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5THE MEASURE OF ALL THINGS

Ayumu had no time for me while he was working on his computer. He lives with other chimps in an outdoor area at the Primate Research Institute (PRI) of Kyoto University. At any moment, an ape can run into one of several cubicles—like little phone booths—equipped with a computer. The chimp can also leave the cubicle whenever he wants. This way playing computer games is entirely up to them, which guarantees sound motivation. Since the cubicles are transparent and low, I could lean on one to look over Ayumu’s shoulder. I watched his incredibly rapid decision making the way I admire my students typing ten times faster than me.

Ayumu, is a young male who, in 2007, put human memory to shame. Trained on a touchscreen, he can recall a series of numbers from 1 through 9 and tap them in the right order, even though the numbers appear randomly on the screen and are replaced by white squares as soon as he starts tapping. Having memorized the numbers, Ayumu touches the squares in the correct order. Reducing the amount of time the numbers flash on the screen doesn’t seem to matter to Ayumu, even though humans become less accurate the shorter the time interval. Trying the task myself, I was unable to keep track of more than five numbers after staring at the screen for many seconds, while Ayumu can do the same after seeing the numbers for just 210 milliseconds. This is one-fifth of a second, literally the bat of an eye. One follow-up study managed to train humans up to Ayumu’s level with five numbers, but the ape remembers up to nine with 80 percent accuracy, something no human has managed so far.1 Taking on a British memory champion known for his ability to memorize an entire stack of cards, Ayumu emerged the “chimpion.”

Ayumu’s photographic memory allows him to quickly tap a series of numbers on a touchscreen in the right order, even though the numbers disappear in the blink of an eye. That humans cannot keep up with this young ape has upset some psychologists.

The distress Ayumu’s photographic memory caused in the scientific community was of the same order as when, half a century ago, DNA studies revealed that humans barely differ enough from bonobos and chimpanzees to deserve their own genus. It is only for historical reasons that taxonomists have let us keep the Homo genus all to ourselves. The DNA comparison caused hand-wringing in anthropology departments, where until then skulls and bones had ruled supremely as the gauge of relatedness. To determine what is important in a skeleton takes judgment, though, which allows the subjective coloring of traits that we deem crucial. We make a big deal of our bipedal locomotion, for example, while ignoring the many animals, from chickens to hopping kangaroos, that move the same way. At some savanna sites, bonobos walk entire distances upright through tall grass, making confident strides like humans.2 Bipedalism is really not as special as it has been made out to be. The good thing about DNA is that it is immune to prejudice, making it a more objective measure.

With regard to Ayumu, however, it was the turn of psychology departments to be upset. Since Ayumu is now training on a much larger set of numbers, and his photographic memory is being tried on ever shorter time intervals, the limits of what he can do are as yet unknown. But this ape has already violated the dictum that, without exception, tests of intelligence ought to confirm human superiority. As expressed by David Premack, “Humans command all cognitive abilities, and all of them are domain general, whereas animals, by contrast, command very few abilities, and all of them are adaptations restricted to a single goal or activity.”3 Humans, in other words, are a singular bright light in the dark intellectual firmament that is the rest of nature. Other species are conveniently swept together as “animals” or “the animal”—not to mention “the brute” or “the nonhuman”—as if there were no point differentiating among them. It is an us-versus-them world. As the American primatologist Marc Hauser, inventor of the term humaniqueness, once said: “My guess is that we will eventually come to see that the gap between human and animal cognition, even a chimpanzee, is greater than the gap between a chimp and a beetle.”4

You read it right: an insect with a brain too small for the naked eye is put on a par with a primate with a central nervous system that, albeit smaller than ours, is identical in every detail. Our brain is almost exactly like an ape’s, from its various regions, nerves, and neurotransmitters to its ventricles and blood supply. From an evolutionary perspective, Hauser’s statement is mind-boggling. There can be only one outlier in this particular trio of species: the beetle.

Evolution Stops at the Human Head

Given that the discontinuity stance is essentially pre-evolutionary, let me call a spade a spade, and dub it Neo-Creationism. Neo-Creationism is not to be confused with Intelligent Design, which is merely old creationism in a new bottle. Neo-Creationism is subtler in that it accepts evolution but only half of it. Its central tenet is that we descend from the apes in body but not in mind. Without saying so explicitly, it assumes that evolution stopped at the human head. This idea remains prevalent in much of the social sciences, philosophy, and the humanities. It views our mind as so original that there is no point comparing it to other minds except to confirm its exceptional status. Why care about what other species can do if there is literally no comparison with what we do? This saltatory view (from saltus, or “leap”) rests on the conviction that something major must have happened after we split off from the apes: an abrupt change in the last few million years or perhaps even more recently. While this miraculous event remains shrouded in mystery, it is honored with an exclusive term—hominization—mentioned in one breath with words such as spark, gap, and chasm.5 Obviously, no modern scholar would dare mention a divine spark, let alone special creation, but the religious background of this position is hard to deny.

In biology, the evolution-stops-at-the-head notion is known as Wallace’s Problem. Alfred Russel Wallace was a great English naturalist who lived at the same time as Charles Darwin and is considered the coconceiver of evolution by means of natural selection. In fact, this idea is also known as the Darwin-Wallace Theory. Whereas Wallace definitely had no trouble with the notion of evolution, he drew a line at the human mind. He was so impressed by what he called human dignity that he couldn’t stomach comparisons with apes. Darwin believed that all traits were utilitarian, being only as good as strictly necessary for survival, but Wallace felt there must be one exception to this rule: the human mind. Why would people who live simple lives need a brain capable of composing symphonies or doing math? “Natural selection,” he wrote, “could only have endowed the savage with a brain a little superior to that of an ape, whereas he actually possesses one but very little inferior to that of the average member of our learned societies.”6 During his travels in Southeast Asia, Wallace had gained great respect for nonliterate people, so for him to call them only “very little inferior” was a big step up over the prevailing racist views of his time, according to which their intellect was halfway between that of an ape and Western man. Although he was nonreligious, Wallace attributed humanity’s surplus brain power to the “unseen universe of Spirit.” Nothing less could account for the human soul. Unsurprisingly, Darwin was deeply disturbed to see his respected colleague invoke the hand of God, in however camouflaged a way. There was absolutely no need for supernatural explanations, he felt. Nevertheless, Wallace’s Problem still looms large in academic circles eager to keep the human mind out of the clutches of biology.

I recently attended a lecture by a prominent philosopher who enthralled us with his take on consciousness, until he added, almost like an afterthought, that “obviously” humans possess infinitely more of it than any other species. I scratched my head—a sign of internal conflict in primates—because until then the philosopher had given the impression that he was looking for an evolutionary account. He had mentioned massive interconnectivity in the brain, saying that consciousness arises from the number and complexity of neural connections. I have heard similar accounts from robot experts, who feel that if enough microchips connect within a computer, consciousness is bound to emerge. I am willing to believe it, even though no one seems to know how interconnectivity produces consciousness nor even what consciousness exactly is.

The emphasis on neural connections, however, made me wonder what to do with animals with brains larger than our 1.35-kilogram brain. What about the dolphin’s 1.5-kilogram brain, the elephant’s 4-kilogram brain, and the sperm whale’s 8-kilogram brain? Are these animals perhaps more conscious than we are? Or does it depend on the number of neurons? In this regard, the picture is less clear. It was long thought that our brain contained more neurons than any other on the planet, regardless of its size, but we now know that the elephant brain has three times as many neurons—257 billion, to be exact. These neurons are differently distributed, though, with most of the elephant’s in its cerebellum. It has also been speculated that the pachyderm brain, being so huge, has many connections between far-flung areas, almost like an extra highway system, which adds complexity.7 In our own brain, we tend to emphasize the frontal lobes—hailed as the seat of rationality—but according to the latest anatomical reports, they are not truly exceptional. The human brain has been called a “linearly scaled-up primate brain,” meaning that no areas are disproportionally large.8 All in all, the neural differences seem insufficient for human uniqueness to be a foregone conclusion. If we ever find a way of measuring it, consciousness could well turn out to be widespread. But until then some of Darwin’s ideas will remain just a tad too dangerous.

