In his new book, Frans de Waal draws on his renowned studies of the social and emotional lives of chimpanzees, bonobos and other primates, to illustrate how profoundly we have underestimated animals’ emotional experiences. He argues that emotions occupy a far more significant place in the way we organise our societies than a more rationalist approach would advocate.

Watching behaviour comes naturally to me, so much so that I may be overdoing it. I didn’t realise this until I came home one day to tell my mother about a scene on a regional bus. I must have been twelve. A boy and girl had been kissing in the gross way that I couldn’t relate to but that is typical of teenagers, with open mouths moistly clamped onto each other. This by itself was nothing special, but then I noticed the girl afterward chewing gum, whereas before the kiss I had seen only the boy chewing. I was puzzled but figured it out – ​it was like the law of communicating vessels. When I told my mom, however, she was less than thrilled. With a troubled expression, she told me to stop paying such close attention to people, saying it was not a very nice thing to do.

Observation is now my profession. But don’t expect me to notice the colour of a dress or whether a man wears a hairpiece – ​those things don’t interest me in the least. Instead, I focus on emotional expressions, body language, and social dynamics. These are so similar between humans and other primates that my skill applies equally to both, although my work mostly concerns the latter. As a student, I had an office overlooking a zoo colony of chimpanzees, and as a scientist at the Yerkes National Primate Research Center, near Atlanta, Georgia, I have had a similar situation for the last twenty-​five years. My chimps live outdoors at a field station and occasionally get into upheavals that cause such a ruckus that we rush to the window to take in the spectacle. What most people will see as a chaotic melee of twenty hairy beasts running about hollering and screaming is in fact a highly ordered society. We recognize every ape by face, even just by voice, and know what to expect. Without pattern recognition, observation remains unfocused and random. It would be like watching a sport that you’ve never played and don’t know much about. You basically see nothing. This is why I can’t stand American television coverage of international soccer matches: most sports narrators came late to the game and fail to grasp its fundamental strategies. They have eyes for the ball only and keep on blabbing during the most pivotal moments. This is what happens when we lack pattern recognition.

Looking beyond the central scene is key. If one male chimpanzee intimidates another by throwing rocks or charging closely past the other, you need to deliberately take your eyes off them to check the periphery, where new developments arise. I call it holistic observation: considering the wider context. That the threatened male’s best buddy is asleep in a corner doesn’t mean we can ignore him. As soon as he wakes up and walks toward the scene, the whole colony knows things are about to change. A female gives a loud hoot to announce the move, while mothers press their youngest offspring close.

And after the commotion has died down, you don’t just turn away. You keep your eyes on the main actors – ​they aren’t finished yet. Of the thousands of reconciliations I’ve witnessed, one of the first took me by surprise. Shortly after a confrontation, two male rivals walked upright, on two legs, toward each other, fully pilo-​erect – ​meaning their hair was standing on end, making them look twice their regular size. Their eye contact looked so fierce, I expected a revival of the hostilities. But when they got close to each other, one of them suddenly turned around and presented his behind. The other responded by grooming closely around the anus of the first male, uttering loud lip-​smacks and tooth-​clacks to indicate his dedication to the task. Since the first male wanted to do the same, they ended up in an awkward 69 position, which allowed each of them to groom the other’s behind at the same time. Soon thereafter they relaxed and turned around to groom each other’s faces. Peace was restored.

The initial grooming location may seem odd, but remember that English (as well as many other languages) has expressions such as brown-​nosing and ass-​licking. I’m sure there is a good reason. Among humans, intense fear may cause vomiting and diarrhea – ​we say we ‘crap our pants’ when we’re frightened. That’s also a common occurrence in apes, minus the pants. Bodily exits yield critical information. Long after a skirmish has ended, you may see a male chimpanzee casually stroll to the precise location in the grass where his rival had been sitting, only to bend down and take a sniff. Although vision is about as dominant a sense in chimpanzees as it is in us, smell remains critically important. In our species, too, as covert filming has demonstrated, after we shake hands with another person, especially someone of the same sex, we often scent our own hand. We lift it casually close to our face to gather a chemical whiff that informs us about the other’s disposition. We do so unconsciously, as we do so many things that resemble the behaviour of other primates. Nevertheless, we like to see ourselves as rational actors who know what we’re doing, while we depict other species as automatons. It’s really not that simple.

