strength, their safety in numbers. So when you have a large chimpanzee group, the likelihood that they can expand their territories, that they can successfully fight against neighboring groups is very high. But if you’re a chimpanzee in a small group, then the likelihood that you will have a large territory is very low.

And this actually connects to your earlier point, about dominance and how it relates to trust in chimpanzees. It’s especially in contexts where the dominant status of different individuals is not clear that groups might break apart. So … in chimpanzees, two male chimpanzees who want to be alpha, and they both have support from different individuals in their group. And no one is ready to back down. This group may break up, and that’s bad for everyone involved.

CHAKRABARTI: You both have described what needs to happen within a chimpanzee group or within a group of guppies when quote-unquote, trust is broken and has to be rebuilt. In the case of the guppies, Professor Dugatkin, I heard you say that the untrustworthy guppy has to do things like really take additional risk, put itself at point for the group overall in order to prove that it’s trustworthy. And Professor Engelmann, you talked about the incredible amount of time and energy that a chimp has to invest in grooming and food sharing to rebuild trust.

So that seems to be one lesson that we as Homo sapiens can draw here, that it really does take an investment to rebuild trust. What’s another major lesson that you think we as humans should be drawing from the animal kingdom about trust and its importance? And Professor Engelmann, I’ll start with you.

ENGELMANN: Invest in social relationships. So as I said, when you observe chimpanzees, what they do, what they spend the majority of their waking hours doing is investing in relationships. You know, they call their friends, right? They talk to their friends, which they do by grooming their friends. And I think that’s something that we humans should also spend most of our waking hours doing.

CHAKRABARTI: Professor Dugatkin?

DUGATKIN: Yeah, I think that’s a good point. I also would say that, you know, if you’re interested in trust in humans, at a species level, you have a sample size of one. But if you can start studying this in chimpanzees and guppies and vampire bats and everything out there, then all of a sudden you can start looking for patterns. What underlies trust? What happens when trust breaks down? And maybe what we glean from all of that will help us develop and trust in humans.

CHAKRABARTI: Just briefly, what do you think underlies it?

DUGATKIN: I basically think that the individuals are investing in trust because in the end, it benefits them to sort of have some confidence that other individuals will help them when they need that help.

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