This is not to deny that humans are special—in some ways we evidently are—but if this becomes the a priori assumption for every cognitive capacity under the sun, we are leaving the realm of science and entering that of belief. Being a biologist who teaches in a psychology department, I am used to the different ways disciplines approach this issue. In biology, neuroscience, and the medical sciences, continuity is the default assumption. It couldn’t be otherwise, because why would anyone study fear in the rat amygdala in order to treat human phobias if not for the premise that all mammalian brains are similar? Continuity across life-forms is taken for granted in these disciplines, and however important humans may be, they are a mere speck of dust in the larger picture of nature.

Increasingly, psychology is moving in the same direction, but in other social sciences and the humanities discontinuity remains the typical assumption. I am reminded of this every time I address these audiences. After a lecture that inevitably (even if I don’t always mention humans) reveals similarities between us and the other Hominoids, the question invariably arises: “But what then does it mean to be human?” The but opening is telling as it sweeps all the similarities aside in order to get to the all-important question of what sets us apart. I usually answer with the iceberg metaphor, according to which there is a vast mass of cognitive, emotional, and behavioral similarities between us and our primate kin. But there is also a tip containing a few dozen differences. The natural sciences try to come to grips with the whole iceberg, whereas the rest of academia is happy to stare at the tip.

In the West, fascination with this tip is old and unending. Our unique traits are invariably judged to be positive, noble even, although it wouldn’t be hard to come up with a few unflattering ones as well. We are always looking for the one big difference, whether it is opposable thumbs, cooperation, humor, pure altruism, sexual orgasm, language, or the anatomy of the larynx. It started perhaps with the debate between Plato and Diogenes about the most succinct definition of the human species. Plato proposed that humans were the only creatures at once naked and walking on two legs. This definition proved flawed, however, when Diogenes brought a plucked fowl to the lecture room, setting it loose with the words “Here is Plato’s man.” From then on the definition added “having broad nails.”

In 1784 Johann Wolfgang von Goethe triumphantly announced that he had discovered the biological roots of humanity: a tiny piece of bone in the human upper jaw known as the os intermaxillare. Though present in other mammals, including apes, the bone had never before been detected in our species and had therefore been labeled “primitive” by anatomists. Its absence in humans had been taken as something we should be proud of. Apart from being a poet, Goethe was a natural scientist, which is why he was delighted to link our species to the rest of nature by showing that we shared this ancient bone. That he did so a century before Darwin reveals how long the idea of evolution had been around.

The same tension between continuity and exceptionalism persists today, with claim after claim about how we differ, followed by the subsequent erosion of these claims.9 Like the os intermaxillare, uniqueness claims typically cycle through four stages: they are repeated over and over, they are challenged by new findings, they hobble toward retirement, and then they are dumped into an ignominious grave. I am always struck by their arbitrary nature. Coming out of nowhere, uniqueness claims draw lots of attention while everyone seems to forget that there was no issue before. For example, in the English language (and quite a few others), behavioral copying is denoted by a verb that refers to our closest relatives, hinting at a time when imitation was no big deal and was considered something we shared with the apes. But when imitation was redefined as cognitively complex, dubbed “true imitation,” all of a sudden we became the only ones capable of it. It made for the peculiar consensus that we are the only aping apes. Another example is theory of mind, a concept that in fact derives from primate research. At some point, however, it was redefined in such a manner that it seemed, at least for a while, absent in apes. All these definitions and redefinitions take me back to a character played by Jon Lovitz on Saturday Night Live, who conjured unlikely justifications of his own behavior. He kept digging and searching until he believed his own fabricated reasons, exclaiming with a self-satisfied smirk, “Yeah! That’s the ticket!”

With regard to technical skills, the same thing happened despite the fact that ancient gravures and paintings commonly depicted apes with a walking cane or some other instrument, most memorably in Carl Linnaeus’s Systema Natura in 1735. Ape tool use was well known and not the least bit controversial at the time. The artists probably put tools in the apes’ hands to make them look more humanlike, hence for exactly the opposite reason anthropologists in the twentieth century elevated tools to a sign of brainpower. From then on, the technology of apes was subjected to scrutiny and doubt, ridicule even, while ours was held up as proof of mental preeminence. It is against this backdrop that the discovery (or rediscovery) of ape tool use in the wild was so shocking. In their attempts to downplay its importance, I have heard anthropologists suggest that perhaps chimpanzees learned how to use tools from humans, as if this would be any more likely than having them develop tools on their own. This proposal obviously goes back to a time when imitation had not yet been declared uniquely human. It is hard to keep all those claims consistent. When Leakey suggested that we must either call chimpanzees human, redefine what it is to be human, or redefine tools, scientists predictably embraced the second option. Redefining man will never go out of fashion, and every new characterization will be greeted with “Yeah! That’s the ticket!”

Even more egregious than human chest beating—another primate pattern—is the tendency to disparage other species. Well, not just other species, because there is a long history of the Caucasian male declaring himself genetically superior to everyone else. Ethnic triumphalism is extended outside our species when we make fun of Neanderthals as brutes devoid of sophistication. We now know, however, that Neanderthal brains were slightly larger than ours, that some of their genes were absorbed into our own genome, and that they knew fire, burials, hand-axes, musical instruments, and so on. Perhaps our brothers will finally get some respect. When it comes to the apes, however, contempt persists. When in 2013 the BBC website asked Are You as Stupid as a Chimpanzee? I was curious to learn how they had pinpointed the level of chimpanzee intelligence. But the website (since removed) merely offered a test of human knowledge about world affairs, which had nothing to do with apes. The apes merely served to draw a contrast with our species. But why focus on apes in this regard rather than, say, grasshoppers or goldfish? The reason is, of course, that everyone is ready to believe that we are smarter than these animals, yet we are not entirely sure about species closer to us. It is out of insecurity that we love the contrast with other Hominoids, as is also reflected in angry book titles such as Not a Chimp or Just Another Ape?10

The same insecurity marked the reaction to Ayumu. People watching his videotaped performance on the Internet either did not believe it, saying it must be a hoax, or had comments such as “I can’t believe I am dumber than a chimp!” The whole experiment was taken as so offensive that American scientists felt they had to go into special training to beat the chimp. When Tetsuro Matsuzawa, the Japanese scientist who led the Ayumu project, first heard of this reaction, he put his head in his hands. In her charming behind-the-scenes look at the field of evolutionary cognition, Virginia Morrell recounts Matsuzawa’s reaction:

Really, I cannot believe this. With Ayumu, as you saw, we discovered that chimpanzees are better than humans at one type of memory test. It is something a chimpanzee can do immediately, and it is one thing—one thing—that they are better at than humans. I know this has upset people. And now there are researchers who have practiced to become as good as a chimpanzee. I really don’t understand this need for us to always be superior in all domains.11

Even though the iceberg’s tip has been melting for decades, attitudes barely seem to budge. Instead of discussing them any further here or going over the latest uniqueness claims, I will explore a few claims that are now close to retirement. They illustrate the methodology behind intelligence testing, which is crucial to what we find. How do you give a chimp—or an elephant or an octopus or a horse—an IQ test? It may sound like the setup to a joke, but it is actually one of the thorniest questions facing science. Human IQ may be controversial, especially while we are comparing cultural or ethnic groups, but when it comes to distinct species, the problems are a magnitude greater.

