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Skeptic: How can we know what another mind is thinking or feeling?

Frans de Waal: My work is on animals that cannot talk, which is both a disadvantage and advantage. It’s a disadvantage because I cannot ask them how they feel and what their experiences are, but it is an advantage because I think humans lie a lot. I don’t trust humans. I’m a biologist but I work in a psychology department, and all my colleagues are psychologists. Most psychologists nowadays use questionnaires, and they trust what people tell them, but I don’t. So, I’d much rather work with animals where instead of asking how often they have sex, I just count how often. That’s more reliable.

That said, I distinguish between emotions and feelings because you cannot know the feelings of any animals. But I can deduce them, guess at them. Personally, I feel it’s very similar with humans. Humans can tell me their feelings, but even if you tell me that you are sad, I don’t know if that’s the same sadness that I would feel under the same circumstances, so I can only guess what you feel. You might even be experiencing mixed feelings, or there may be feelings you’re not even aware of, and so you’re not able to communicate them. We have the same problem in non-human species as we do in humans, because feelings are less accessible and require guesswork.

That said, sometimes I’m perfectly comfortable guessing at the feelings of animals, even though you must distinguish them from the things you can measure. I can measure facial expressions. I can measure blood pressure. I can measure their behavior, but I can never really measure what they feel. But then, psychologists can’t do that with people either.

Skeptic: Suppose I’m feeling sad and I’m crying at some sort of loss. And then I see you’ve experienced a loss and that you’re crying … Isn’t it reasonable to infer that you feel sad?

FdW: Yes. And so that same principle of being reasonable can be applied to other species. And the closer that species is to you, the easier it is. Chimpanzees and bonobos cry and laugh. They have facial expressions— the same sort of expressions we do. So it’s fairly easy to infer the feelings behind those expressions and infer they may be very similar to our own. If you move to, say, an elephant, which is still a mammal, or to a fish, which is not, it becomes successively more difficult. Fish don’t even have facial expressions. That doesn’t mean that fish don’t feel anything. It would be a very biased view to assume that an animal needs to show facial expressions as evidence that it feels something.

At the same time, research on humans has argued that we have six basic emotions based on the observation that we have six basic facial expressions. So, there the tie between emotions and expressions has been made very explicit.

In my work, I tend to focus on the expressive behavior. But behind it, of course, there must be similar feelings. At least that’s what Darwin thought.

Skeptic: That’s not widely known, is it? Darwin published The Expression of the Emotions in Man and Animals in 1872, but it took almost a century before the taboo against it started to lift.

FdW: It’s the only book of Darwin’s that disappeared from view for a century. All the other books were celebrated, but that book was placed under some sort of taboo. Partly because of the influence of the behaviorist school of B.F. Skinner, Richard Herrnstein, and others, it was considered silly to think that animals would have the same sort of emotions as we do.

Biologists, including my own biology professors, however, found a way out. They didn’t need to talk about emotions because they would talk about the function of behavior. For example, they would not say “the animal is afraid” but rather that “the animal escapes from danger.” They phrased everything in functional terms—a semantic trick that researchers still often use.

If you were to say that two animals “love each other” or that “they’re very attached to each other,” you’re likely to receive significant criticism, if not ridicule. So why even describe it that way? Instead, you objectively report that the animals bonded and they benefited from doing so. Phrasing it functionally has, well, functioned as a sort of preferred safe procedure. But I have decided not to employ it anymore.

Skeptic: In most of your books you talk about the social and political context of science. Why do you think the conversation about animal emotions was held back for almost a century?

FdW: World War II had an effect on the study of aggression, which became a very popular topic in the 1960s and 70s. Then we got the era of “the selfish gene” and so on. In fact, the silencing of the study of mental processes and emotions in animals started before the war. It actually started in the 1920s and 30s. And I think it’s because scientists such as Skinner wanted the behavioral sciences to be like the physical sciences. They operated under the belief that it provided a certain protection against criticism to get away from anything that could be seen as speculation. And there was a lot of speculation going on in the so-called “depth psychologies,” some of it rather wild.

However, there are a lot of invisible things in science that we assume to be true, for example, evolutionary theory. Evolution is not necessarily visible, at least most of the time it isn’t, yet still, we believe very strongly that evolution happened. Continental drift is unobservable, but we now accept that it happened. The same principle can be applied to animal feelings and animal consciousness. You assume it as a sort of theory and see if things fit. And, research has demonstrated that things fit quite well.