We are constantly in touch with our feelings, but the tricky part is that our emotions and our feelings are not the same. We tend to conflate them, but feelings are internal subjective states that, strictly speaking, are known only to those who have them. I know my own feelings, but I don’t know yours, except for what you tell me about them. We communicate about our feelings by language. Emotions, on the other hand, are bodily and mental states – from anger and fear to sexual desire and affection and seeking the upper hand – ​that drive behaviour. Triggered by certain stimuli and accompanied by behavioural changes, emotions are detectable on the outside in facial expression, skin colour, vocal timbre, gestures, odour, and so on. Only when the person experiencing these changes becomes aware of them do they become feelings, which are conscious experiences. We show our emotions, but we talk about our feelings.

Take reconciliation, or a friendly reunion following a confrontation. Reconciliation is a measurable emotional interaction: to detect it, all you, as an observer, need is some patience to see what happens between former antagonists. But the feelings that accompany a reconciliation – ​contrition, forgiveness, relief – ​are knowable only to those who experience them. You may suspect that others have the same feelings as you, but you can’t be sure even with respect to members of your own species. Someone may claim they have forgiven another person, for example, but can we trust this information? All too often, despite what they have told us, they bring up the affront in question on the first occasion that arises. We know our own inner states imperfectly and often mislead both ourselves and those around us. We’re masters of fake happiness, suppressed fear, and misguided love. This is why I’m pleased to work with non-linguistic creatures. I’m forced to guess their feelings, but at least they never lead me astray by what they tell me about themselves.

The study of human psychology usually relies on the use of questionnaires, which are heavy on self-​reported feelings and light on actual behaviour. But I favour the reverse. We need more observations of actual human social affairs. As a simple example, let me take you to a large conference in Italy, which I attended many years ago as a budding scientist. Being there to speak about how primates resolve conflicts, I hadn’t expected to see a perfect human example on display. A certain scientist was acting up in a way that I had never seen before and rarely have since. It must have been the combination of him being famous and being a native English speaker. At international meetings, Americans and Brits often mistake the extraordinary privilege of being able to speak in their mother tongue for intellectual superiority. Because no one is going to disagree with them in broken English, they are rarely disabused of this notion.

There was a whole program of lectures, and after every one, our famous English-​speaking scientist jumped out of his seat in the front row to help us understand the work. Just as one Italian speaker finished presenting her work, for example, and even as the applause for her lingered, this scientist rose from his seat, climbed to the podium, took the speaker’s mike, and literally said, ‘What she actually meant to say . . .’ I don’t remember the topic anymore, but the Italian speaker pulled a face. It was hard to miss this man’s cockiness and disrespect for her – ​nowadays we’d call it ‘mansplaining.’

Most of the audience members had been listening through a translation service – ​in fact, their delayed linguistic connection may have helped them see through his behaviour, in the same way that we’re better at reading body language in a televised debate when the sound is turned off. They began to hiss and boo.

The expression of surprise on the face of our famous scientist showed how much he had misjudged the reception of his power grab. Until then, he’d thought it was going swimmingly. Flustered and perhaps humiliated, he hastily stepped down from the podium.

I kept my eyes on him and on the Italian speaker as they sat in the audience. Within fifteen minutes, he approached her and offered her his translation device, since she didn’t have one. She politely accepted (perhaps without actually needing one), which counts as an implicit peace offer. I say ‘implicit’ because there were no signs that they mentioned the previous awkward moment. Humans often signal good intentions after a confrontation (a smile, a compliment) and leave it at that. I couldn’t follow what they were saying, but a third party told me that after all lectures were over, the scientist approached the speaker a second time and literally told her, ‘I have made a complete ass of myself.’ This admirable bit of self-​knowledge came close to an explicit reconciliation.