I am willing to believe a recent study that found cat lovers to be more intelligent than dog lovers, but this comparison is a piece of cake relative to one drawing a contrast between actual cats and dogs. Both species are so different that it would be hard to design an intelligence test that both of them perceive and approach similarly. At issue, however, is not just how two animal species compare but—the big gorilla in the room—how they compare to us. And in this regard, we often abandon all scrutiny. Just as science is critical of any new finding in animal cognition, it is often equally uncritical with regard to claims about our own intelligence. It swallows them hook, line, and sinker, especially if they—unlike Ayumu’s feat—are in the expected direction. In the meantime, the general public gets confused, because inevitably any such claims provoke studies that challenge them. Variation in outcome is often a matter of methodology, which may sound boring but goes to the heart of the question of whether we are smart enough to know how smart animals are.

Methodology is all we have as scientists, so we pay close attention to it. When our capuchin monkeys underperformed on a face-recognition task on a touchscreen, we kept staring at the data until we discovered that it was always on a particular day of the week that the monkeys fared so poorly. It turned out that one of our student volunteers, who carefully followed the script during testing, had a distracting presence. This student was fidgety and nervous, always changing her body postures or adjusting her hair, which apparently made the monkeys nervous, too. Performance improved dramatically once we removed this young woman from the project. Or take the recent finding that male but not female experimenters induce so much stress in mice that it affects their responses. Placing a T-shirt worn by a man in the room has the same effect, suggesting that olfaction is key.12 This means, of course, that mouse studies conducted by men may have different outcomes than those conducted by women. Methodological details matter much more than we tend to admit, which is particularly relevant when we compare species.

Knowing What Others Know

Imagine that aliens from a distant galaxy landed on earth wondering if there was one species unlike the rest. I am not convinced they would settle on us, but let’s assume they did. Do you think they’d do so based on the fact that we know what others know? Of all the skills that we possess and all the technology that we have invented, would they zoom in on the way we perceive one another? What an odd and capricious choice this would be! But it is precisely the trait that the scientific community has considered most worthy of attention for the last two decades. Known as theory of mind, abbreviated ToM, it is the capacity to grasp the mental states of others. And the profound irony is that our fascination with ToM did not even start with our species. Emil Menzel was the first to ponder what one individual knows about what others know, but he did so for juvenile chimpanzees.

In the late 1960s Menzel would take a young ape by the hand out into a large, grassy enclosure in Louisiana to show her hidden food or a scary object, such as a toy snake. After this, he would bring her back to the waiting group and release them all together. Would the others pick up on the knowledge of one among them, and if so, how would they react? Could they tell the difference between the other having seen food or a snake? They most certainly could, being eager to follow a chimp who knew a food location or being reluctant to stay with one who’d just seen a hidden snake. Copying the other’s enthusiasm or alarm, they had an inkling of his knowledge.13

Scenes around food were especially telling. If the “knower” ranked below the “guessers,” the former had every reason to conceal his or her information to keep the food out of the wrong hands. We recently repeated these experiments with our own chimps and found the same subterfuge as reported by Menzel. Katie Hall would remove two of our chimps from their outdoor enclosure and keep them temporarily in a building. Low-ranking Reinette would have a small window from which to look out into the enclosure, whereas high-ranking Georgia would have no such view. Katie would walk around hiding two food items: one entire banana and one entire cucumber. Guess which one chimps prefer! She’d stuff food underneath a rubber tire, in a hole in the ground, in the deep grass, behind a climbing pole, or some other place, while Reinette followed her every move from inside. Then we’d release both chimps at the same time. By then, Georgia had learned that we’d hide food, but she’d have no clue about the location. She had learned to carefully watch Reinette, who would walk around as nonchalantly as possible while gradually bringing Georgia closer and closer to the concealed cucumber. With Reinette sitting nearby, Georgia would eagerly dig up the veggie. While she was busy, Reinette would hurry toward the banana.

The more experiments we conducted, though, the more Georgia caught on to these deceptive tactics. It is an unwritten rule among chimps that once something is in your hands or mouth, it is yours, even if you are of low status. Before this moment, however, when two individuals approach food, the dominant will enjoy priority. For Georgia, therefore, the trick was to arrive at the banana before Reinette could put her hands on it. After many tests with different combinations of individuals, Katie concluded that high-status chimps exploit the other’s knowledge by carefully monitoring their gaze direction, looking where they are looking. Their partners, on the other hand, do their utmost to conceal their knowledge by not looking where they don’t want the other to go. Both chimps seem exquisitely aware that one possesses knowledge that the other lacks.14

This cat-and-mouse setup shows how much bodies matter. Much of our knowledge about ourselves comes from inside our bodies, and much of what we know about others comes from reading their body language. We are very attuned to the postures, gestures, and facial expressions of others, as are many other animals, such as our pets. This is why Menzel never liked the “theory” language that took over once ToM exploded as a topic as a result of other ape research. The central question became whether apes or children hold a theory about the minds of others.15 I have trouble with this terminology, too, because it makes it sound as if we understand others through a rational evaluation not unlike the way we figure out physical processes, such as how water freezes or how continents drift apart. It sounds far too cerebral and disembodied. I seriously doubt that we, or any other animal, grasp the mental states of someone else at such an abstract level.

Some even speak of mindreading, a term reminiscent of the telepathic trickery of magicians (“Let me guess what card you have in mind”). The magician, however, operates entirely on the basis of which card he has seen you lay your eyes on, or some other visual cue, because there is no such thing as mindreading. All we can do is figure out what others have seen, heard, or smelled, and deduce from their behavior what their next step may be. Putting all this information together is no minor feat and takes extensive experience, but it is body reading, not mindreading. It allows us to look at a situation from the viewpoint of another, which is why I prefer the term perspective taking. We use this capacity to our own advantage but also to the advantage of others, such as when we respond to someone else’s distress or fulfill the needs of another person. This obviously gets us closer to empathy than ToM.

Human empathy is a critically important capacity, one that holds entire societies together and connects us with those whom we love and care about. It is far more fundamental to survival, I’d say, than knowing what others know. But since it belongs to the large submerged part of the iceberg—traits that we share with all mammals—it doesn’t garner the same respect. Moreover, empathy sounds emotional, something cognitive science tends to look down upon. Never mind that knowing what others want or need, or how best to please or assist them, is likely the original perspective taking, the kind from which all other kinds derive. It is essential for reproduction, since mammalian mothers need to be sensitive to the emotional states of their offspring, when they are cold, hungry, or in danger. Empathy is a biological imperative.16

Empathic perspective taking, defined by the father of economics, Adam Smith, as “changing places in fancy with the sufferer,” is well known outside of our species, including dramatic cases of apes, elephants, or dolphins helping one another under dire circumstances.17 Consider how an alpha male chimpanzee at a Swedish zoo saved the life of a juvenile. The juvenile had entangled himself in a rope and was choking to death. The male lifted him up (thus removing the rope’s pressure) and carefully unwrapped the rope from his neck. He thus demonstrated an understanding of the suffocating effect of ropes and knew what to do about it. Had he pulled at the juvenile or the rope, he only would have made things worse.

Two dolphins support a third by taking her between them. They buoy the stunned victim so that her blowhole is above the surface, whereas their own blowholes are submerged. After Siebenaler and Caldwell (1956).