Skeptic: Taking a different angle, can Artificial Intelligence (AI) experience emotions? Was IBM’s Watson “thrilled” when it beat Ken Jennings, the all-time champion of Jeopardy!? Well, of course not. So what do you think about programming such internal states into an artificial intelligence?

FdW: I think researchers developing AI models are interested in affective programs because of the way we biologists look at emotions. Emotions trigger actions that are adaptive. Fear is an adaptive emotion because it may trigger certain behaviors such as hiding, escaping, etc., so we look at emotions as being the stimulus that elicits certain specific types of behavior. Emotions organize behavior, and I think that’s what the AI people are interested in. Emotions are actually a very smart system, compared to instincts. Someone might argue that instincts also trigger behavior. However, while instincts are inflexible, emotions are different.

Let’s say you are afraid of something. The emotion of fear doesn’t trigger your behavior. An emotion just prepares the body for certain behaviors, but you still need to make a decision. Do I want to escape? Do I want to fight? Do I want to hide? What is the best behavior under these circumstances? And so, your emotion triggers the need for a response, and then your cognition takes over and searches for the best solution. It’s a very, very nice system and creators of AI models are interested in such an organizational system of behavior. I’m not sure they will ever construct the feelings behind the emotions—it’s not an easy thing to do—but certainly organizing behavior according to emotions is possible.

Skeptic: Are emotions created from the bottom-up? How do you scale from something very simple up to much higher levels of complexity?

FdW: Humans have a complex emotional system—we mix a lot of emotions, sort them, regulate them. Well, sometimes we don’t actually regulate them and that is something that really interests me in my work with animals. What kind of regulation do they have over their emotions? People often say that we have emotions and we can suppress them, whereas animals have emotions that they have to follow. However, experiments have demonstrated that’s not really the case. For example, we give apes the marshmallow test. Briefly, that’s where you put a child in a situation in which he or she can either eat a marshmallow immediately, or wait and get a second one later. Well, kids are willing to wait for 15 minutes. If you do that same experiment with apes, they’re also willing to wait for 15 minutes. So they can control their emotions. And like children, apes seek distractions from the situation because they’re aware that they’re dealing with certain specific emotions. Therefore, we know that apes have a certain awareness of their emotions, and they have a certain level of control over them. This whole idea that regulation of emotions is specifically human, while animals can only follow them, is wrong.

That’s actually the reason I wrote Mama’s Last Hug. The starting point of the book was when Prof. Jan Van Hoff came on TV and showed a little clip that everyone has seen by now, where he and a chimpanzee called Mama hug each other. Both he and I were shocked when the clip went viral and generated such a response. Many people cried and wrote to us to say they were very influenced by what they saw. The truth is Mama was simply showing perfectly normal chimpanzee behavior. It was a very touching moment, obviously, but for those familiar with chimps, there was nothing surprising about the behavior. And so, I wrote this book partly because I noticed that people did not know how human-like the expressions of the apes are. Embracing, and hugging, and calming someone down, and having a big smile on your face are all common behaviors seen in primates and are not unique to humans.

Skeptic: Your famous experiment with capuchin monkeys, where you offer them a grape or a piece of cucumber, is along similar lines. When the monkey got the cucumber instead of the grape, he got really angry. He threw the cucumber back, then proceeded to pound on the table and the walls … He was clearly ticked off at the injustice he felt had been done him, just as a person would be.

FdW: The funny thing is that primates, including those monkeys, have all the same expressions and behaviors as we do. And so, they shake their cage and throw the cucumber at you. The behavior is just so extremely similar, and the circumstances are so similar … I always say that if related species behave in a similar way under similar circumstances, you have to assume a shared psychology lies behind it. It is just not acceptable in this day and age of Darwinian philosophy, so to speak, to assume anything else. If people want to make the point that it’s maybe not similar, that maybe the monkey was actually very happy while he was throwing the stuff … they’ll have a lot of work to do to convince me of that.

Skeptic: What’s the date of the last common ancestor humans shared with chimps and bonobos?

FdW: It’s about 6 million years ago.

Skeptic: So, these are indeed pretty ancient emotions.

FdW: Oh, they go back much further than that! Like the bonding mechanism based on oxytocin—the neuropeptides in bonding go back to rodents, and probably even back to fish at some point. These neuropeptide circuits involved in attachment and bonding are very ancient. They’re even older than mammals themselves.

Skeptic: One emotion that seems very uniquely human is disgust. If a chimp or Bonobo comes across a pile of feces or vomit, what do they do?

