IRA FLATOW: This is Science Friday. I’m Ira Flatow. It wasn’t that long ago that scientists didn’t think animals could rival humans in terms of intelligence, emotions, or empathy, but the groundbreaking work of Frans de Waal helped to change all of that. De Waal spent his lifetime studying the lives of animals, especially our closest cousins, the chimpanzees. The primatologist died last week at the age of 75.

And we wanted to remember him by sharing one of our favorite conversations with him on the show. It’s from 2019, when he published his book, Mama’s Last Hug– Animal Emotions and What They Tell Us About Ourselves. In it, he tells the story of a female chimp who didn’t produce enough milk to feed her young. When de Waal taught her to feed her baby with a bottle instead, she repaid him with what most of us would recognize as gratitude, holding both of his hands and whimpering sadly if he tried to leave. It’s just one of the many fascinating stories of animal emotions he shared with me from Mama’s Last Hug. Let’s listen. Who was Mama?

FRANS DE WAAL: Mama was the alpha female of a very large chimpanzee colony at Arnhem Zoo in the Netherlands who I had known for 40 years. A very central figure– she was not physically dominant over the males, but she was certainly more powerful than most males in terms of her political connections and her skills of bringing parties together and so on.

And “Mama’s last hug” refers to her encounter with my professor, Jan van Hooff, who’s 80 now, who went into her night cage to say goodbye when she was dying. And so she embraced him. She actually calmed him down because I think he was a bit nervous going in there. We never normally would go in with an adult chimpanzee. So he was a bit nervous. And I think she calmed him down, which was typical of her kind of behavior.

IRA FLATOW: So what was that last hug like? You describe it in your book.

FRANS DE WAAL: Well, she embraced him and then tapped him on the back of his neck and his shoulders. And she had a big smile on her face. And she made some sounds.

And actually, people were, first of all, very moved by that encounter because it has been seen by, I think, 200 million people on the internet. So they were very moved. And I can understand that.

But people were also very surprised. And that surprised me. Why are people so surprised that a chimpanzee may express emotions in a very similar way, similar gesture, similar face as we do? Because chimpanzees are our closest relatives. So, of course, everything they do is extremely similar to what we do. And so I felt I needed to explain about facial expressions and about sounds that chimpanzees make. And so I took that as the starting point.

IRA FLATOW: Yeah. And you verified, for everybody who has a pet, that animals really do have emotions.

FRANS DE WAAL: Well, that’s interesting that you say that because the pet owners usually, as soon as you say, do animals have emotions, you say, my dog, and they go on and on. But in science, we have been extremely reluctant, unfortunately. I think we went through a very dark period in the previous century where a group of scientists, the behaviorists we call them, had decided that the inner lives of animals but also actually humans, the inner lives were irrelevant.

So for humans, for example, it’s only in the 1960s that we started to talk about the intelligence and emotional states and so on. And in animals, for sure, there was an enormous taboo that we lived under. And so I learned as a student that you shouldn’t be talking about emotions. It’s a word that you should not even mention.

IRA FLATOW: Yeah. In other words, if you saw a facial gesture, it was not an animal smiling. You would just describe it as how the muscles move, right?

FRANS DE WAAL: Yeah, yeah so if you tickle, let’s say, a chimpanzee, and the chimpanzee laughs, which they do, they have laughing sounds, like hu-hu-hu type sounds, they would say, why don’t you call it vocalized panting? So they would look for words that make the connection with humans obscure.

IRA FLATOW: You write in the book that some psychologists have argued that the emotions we feel must be more nuanced than those of the animals because we have language to describe what 12 different shades of anger– for example, displeasure, fury, resentment, just to name a few. What’s wrong with that?

FRANS DE WAAL: That’s based on the idea that language is at the root of things. I think language is a is a very late-appearing phenomenon in our species and also in the development. You wouldn’t say that a child who cannot speak has no emotions.

So language is irrelevant. Language is something we use to describe our feelings and to talk about them. And I can explain to you why I took a certain decision and how my emotions figured into that. So language is very good to talk about emotions, but they’re not at the root of the emotions.

IRA FLATOW: What’s been the reaction to you talking? I mean, this is one of your main themes and, it’s been for a while, that the animals have emotions. You talk about in the book about tickling a rat on its tummy. And it’s really laughing.

FRANS DE WAAL: Yeah, yeah, yeah.

IRA FLATOW: And all these different animals, and horses and things like that.

FRANS DE WAAL: Well, the reaction is, of course, of the general public is obviously, they don’t– they assume emotions in animals, even though the animals that we eat, they often don’t talk about. But anyway, the animals that we keep, they would say.

But in science, of course, there has been an extreme reluctance. And even though I have always worked on, let’s say, conflict resolution and reconciliation and that kind of things or empathy, where emotions clearly play a role, even there, the word “emotion” is often not used for animals because we I think we confuse emotions with feelings. And people wanted to stay away from that.