I speak of targeted helping, which is assistance based on an appreciation of the other’s precise circumstances. One of the oldest reports in the scientific literature concerns an incident, in 1954, off the coast of Florida. During a capture expedition for a public aquarium, a stick of dynamite was set off under the water surface near a pod of bottlenose dolphins. As soon as one stunned victim surfaced, heavily listing, two other dolphins came to its aid: “One came up from below on each side, and placing the upper lateral part of their heads approximately beneath the pectoral fins of the injured one, they buoyed it to the surface in an apparent effort to allow it to breathe while it remained partially stunned.” The two helpers were submerged, which meant that they couldn’t breathe during the entire effort. The pod remained nearby and waited until their companion recovered, after which they all fled in a hurry, taking tremendous leaps.18

Another case of targeted helping occurred one day at Burgers’ Zoo. After having cleaned the indoor hall and before releasing the chimps, the keepers hosed out all the rubber tires and hung them one by one on a horizontal log extending from the climbing frame. Upon seeing the tires, female Krom wanted one in which some water remained. The chimps often use tires as vessels to drink from. Unfortunately, this particular tire was at the end of the row, with multiple heavy tires hanging in front of it. Krom pulled and pulled at the one she wanted but was unable to move it. She worked in vain on this problem for over ten minutes, ignored by everyone except Jakie, a seven-year-old that she had taken care of as a juvenile. As soon as Krom gave up and walked away, Jakie approached the scene. Without hesitation he pushed the tires off the log one by one, beginning with the front one, followed by the second in the row, and so on, as any sensible chimp would. When he reached the last tire, he carefully removed it so that no water was spilled and carried it straight to his aunt, placing it upright in front of her. Krom accepted his present without any special acknowledgment and was already scooping up water with her hand when Jakie left.19

Having gone over numerous incidents of insightful assistance in The Age of Empathy, I am pleased that there are now finally controlled experiments.20 For example, at the PRI where Ayumu lives, two chimps were placed side by side while one had to guess what kind of tool the other needed to reach attractive food. The first chimp had a choice between a range of tools—such as a straw to suck up juice or a rake to move food closer—only one of which would work for her partner. She’d need to look at and judge her partner’s situation before handing her the most useful tool through a window. This is indeed what the chimps did, showing a capacity to grasp the specific needs of others.21

The next question is, do primates recognize one another’s internal states, such as the difference between a partner who is hungry and one who is sated? Would you give up precious food for someone who has just eaten a big meal right in front of you? This is the question Japanese primatologist Yuko Hattori asked the monkeys in our capuchin colony.

Capuchins can be quite generous and are great social eaters, often sitting in clusters munching together. When a pregnant female hesitates to descend to the floor to collect her own fruits (being arboreal, these monkeys feel safer higher up), we have seen other monkeys grab more than they need and bring handfuls of food up to her. In the experiment, we separated two monkeys with mesh wide enough to stick their arms through, while one of them received a small bucket with apple slices. Under these circumstances, the provisioned monkey often brings food to its empty-handed partner. They sit next to the mesh partition and let the other one reach through to take food out of their hands or mouth, sometimes actively pushing it in their direction. This is remarkable, because the circumstances allow the possessor to avoid sharing altogether by staying away from the mesh. We found one exception to their generosity, however: if their partner had just eaten, the monkeys became stingy. Of course, this could be due to a sated partner being less interested in food, but the monkeys were stingy only if they had actually seen their partner eat. A partner that had been fed out of sight was treated as generously as any other. Yuko concluded that the monkeys judged the need, or lack thereof, of their companions based on what they had seen them eat.22

In children, an understanding of needs and desires develops years before they realize what others know. They read “hearts” well before they read minds. This suggests that we are on the wrong track in phrasing all this in terms of abstract thinking and theories about others. At a young age, children recognize, for example, that a child looking for his rabbit will be happy to find it, whereas a child searching for his dog will be indifferent to the rabbit.23 They have an understanding of what others want. Not all humans take advantage of this capacity, which is why we have two kinds of gift-givers: those who go out of their way to find a gift that you might like, and those who arrive with what they like. Even birds do better than that. In one of those cognitive ripples typical of our field, empathic perspective taking has been suggested for corvids. Male Eurasian jays court their mates by feeding them delicious tidbits. On the assumption that every male likes to impress, experimenters gave him two foods to choose from: wax moth larvae and mealworms. But before giving the male a chance to feed his mate, they would feed her first with one of those two foods. Seeing this, the male would change his choice. If his mate had just eaten a lot of wax moth larvae, he’d pick mealworms for her instead, and vice versa. He did so, however, only if he had witnessed her being fed by the experimenter. Male birds thus took into account what their mate had just eaten, perhaps assuming that she’d be ready for a change of taste.24 Jays, too, may attribute preferences to others, taking another’s point of view.

At this point, you may wonder why perspective taking was ever declared uniquely human. For this, we need to look at a series of ingenious experiments in the 1990s in which chimpanzees could gain information about concealed food either from an experimenter who had witnessed the hiding process or from another one who had been put in the corner with a bucket over his head. Obviously, they should ignore the second experimenter, who had no idea, and follow the directions of the first. They made no distinction, however. Or an ape could beg for cookies from an experimenter sitting out of reach with a blindfold over his eyes. Would the chimps understand that there was no point stretching out an open hand to someone who cannot see them? After a great variety of such tests, the conclusion was that chimpanzees fail to understand the knowledge that others have and don’t even realize that knowing requires seeing. It was a most peculiar conclusion, given that the main researcher himself relates how playful apes put buckets or blankets over their heads and walk around until they bump into each other. When he himself put things over his head, however, he immediately became the target of play attacks by these apes, who exploited his obscured vision.25 They knew he couldn’t see them and tried to catch him by surprise.

I knew a couple of juvenile male chimps who loved to throw rocks at us, practicing their impressive long-range aim, invariably doing so as soon as I moved my camera to my eye, which made me lose visual contact. Such behavior alone tells us that apes know something about the vision of others and that tests with blindfolds must therefore be missing something. But as happens so often among experimentalists, behavior in the testing room was given priority over real-life observations. As a result, human exceptionalism was loudly proclaimed, most dramatically by concluding that apes do not possess “anything remotely resembling a ToM.”26

This conclusion was warmly greeted and is still being broadcast today even though it has not held up to scrutiny. At my home institution, the Yerkes Primate Center, David Leavens and Bill Hopkins conducted tests in which they placed a banana outside a chimpanzee enclosure where humans regularly walked by. Would the chimps draw attention to get people to hand them the fruit? Would they distinguish between people who could see them and those who could not? If so, this would suggest that they grasped another individual’s visual perspective. The chimps did, because they’d give visual signals to people who looked in their direction, but they’d vocalize and bang on metal if people failed to notice them. They even pointed at the banana to clarify their wishes. One chimpanzee, afraid to be misunderstood, pointed first with her hand at the banana and then with a finger at her own mouth.27

Intentional signaling is not limited to captive apes, as became clear when scientists put a fake snake on the path of wild chimpanzees. Recording the apes’ alarm calls in a Ugandan forest, they found that calling is not just a reflection of fear, because the chimps vocalize regardless of whether the snake is near or far. It is rather a warning intended for others: they call more when others are present, especially friends who have failed to notice the serpent. Callers look back and forth between nearby chimps and the danger, calling more to companions who are naïve about it than to those who already know. Callers thus specifically inform those who lack knowledge, likely because they realize how knowing requires seeing.28

A critical test of this connection was conducted by Brian Hare, then a student here at the Yerkes Primate Center. Brian wanted to know if apes exploit information about another’s visual input. A low-ranking individual was enticed to pick up food in front of a high-ranking one. This is a tricky thing to do, and most subordinates shy away from the confrontation. They were offered a choice between pieces of food that the dominant individual had seen being hidden and pieces hidden without him knowing. The subordinate, on the other hand, had watched it all. In an open competition, like an Easter egg hunt, the safest bet for the subordinate would be to pick only those food items that the dominant had no clue about. This is exactly what they did, showing that they understood that if the dominant had not seen the hiding process, he couldn’t know.29 Brian’s study threw the question of animal ToM wide open again. In an unexpected twist, one capuchin monkey at the University of Kyoto and several macaques at a Dutch research center recently passed similar tasks.30 This is why the whole notion that visual perspective taking is limited to our species is now in the trash bin. Each of the above experiments in and of itself may not be entirely watertight, but taken together they come down on the side of perspective-taking abilities in other species.