FdW: When we do experiments and put interesting food on top of feces and see if the chimp is willing to take it, they don’t. They refuse to. The facial expression of the chimps is the same as we have for disgust—with the wrinkly nose and all that. Chimps also show it, for example, when it rains. They don’t like rain. And they show it, sometimes, in circumstances where they encounter a rat. So, some of these emotions have been proposed as being uniquely human, but I disagree. Disgust, I think, is a very old emotion.

Disgust is an interesting case because we know that both in chimps and humans a specific part of the brain called the insula is involved. If you stimulate the insula in a monkey who’s chewing on good fruit, he’ll spit it out. If you put humans in a brain scanner and show them piles of feces or things they don’t want to see, the insula is likewise activated. So here we have an emotion that is triggered under the same circumstances, that is shown in the face in the same way, and that is associated with the same specific area in the brain. So we have to assume it’s the same emotion across the board. That’s why I disagree with those scientists who have declared disgust uniquely human.

Skeptic: In one of your lectures, you show photos of a horse wrinkling up its nose and baring its teeth. Is that a smile or something else?

FdW: The baring of the teeth is very complex because in many primates it is a fearful signal shown when they’re afraid or when they’re intimidated by dominance and showing submission. So, we think it became a signal of appeasement and non-hostility. Basically saying, “I’m not hostile. Don’t expect any trouble from me.” And then over time, especially in apes and then in humans, it became more and more of a friendly signal. So it’s not necessarily a fear signal. Although we still say that if someone smiles too much, they’re probably nervous.

Skeptic: Is it true that you can determine whether someone’s giving you a fake smile or a real smile depending on whether the corners of their eyes are pulled down?

FdW: Yes, this is called the Duchenne smile. Duchenne was a 19^th century French neurologist. He studied people who had facial paralysis, meaning they had the muscles, but they could not feel anything in their face. This allowed him to put electrodes on their faces and stimulate them. He methodically contracted different muscles and noticed he could produce a smile on his subjects. Yet he was never quite happy with the smile—it just didn’t look real. Then one day he told a subject a joke. A very good joke, I suppose, and all of a sudden, he got a real full-blown smile. That’s when Duchenne decided that there needs to be a contraction and a narrowing of the eyes for a smile to be a real smile. So, we now distinguish between the fake smile and the Duchenne smile.

Skeptic: So, smiling involves a whole complex suite of muscles. Is the number of muscles in the face of humans higher than other species?

FdW: Do we have far more muscles in the face than a chimpanzee? I’ve heard that all my life. Until people who analyze faces of chimpanzees found exactly the same number of muscles in there as in a human face. So that whole story doesn’t hold up. I think the confusion originated because when we look at the human face, we can interpret so many little details of it—and I think chimps do that with each other too—but when we look at a chimp, we only see the bold, more flamboyant expressions.

Skeptic: Have we evolved in the way we treat other animals?

FdW: The Planet of the Apes movies provide a good example of that. I’m so happy that Hollywood has found a way of featuring apes in movies without the involvement of real animals. There was a time when Hollywood had trainers who described what they do as affective training. Not effective, but affective. They used cattle prods, and stuff like that. People used to think that seeing apes dressed up or producing silly grins was hilarious. No longer. We’ve come a long way from that.

Skeptic: The Planet of the Apes films show apes that are quite violent, maybe even brutal. You actually studied the darker side of emotion in apes. Can you describe it?

This article appeared in Skeptic magazine 29.3
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FdW: Most of the books on emotions in animals dwell on the positive: they show how animals love each other, how they hug each other, how they help each other, how they grieve … and I do think that’s all very impressive. However, the emotional life of animals—just like that of humans— includes a lot of nasty emotions.

I have seen so much of chimpanzee politics that I witnessed those very dark emotions. They can kill each other. One of the killings I’ve witnessed was in captivity. So, when it happened, I thought maybe it was a product of captivity. Some colleagues said to me, “What do you expect if you lock them up?” But now we know that wild chimpanzees do the exact same thing. Sometimes, if a male leader loses his position or other chimps are not happy with him, they will brutally kill him. At the same time, chimpanzees can also be good friends, help each other, and defend their territory together—just like people who on occasion hate each other or even kill each other, but otherwise coexist peacefully.

The more important point is that we do not treat animals very well, certainly not in the agricultural industry. And we need to do something about that.

Skeptic: Are you a vegetarian or vegan?

FdW: No. Well, I do try to avoid eating meat. For me, however, the issue is not so much the eating, it’s the treatment of animals. As a biologist, I see the cycle of life as a natural thing. But it bothers me how we treat animals.

Skeptic: What’s next for you?

FdW: I’m going to retire! In fact, I’ve already stopped my research. I’m going to travel with my wife, and write.