IRA FLATOW: You write in the book that you’ve always been fascinated with observing others, even from an early age. So what led you toward primatology particularly?

FRANS DE WAAL: That’s almost like an accident. As a child, I collected all sorts of water animals because Holland is full of water, and so salamanders, fish. I also collected birds and mice and frogs and all that kind of things.

And then when I went to the university, I wanted to study animals. And I became a biologist. But in my first university that I went to, they only worked with dead animals that you cut open. And I found that extremely boring. So I went to another university, where they did animal studies, ethology. And that’s how I rolled into animal behavior.

And the primate work is almost like an accident. I could have ended up with fish or with birds or whatever. I love animals. And so for me, it doesn’t make so much of a difference. But if you want to make comparisons with humans, of course, then the primates are ideal.

IRA FLATOW: You go through so many different emotions. I mean, you talk about bereavement. You talk about funerals that the chimps have for each other. I mean, tell us about some of the more interesting ones that you’ve discovered.

FRANS DE WAAL: Yeah, so one of the emotions I went through is disgust because psychologists have recently declared disgust a uniquely human emotion, maybe based on moral disgust, when we are disgusted by the behavior, let’s say, by people who get their kids into schools by illegal means, for example. So we’re disgusted by the kind of things. And so they have declared disgust uniquely human.

But disgust is a very old emotion that serves to keep contaminants and parasites out of your body. And we see it in many species.

IRA FLATOW: How does it manifest itself?

FRANS DE WAAL: So, for example, dogs are often said to be lacking in disgust because they lick their testicles, and they eat feces and stuff like that. And people use them as an example. But dogs are very disgusted by citrus, for example. If you cut open a lemon and you hold it– you shouldn’t feed it to your dog because it’s actually poisonous to them. But you hold it in front of them, they will show a full-blown disgust response. Chimpanzees in disgust displays, they have a face very similar to the human disgust face, where we curl up the lip and bring the lip close, the upper lip close to the nose.

IRA FLATOW: And you also talk about chimps caring for each other when they’re ill. And they bring blankets for the dead. And who would have thought that? You would have.

FRANS DE WAAL: Yeah, yeah. So we had a male at [INAUDIBLE] who was dying. And we kept him apart. And we kept the door a little bit open so that the others could access him. And he was in a very bad shape. And the females would actually bring straw to him and shove it behind his back. He was leaning against the wall, the way we do when we go to a hospital and put pillows behind people.

IRA FLATOW: Because you study chimps and you find these emotions and behaviors that other people would not have found, do you think that we are misinterpreting the intelligence and possibly the emotions of Neanderthals?

FRANS DE WAAL: Oh, I’m sure. The Neanderthals have been downplayed by our species for ages. The Neanderthals must be stupid and backward and so on.

I think all the evidence that we see is that that’s not the case. The Neanderthals actually had brains slightly larger than our brain. And so I think we have totally underestimated the Neanderthals.

IRA FLATOW: You mentioned in your book how many so-called animalistic things humans do without realizing that we do it. I’ll give you an example, sniffing our hand after we shake hands with somebody.

FRANS DE WAAL: Yeah, they found that on hidden cameras. They had filmed a lot of people greeting each other. And they found that when people greet someone by shaking hands of the same gender, they tend to bring their hand to their nose. And they probably not even aware that they’re sniffing the other one, but they’re doing that.

IRA FLATOW: A tweet coming in. What research is there regarding the response to music in animals? What, if any, music appears to generate or reflect mood?

FRANS DE WAAL: Well, there is research now on that increasingly. For example, whether animals can follow the rhythm of music or follow the rhythm that you as a human present them with. And some animals are actually quite good at that, like parrots are good at it and pinnipeds, like the sea lions are good at it.

We also did experiments where we present music to apes and see what they like and what they don’t like. We found, I believe, that Indian music was really liked by chimpanzees. So people do experiments on this. Whether they experience emotions similar to the ones that we experience with music is hard to tell. All we can measure is, do they want to listen to it or not want to listen to it?

One of the funniest ones was a very old experiment on starlings in a cage, which could hop from one perch to another one. And one perch produced Mozart, and the other one produced Schoenberg. And the starlings clearly preferred Mozart, as you might expect.

IRA FLATOW: So you can’t tell if certain music is soothing or if certain music is excitatory?

FRANS DE WAAL: No. Yeah, maybe there are ways of telling that apart. But for the moment, we just look at preferences.

IRA FLATOW: All right, let’s go to the phones, to Matthew in Denver. Hi, Matthew.

AUDIENCE: Hi. I was wondering, Frans, how you’ve seen the veterinary world change with regards to animal emotions being more accepted and maybe primates used in research.

FRANS DE WAAL: Well, I think the veterinary schools, they need to do more on behavior. They very often ignore behavior. I know some that have behavior classes for the students. But they very often ignore the behavior of animals. And that includes also the emotions and the expression of emotions.