It is a testimony to Menzel’s pioneering work that we keep hiding food or snakes, and pitting guessers against knowers. It remains the classical paradigm to assess these capacities both in humans and in other species. Perhaps most telling is an experiment by Menzel’s son Charles. Like his father, Charlie Menzel is a deep thinker, unsatisfied with easy tests or simple answers. At the Language Research Center here in Atlanta, he’d let a female chimp named Panzee watch while he hid food in the pine forest around her outdoor enclosure. Charlie would dig a small hole in the ground to put a bag of M&Ms into it, or place a candy bar in the bushes. Panzee would follow the process from behind bars. Since she could not go where Charlie was, she would need human help to eventually get the hidden food. Sometimes Charlie would hide it after all other people had gone for the day. This meant Panzee could not communicate with anybody about what she knew until the next morning. When the caretakers arrived, they were unaware of the experiment. Panzee first had to get their attention, then provide information to someone who had no clue as to what she was “talking” about.

During a live demonstration of Panzee’s skills, Charlie told me that caretakers generally have a higher opinion of apes’ mental abilities than does the typical philosopher or psychologist. This high opinion was essential for his experiment, he explained, because it meant that Panzee was dealing with people who took her seriously. All those recruited by Panzee said they were at first surprised by her behavior but soon understood what she wanted them to do. By following her pointing, beckoning, panting, and calling, they had no trouble finding the candies hidden in the forest. Without her instructions, they would never have known where to look. Panzee never pointed in the wrong direction, or to locations that had been used on previous occasions. The result was communication about a past event, present in the ape’s memory, to ignorant members of a different species. If the human followed the instructions correctly and got closer to the food, Panzee would vigorously bob her head in affirmation (like “Yes! Yes!”), and like us, she’d lift her hand up, giving higher points, if the item was farther away. She realized that she knew something that the other didn’t know, and was intelligent enough to recruit humans as willing slaves to obtain the goodies of her desire.31

Just to illustrate how creative chimps can be in this regard, here is a typical incident at our field station. A young female grunted at me from behind a fence and kept looking at me with shiny eyes (indicating that she knew something exciting) alternated with pointed stares into the grass near my feet. I couldn’t figure out what she wanted, until she spat. From the trajectory, I noticed a small green grape. When I gave it to her, she ran to another spot and repeated her performance. Having memorized the locations of fruits dropped by the caretakers, she proved an accurate spitter, collecting three rewards this way.

Clever Hans in Reverse

So why did we at first reach the wrong conclusion about animal perspective taking, and why has it happened so many times before and since? Claims about absent capacities range from the idea that primates do not care about the welfare of others, do not imitate, or even fail to understand gravity. Imagine this for flightless animals that travel high above the ground! In my own career, I have faced resistance to the notion that primates reconcile after fights or console those who are distressed. Or at least I heard the counterclaim that they do not truly do so—as in, they do not “truly imitate” or “truly console”—which immediately gets one into debates about how to distinguish what looks like consolation or imitation from the real thing. At times, the overwhelming negativity got to me, as an entire literature burgeoned that was more excited about the cognitive deficits of other species than about their actual accomplishments.32 It would be like having a career adviser who all the time tells you that you are too dumb for this or too dumb for that. What a depressing attitude!

The fundamental problem with all these denials is that it is impossible to prove a negative. This is no minor issue. When anyone claims the absence of a given capacity in other species, and speculates that it must therefore have arisen recently in our lineage, we hardly need to inspect the data to appreciate the shakiness of such a claim. All we can ever conclude with some certainty is that we have failed to find a given skill in the species that we have examined. We cannot go much further than this, and we certainly may not turn it into an affirmation of absence. Scientists do so all the time, though, whenever the human-animal comparison is at stake. The zeal to find out what sets us apart overrides all reasonable caution.

Not even with regard to the Monster of Loch Ness or the Abominable Snowman will you ever hear anyone claim to have proven its nonexistence, even though this would fit the expectations of most of us. And why do governments still spend billions of dollars to search for extraterrestrial civilizations while there is no shred of evidence to encourage this quest? Isn’t it time to conclude once and for all that these civilizations simply don’t exist? But this conclusion will never be reached. That respected psychologists ignore the recommendation to tread lightly around absent evidence is most puzzling, therefore. One reason is that they test apes and children in the same manner—at least in their minds—while coming up with contrary results. Applying a battery of cognitive tasks to both apes and children and finding not a single result in the apes’ favor, they tout the differences as proof of human uniqueness. Otherwise, why didn’t the apes fare better? To understand the flaw in this logic, we need to go back to Clever Hans, the counting horse. But instead of using Hans to illustrate why animal capacities are sometimes overrated, this time we are concerned with the unfair advantage that human capacities enjoy.

The outcome of ape-child comparisons themselves suggests the answer. When tested on physical tasks, such as memory, causality, and the use of tools, apes perform at about the same level as two-and-a-half-year-old children, but when it comes to social skills, such as learning from others or following others’ signals, they are left in the dust.33 Social problem solving requires interaction with an experimenter, however, whereas physical problem solving does not. This raises the possibility that the human interface is key. The typical format of an experiment is to let apes interact with a white-coated barely familiar human. Since experimenters are supposed to be bland and neutral, they do not engage in schmoozing, petting, or other niceties. This doesn’t help make the ape feel at ease and identify with the experimenter. Children, however, are encouraged to do so. Moreover, only the children are interacting with a member of their own species, which helps them even more. Nevertheless, experimenters comparing apes and children insist that all their subjects are treated exactly the same. The inherent bias of this arrangement has become harder to ignore, however, now that we know more about ape attitudes. A recent eye-tracking study (which precisely measured where subjects looked) reached the unsurprising conclusion that apes consider members of their own species special: they follow the gaze of another ape more closely than they follow the human gaze.34 This may be all we need to explain why apes fare poorly on social tasks presented by members of our species.

There are only a dozen institutes that test ape cognition, and I have visited most of them. I have noticed procedures in which humans barely interact with their subjects and ones in which they have close physical contact. The latter can safely be done only by those who raised the apes themselves or have at least known them since infancy. Since apes are much stronger than we are and have been known to kill people, the up-close-and-personal approach is not for everyone. The other extreme derives from the traditional approach in the psychology lab: carrying a rat or a pigeon into a testing room with as little contact as possible. The ideal here is a nonexistent experimenter, meaning the absence of any personal relation. In some labs apes are called into a room and given only a few minutes to perform before they are sent out again without any playful or friendly contact, almost like a military drill. Imagine if children were tested under such circumstances: how would they fare?

At our center in Atlanta, all our chimps are reared by their own kind and so are more ape- than human-oriented. They are “chimpy,” as we say, relative to apes that have a less social background or were raised by humans. We never share the same space with them, but we do interact through the bars, and we always play or groom before testing. We talk to them to put them at ease, give them goodies, and in general try to create a relaxed atmosphere. We want them to look upon our tasks as a game rather than as work, and certainly never put them under pressure. If they are tense because of events in their group, or because another chimp is banging on the outside door or hooting his lungs out, we wait until everyone has calmed down, or we reschedule the test. There is no point testing apes who are not ready. If such procedures are not followed, apes may act as if they don’t understand the problem at hand, whereas the real issue is high anxiety and distraction. Many negative results in the literature may be explained this way.

The methodology sections of scientific papers rarely offer a look in the “kitchen,” but I think it is crucial. My own approach has always been to be firm and friendly. Firm, meaning that we are consistent and don’t make capricious demands but also don’t let the animals walk all over us, such as when they only want to play around and get free sweets. But we are also friendly, without punishment, anger, or attempts to dominate. The latter still happens all too often in experiments and is counterproductive with such headstrong animals. Why would an ape follow the points and prompts of a human experimenter whom he sees as a rival? This is another potential source of negative outcomes.

My own team typically cajoles, bribes, and sweet-talks its primate partners. Sometimes I feel like a motivational speaker, such as when Peony, one of our oldest females, ignored a task that we had set up for her. For twenty minutes, she lay in the corner. I sat down right next to her and told her, in a calm voice, that I didn’t have all day and it would be great if she would get going. She slowly got up, glancing at me, and strolled to the next room, where she sat down for the task. Of course—as discussed in the previous chapter in relation to Robert Yerkes—it is unlikely that Peony followed the details of what I had said. She was sensitive to my tone of voice and knew all along what we wanted.

However good our relations with apes, the idea that we can test them in exactly the same way we test children is an illusion of the same order as someone throwing both fish and cats into a swimming pool and believing he is treating them the same way. Think of the children as the fish. While testing them, psychologists smile and talk all the time, giving instructions where to look or what to do. “Look at the little froggy!” tells a child so much more than an ape will ever know about the green plastic blob in your hand. Moreover, children are usually tested with a parent in the room, often sitting on their lap. Having permission to run around and an experimenter of their own species, they have an enormous leg up over the ape sitting behind bars without verbal hints or parental support.

True, developmental psychologists try to reduce the influence of parents by telling them not to talk or point, and they may give them sunglasses or a baseball cap to cover their eyes. These measures, however, reveal their woeful underestimation of the power of a parent’s motivation to see their child succeed. When it comes to their precious offspring, few people care about the objective truth. We can be glad that Oskar Pfungst designed far more rigorous controls while examining Clever Hans. In fact, Pfungst found that the wide-rimmed hat of the horse owner greatly benefited Hans, since hats amplify head movements. In the same way that the owner vociferously denied his effect on the horse even after it had been proven, parents of children may be completely honest about suppressing cues. But adults have far too many ways to unintentionally guide the choices of a child on their lap, through slight body movements, gaze direction, halted breathing, sighs, squeezes, strokes, and whispered encouragements. Letting parents attend the testing of a child is asking for trouble—the sort of trouble we avoid in animal testing.

The American primatologist Allan Gardner—who was first to teach American Sign Language to an ape—discussed human biases under the heading “Pygmalion leading.” Pygmalion, in ancient mythology, was a Cypriot sculptor who fell in love with his own statue of a woman. The story has been used as a metaphor of how teachers raise the performance of certain children by expecting the world of them. They fall in love with their own prediction, which serves as a self-fulfilling prophecy. Remember how Charlie Menzel felt that only people who hold apes in high esteem will fully appreciate what they are trying to communicate? His was a plea for raised expectations, which unfortunately is not the situation apes typically face. Children, in contrast, are treated in such a nurturing manner that they inevitably confirm the mental superiority ascribed to them.35 Experimenters admire and stimulate them from the outset, making them feel like fish in the water, whereas they often treat apes more like albino rats: keeping them at a distance, and in the dark, while depriving them of the verbal encouragement we offer members of our own species.

The cognition of children and apes is tested in superficially similar ways. Yet children are not kept behind a barrier; they are talked to and often sit on their parents’ laps, all of which helps them connect with the experimenter and receive unintentional hints. The greatest difference, however, is that only apes face a member of another species. Given how much these comparisons disadvantage one class of subjects, they remain inconclusive.

Needless to say, I view most ape-child comparisons as fatally flawed.36

Recall that apes have been tested for ToM by having them guess what humans know or don’t know. The problem here is that captive apes have every reason to believe that we are omniscient! Suppose my assistant calls to tell me that Socko, the alpha male, has been wounded in a fight. I head over to the field station, walk up to him, and ask him to turn around, which he does—having known me since he was a baby—to show me his behind with the gash. Now try to look at this from Socko’s perspective. Chimps are smart animals, always trying to figure out what’s going on. Of course, he wonders how I know about his injury—I must be an all-knowing god. As such, human experimenters are about the last to be used to find out if apes understand the connection between seeing and knowing. All we are testing is the ape’s theory of the human mind. It is no accident that we made substantial progress only after egg-hunt scenarios pitted apes against other apes.

One area of cognitive research that has been lucky to escape the species barrier is the study of ToM in animals that are so different from us that everyone understands that humans are unsuitable partners. This has been the case with corvids. Since a true animal watcher never takes a break, the British ethologist Nicky Clayton made a major discovery over lunch at the University of California at Davis. While sitting at an outdoor terrace, she saw Western scrub jays fly off with scraps stolen from the tables. They not only cached them but also guarded them against thieves. If another bird saw where they hid their food, it was bound to disappear. Clayton noticed that after their rivals left the scene, many of the jays returned to rebury their treasures. In follow-up research with Nathan Emery in their lab at Cambridge, she let jays cache mealworms either in private or while being watched by another jay. Given a chance, the jays quickly re-cached their worms at a new location—but only if they had been watched. They seemed to understand that the food was safe if no other birds had any information. Moreover, only birds who themselves had pilfered others’ food re-cached their own. Following the dictum “It takes a thief to know a thief,” the jays seemed to extrapolate from their own criminality to that of others.37

A Western scrub jay caches a mealworm while being watched from behind glass by another. As soon as he is alone, the jay will quickly rehide his treasures, as if realizing that the other knows too much.

Again, we recognize the Menzel-like design of this experiment, which is even more obvious in a study of perspective-taking ravens. The Austrian zoologist Thomas Bugnyar had a low-ranking male who was expert at opening canisters that contained goodies, but this male often lost his prize to a bullying and stealing dominant male. The low-ranking male, however, learned to distract his competitor by enthusiastically opening empty containers and making as if to eat from them. When the dominant bird found out, “he got very angry, and started throwing things around.” Bugnyar further found that when ravens approach hidden food, they take into account what other ravens know. If their competitors have the same knowledge, they hurry to get there first. But if the others are ignorant, they take their time.38

All in all, animals do plenty of perspective taking, from being aware of what others want to knowing what others know. A few frontiers are left, of course, such as whether they recognize when others have the wrong knowledge. In humans, researchers test this issue with the so-called false-belief task. But since these refinements are hard to evaluate without language, we face a dearth of animal data. Still, even if the remaining differences hold up, there is little doubt that the blanket assertion that ToM is uniquely human must be downgraded to a more nuanced, gradualist view.39 Humans probably possess a fuller understanding of one another, but the contrast with other animals is not stark enough that extraterrestrials would automatically pick ToM as the chief marker that sets us apart.

While this conclusion is based on solid data from repeated experiments, let me add one anecdote that captures the phenomenon in an entirely different way. At the Yerkes Field Station—where apes live in grassy open-air enclosures in the warm Georgia weather—I developed a special bond with an exceptionally bright female chimp named Lolita. One day Lolita had a new baby, and I wanted to get a good look at it. This is hard to do since a newborn ape is really no more than a little dark blob against its mother’s dark tummy. I called Lolita out of her grooming huddle, high up in the climbing frame, and pointed at her belly as soon as she sat down in front of me. Looking at me, she took the infant’s right hand in her right hand and its left hand in her left hand. It sounds simple, but given that the baby was ventrally clinging to her, she had to cross her arms to do so. The movement resembled that of people crossing their arms when grabbing a T-shirt by its hems in order to take it off. She then slowly lifted the baby into the air while turning it around its axis, unfolding it in front of me. Suspended from its mother’s hands, the baby now faced me instead of her. After it made a few grimaces and whimpers—infants hate to lose touch with a warm belly—Lolita quickly tucked it back into her lap.