As far as primates in research, you know probably that in chimpanzees, that is sort of ended. Chimpanzees are not really used for biomedical studies anymore. And the other primates that are being kept, like macaques are still kept in many facilities, I think should all be housed socially. My view has always been that you cannot keep these monkeys in single cages, as they often still do. And I don’t know why they still do that because it’s really not necessary. And they can keep them in social groups. And that would be so far better than what they do at the moment.

IRA FLATOW: This is Science Friday from WNYC Studios, talking with Frans de Waal, author of Mama’s Last Hug– Animal Emotions and What They Tell Us About Ourselves. A tweet in from Susan, who says, “Cats have been recognized often as aloof and uninterested in humans. Owners may disagree. Discuss.”

FRANS DE WAAL: [LAUGHS] I happen to be an owner. I’ve had cats all my life. And I think cats are just very variable. There are cats who are loners. Yes, they exist.

But there’s also many cats who are very social. I always used to have four cats. If you move from one room in the house to the other room in the house, all the cats would move to the room where you are because they I think they like variation, and they like your presence. And actually, cats are much more sociable than people often assume.

IRA FLATOW: You write that the emotional lives of birds are on par with mammals. Tell us about that.

FRANS DE WAAL: Yeah, birds have these very strong attachments. So, for example, if you talk about grieving and being affected by the death of a partner, then birds are a prime example because many birds have lifelong bonds between male and female. And so if one of them dies– I used to have jackdaws, which is a sort of corvid, little crow, actually. And I had two that were very bonded to each other.

And when the female disappeared, she escaped from the voliere, the male kept calling and calling and calling until he died, basically. He didn’t eat. And he died.

IRA FLATOW: Is that right?

FRANS DE WAAL: Yeah.

IRA FLATOW: Yeah. And you also talk about rodent faces were long thought to be unaffected by emotions. But detailed studies show other rodents have no problem recognizing–

FRANS DE WAAL: No, the rodent literature will always emphasize that they have no facial expressions. And now recently there was a study, for example, in Switzerland that was done, where they– that was a funny study. They had two classes of rats, one that they tickled and treated very well, and they made them very happy, and another group that they didn’t do much with. And then they asked an independent judge to judge from the face and the color of the ears what they thought had happened. And they could tell the happy rodents apart from the unhappy ones.

IRA FLATOW: In the last few minutes, tell us what the emotions tell us about ourselves. How would you summarize that?

FRANS DE WAAL: I think we are much more emotional beings than we often say we are. We think we are rational beings. And we take all these rational decisions. But I think emotions figure into everything we do.

And we also underestimate the animality of our emotions because I don’t think we have emotions that animals don’t have. So basically, I look at our emotions like organs. I don’t have any organ in my body that a frog doesn’t have or a rat doesn’t have. I have a liver and a kidney and a heart and brain and so on. And I think the same is true for our emotions. There are no human emotions in my mind that cannot be traced back to equivalent animal emotions.

IRA FLATOW: In fact, you talk about in your book that pigs can have an optimistic or pessimistic look, depending on how they’re raised.

FRANS DE WAAL: Yeah, yeah, they have done experiments on pigs because they do these experiments where they have to react to an ambivalent stimulus and see if they’re hoping for food or not hoping for food. And so you can you can test the optimism of the pig. And the optimism of the pig depends on how the pig is kept. If the pig is kept in a nice space with a lot of straw and enrichment, the pig is more optimistic than the ones who are kept in a barren place.

IRA FLATOW: Mhm. So let’s not confuse when we talk about animals what we think animal intelligence is and emotion is, right?

FRANS DE WAAL: Yeah. I think some animals are maybe not the most intelligent animals, but they are very emotional. But I think all animals, all the mammals, for sure, and also all the birds, they have quite an emotionality.

IRA FLATOW: Indeed, do animals have comedy, laughter?

FRANS DE WAAL: Yeah, actually, I describe some examples of the sense of humor of the great apes. And so, for example, one example is this was a fellow researcher of mine who put on a panther mask and hid in the bushes away from the chimpanzees. And then all of a sudden, he showed himself. And all the chimps, 25 chimps, they got very angry at him and started throwing stuff at him. And he did that multiple times.

And then at some point, he took the mask off, showing his own human face. And there were many chimps who had this laugh expression that chimpanzees have, as if they thought this was amusing, that he had been tricking them.

IRA FLATOW: What don’t you know yet that you want to know?

FRANS DE WAAL: Oh, I want to know more about the feeling side of the emotions, about how they experience them. So we don’t know that, really. And for the moment, that’s why in my book I’m very shy about the feeling part of the emotions. But I think with neuroscience, we may get there. And we can maybe see if the feelings associated with them are similar to ours.

IRA FLATOW: That’s primatologist Frans de Waal talking to me in 2019. We were discussing his book, Mama’s Last Hug– Animal Emotions and What They Tell Us About Ourselves. You can read an excerpt at sciencefriday.com/lasthug. Frans de Waal passed away last week at the age of 75.

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