With this elegant motion, Lolita demonstrated that she realized I would find the front of her newborn more interesting than its back. To take someone else’s perspective represents a huge leap in social evolution.

Spreading Habits

Decades ago friends of mine were outraged by a newspaper article that ranked the smartest canine breeds. They happened to own the breed that was dead last on the list: the Afghan hound. Naturally, the top breed was the border collie. My insulted friends argued that the only reason Afghans were considered dim-witted is that they are independent-minded, stubborn, and unwilling to follow orders. The newspaper’s list was about obedience, they said, not intelligence. Afghans are perhaps more like cats, which are not beholden to anyone. This is no doubt why some people rate cats as less intelligent than dogs. We know, however, that a cat’s lack of response to humans is not due to ignorance. A recent study showed that felines have no trouble recognizing their owner’s voice. The deeper problem is that they don’t care, prompting the study’s authors to add: “the behavioral aspects of cats that cause their owners to become attached to them are still undetermined.”40

I had to think of this story when dog cognition emerged as a hot topic. Dogs were depicted as smarter than wolves, perhaps even apes, because they paid better attention to human pointing gestures. A human would point at one out of two buckets, and the dog would check that particular bucket out for a reward. Scientists concluded that domestication had given dogs extra intelligence compared to their ancestors. But what does it mean that wolves fail to follow human pointing? With a brain about one-third larger than a dog’s, I bet a wolf could outsmart its domesticated counterpart anytime—yet all we go by is how they react to us. And who says that the difference in reaction is inborn, a consequence of domestication, and not based on familiarity with the species doing the pointing? It is the old nature-nurture dilemma. The only way to determine how much of a trait is produced by genes and how much by the environment is to hold one of these two constant to see what difference the other one makes. It is a complex problem that is never fully resolved. In the dog-wolf comparison, this would mean raising wolves like dogs in a human household. If they still differ, genetics might be at play.

Raising wolf puppies in the home is a hellish job, though, since they are exceptionally energetic and less rule-bound than dog puppies, chewing up everything in sight. When dedicated scientists raised wolves this way, the nurture hypothesis came out the winner. Human-raised wolves followed hand points as well as dogs. A few differences persisted, though, such as that wolves looked less at human faces than dogs and were more self-reliant. When dogs tackle a problem they cannot solve, they look back at their human companion to get encouragement or assistance—something that wolves never do. Wolves keep trying and trying on their own. Domestication may be responsible for this particular difference. Instead of intelligence, though, it seems more a question of temperament and relations with us—those weird bipedal apes that the wolf evolved to fear and the dog was bred to please.41 Dogs, for example, engage in lots of eye contact with us. They have hijacked the human parental pathways in the brain, making us care about them in almost the same way that we care about our children. Dog owners who stare into their pet’s eyes experience a rapid increase in oxytocin—a neuropeptide involved in attachment and bonding. Exchanging gazes full of empathy and trust, we enjoy a special relationship with the dog.42

Cognition requires attention and motivation, yet it cannot be reduced to either. As we have seen, the same problem troubles the comparison between apes and children, an issue that popped up again in the controversy around animal culture. Whereas in the nineteenth century, anthropologists were still open to the possibility of culture outside our own species, in the twentieth they began to write culture with a capital C while claiming that the trait is what makes us human. Sigmund Freud considered culture and civilization a victory over nature, while the American anthropologist Leslie White, in a book ironically entitled The Evolution of Culture, declared: “Man and culture originated simultaneously—this by definition.”43 Naturally, when the first reports of animal culture came along, defined as habits learned from others—from potato-washing macaques and nut-cracking chimpanzees to bubble-net-hunting humpback whales—they faced a wall of hostility. One line of defense against this offensive notion was to focus on the learning mechanism. If it could be shown that human culture relies on distinct mechanisms, so the thinking went, we might be able to claim culture for ourselves. Imitation became the holy grail of this battle.

To this end, the age-old definition of imitating as “doing an act from seeing it done” had to be changed to something narrower, something more advanced. The category true imitation was born, which requires one individual to intentionally copy another’s specific technique to achieve a specific goal.44 Merely duplicating behavior, such as one songbird learning another’s song, was not enough anymore: it had to be done with insight and comprehension. While imitation is common in lots of animals according to the old definition, true imitation is rare. We learned this fact from experiments in which apes and children were prompted to imitate an experimenter. They’d watch a human model open a puzzle box or rake in food with a tool. While the children copied the demonstrated action, the apes failed, hence the conclusion that other species lack imitative capacities and cannot possibly have culture. The comfort this finding brought to some circles greatly puzzled me, because it did not answer any fundamental questions either about animal culture or about human culture. All it did was draw a flimsy line in the sand.

One can see here the interplay between the redefinition of a phenomenon and the quest to know what sets us apart, but also a deeper methodological problem, because whether apes imitate us or not is wholly beside the point. For culture to arise in a species, all that matters is that its members pick up habits from one another. There are only two ways to make a fair comparison in this regard (if we disregard the third option of having white-coated apes administer tests to both apes and children). One is to follow the wolf example: raise apes in a human home so that they are as comfortable as children around a human experimenter. The second is the so-called conspecific approach, which is to test a species with models of its own kind.

The first solution yielded results right away, because several human-raised apes turned out to be as good at imitating members of our species as were young children.45 In other words, apes, like children, are born imitators and prefer to copy the species that raised them. Under most circumstances, this will be their own kind, but if reared by another species, they are prepared to imitate that one as well. Using us as models, these apes spontaneously learn to brush their teeth, ride bicycles, light fires, drive golf carts, eat with a knife and fork, peel potatoes, and mop the floor. It reminds me of suggestive stories on the Internet about dogs raised by cats, which show feline behavior such as sitting in boxes, crawling under tight spaces, licking their paws to clean their face, or sitting with their front legs tucked in.

Another critical study was conducted by Victoria Horner, a Scottish primatologist, who later became my team’s lead expert on cultural learning. Together with Andrew Whiten of St. Andrews University, Vicky worked with a dozen orphan chimps at Ngamba Island, a sanctuary in Uganda. She acted like a mix between a mother and caretaker for the juvenile apes. Sitting next to her during tests, the juvenile apes were attached to Vicky and eager to follow her example. Her experiment created waves because as in Ayumu’s case, the apes proved to be smarter than the children. Vicky would poke a stick into holes in a large plastic box, going through a series of holes until a candy would roll out. Only one hole mattered. If the box was made of black plastic, it was impossible to tell that some of the holes were just for show. A transparent box, on the other hand, made it obvious where the candies came from. Handed the stick and the box, young chimps mimicked only the necessary moves, at least with the transparent box. The children, on the other hand, mimicked everything that Vicky had demonstrated, including useless moves. They did so even with the transparent box, approaching the problem more like a magic ritual than as a goal-directed task.46

With this outcome, the whole strategy of redefining imitation backfired! After all, it was the apes who best fit the new definition of true imitation. The apes were showing selective imitation, the sort that pays close attention to goals and methods. If imitation requires understanding, we have to give it to the apes, not to the children, who for lack of a better term, showed only dumb copying.

What to do now? Premack complained that it was way too easy to make children look “foolish”—as if that were the goal of the experiment!—whereas in reality, he felt, there must be something wrong with the interpretation.47 His distress was genuine, showing to what degree the human ego gets in the way of dispassionate science. Promptly, psychologists settled on a narrative in which overimitation—a new term for children’s indiscriminate copying—is actually a brilliant achievement. It fits our species’ purported reliance on culture, because it makes us imitate behavior regardless of what it is good for; we transmit habits in full, without every individual making his or her own ill-informed decisions. Given the superior knowledge of adults, the best strategy for a child is to copy them without question. Blind faith is the only truly rational strategy, it was concluded with some relief.

Even more striking were Vicky’s studies at our field station in Atlanta, where we started a decade-long research program in collaboration with Whiten, focusing entirely on the conspecific approach. When chimps were given a chance to watch one another, incredible talents for imitation manifested themselves. Apes truly do ape, allowing behavior to be faithfully transmitted within the group.48 A video of Katie imitating her mother, Georgia, offers a nice example. Georgia had learned to flip open a little door in a box, then stick a rod deep into the opening to retrieve a reward. Katie had watched her mother do this five times, following her every move and smelling Georgia’s mouth every time she got a reward. After her mother was moved to another room, Katie could finally access the box herself. Even before we had added any rewards, she flipped open the door with one hand and inserted the rod with the other. Sitting like this, she looked up at us on the other side of the window and impatiently rapped it, while grunting, as if telling us to hurry up. As soon as we pushed the reward into the box, she retrieved it. Before ever being rewarded for these actions, Katie perfectly duplicated the sequence she had watch Georgia perform.

Rewards are often secondary. Imitation without reward is of course common in human culture, such as when we mimic hairstyles, accents, dance steps, and hand gestures, but it is also common in the rest of the primate order. The macaques on the Arashiyama mountaintop in Japan customarily rub pebbles together. The young learn to do it without any reward other than perhaps the noise associated with it. If one case refutes the common notion that imitation requires reward, it is this weird behavior, about which Michael Huffman, an American primatologist who has studied it for decades, notes, “It is likely that the infant is first exposed in utero to the click-clacking sounds of stones as its mother plays, and then exposed visually as one of the first activities it sees after birth, when its eyes begin to focus on objects around it.”49

The word fashion was first used in relation to animals by K?hler, whose apes invented new games all the time. They’d march single file around and around a post, trotting in the same rhythm with emphasis on one stamping foot, while the other foot stepped lightly, wagging their heads in the same rhythm, all acting in synchrony as if in a trance. For months our own chimps had a game we called cooking. They’d dig a hole in the dirt, collect water by holding a bucket under a faucet, and dump water into the hole. They’d sit around the hole poking in the mud with a stick as if stirring soup. Sometimes there were three or four such holes in operation at the same time, keeping half the group busy. At a chimpanzee sanctuary in Zambia, scientists followed the spread of yet another meme. One female was the first to stick a straw of grass into her ear, letting it hang out while walking around and grooming others. Over the years, other chimps followed her example, with several of them adopting the same new “look.”50

Fashions come and go in chimps as in humans, but some habits we find in only one group and not in another. Typical is the hand-clasp grooming of some wild chimpanzee communities, in which two individuals hold hands above their heads while grooming each other’s armpits with their other hands.51 Since habits and fashions often spread without any associated rewards, social learning is truly social. It is about conformity instead of payoffs. Thus an infant male chimp may mimic the charging display of the alpha male who always bangs a specific metal door to accentuate his performance. Ten minutes after the male has finished his performance—a dangerous activity, during which mothers keep their children near—the little son is let go. With all his hair on end, he goes to bang on the same door as his role model.

Having documented numerous such examples, I developed the idea of Bonding- and Identification-based Observational Learning (BIOL). Accordingly, primate social learning stems from an urge to belong. BIOL refers to conformism born from the desire to act like others and to fit in.52 It explains why apes imitate their own kind far better than the average human, and why, among humans, they imitate only those whom they feel close to. It also explains why young chimps, especially females,53 learn so much from their mothers, and why high-status individuals are favorite models. This preference is also known in our own societies, in which advertisements feature celebrities showing off watches, perfumes, and cars. We love to emulate the Beckhams, Kardashians, Biebers, and Jolies. Might the same apply to apes? In one experiment, Vicky spread brightly colored plastic chips around in an enclosure, which the chimps could collect and carry to a container in exchange for rewards. Exposed to the sight of a top-ranking group member trained to drop tokens into one container and a bottom-ranking one trained to use a different container, the colony massively followed in the footsteps of the more prestigious member.54

As evidence mounted regarding imitation in apes, other species inevitably joined the ranks, showing similar capacities.55 There are now compelling studies on imitation in monkeys, dogs, corvids, parrots, and dolphins. And if we take a broader view, we have even more species to consider because cultural transmission is widespread. To return to dogs and wolves, a recent experiment applied the conspecific approach to canine imitation. Instead of following human instructions, both dogs and wolves saw a member of their own species manipulate a lever to open the lid of a box with hidden food. Next, they were allowed to try the same box themselves. This time the wolves greatly outsmarted the dogs.56 Wolves may be poor at following human pointing, but when it comes to picking up hints from their own kind, they beat dogs. The investigators ascribe this contrast to attention rather than cognition. They point out that wolves watch one another more closely as they rely on the pack for survival, whereas dogs rely on us.

Clearly, it is time for us to start testing animals in accordance with their biology and move away from human-centric approaches. Instead of making the experimenter the chief model or partner, we better keep him or her in the background. Only by testing apes with apes, wolves with wolves, and children with human adults can we evaluate social cognition in its original evolutionary context. The one exception may be the dog, which we domesticated (or which domesticated itself, as some believe) to bond with us. Humans testing dog cognition may actually be a natural thing to do.

Moratorium

Having escaped the Dark Ages in which animals were mere stimulus-response machines, we are free to contemplate their mental lives. It is a great leap forward, the one that Griffin fought for. But now that animal cognition is an increasingly popular topic, we are still facing the mindset that animal cognition can be only a poor substitute of what we humans have. It can’t be truly deep and amazing. Toward the end of a long career, many a scholar cannot resist shining a light on human talents by listing all the things we are capable of and animals not.57 From the human perspective, these conjectures may make a satisfactory read, but for anyone interested, as I am, in the full spectrum of cognitions on our planet, they come across as a colossal waste of time. What a bizarre animal we are that the only question we can ask in relation to our place in nature is “Mirror, mirror on the wall, who is the smartest of them all?”

Keeping humans in their preferred spot on that absurd scale of the ancient Greeks has led to an obsession with semantics, definitions, and redefinitions, and—let’s face it—the moving of goalposts. Every time we translate low expectations about animals into an experiment, the mirror’s favorite answer sounds. Biased comparisons are one ground for suspicion, but the other is the touting of absent evidence. I have lots of negative findings in my own drawers that have never seen the light since I have no idea what they mean. They may indicate the absence of a given capacity in my animals, but most of the time, especially if spontaneous behavior suggests otherwise, I am unsure that I have tested them in the best possible way. I may have created a situation that threw them off, or presented the problem in such an incomprehensible fashion that they didn’t even bother to solve it. Recall the low opinion scientists held of gibbon intelligence before their hand anatomy was taken into account, or the premature denials of mirror self-recognition in elephants based on their reaction to an undersize mirror. There are so many ways to account for negative outcomes that it is safer to doubt one’s methods before doubting one’s subjects.

Books and articles commonly state that one of the central issues of evolutionary cognition is to find out what sets us apart. Entire conferences have been organized around the human essence, asking “What makes us human?” But is this truly the most fundamental question of our field? I beg to differ. In and of itself, it seems an intellectual dead end. Why would it be any more critical than knowing what sets cockatoos or beluga whales apart? I am reminded of one of Darwin’s random musings: “He who understands baboon would do more towards metaphysics than Locke.”58 Every single species has profound insights to offer, given that its cognition is the product of the same forces that shaped ours. Imagine a medical textbook that declared that its discipline’s central issue is to find out what is unique about the human body. We would roll our eyes, because even though this question is mildly intriguing, medicine faces far more basic issues related to the functioning of hearts, livers, cells, neural synapses, hormones, and genes.

Science seeks to understand not the rat liver or the human liver but the liver, period. All organs and processes are a great deal older than our species, having evolved over millions of years with a few modifications specific to each organism. Evolution always works like this. Why would cognition be any different? Our first task is to find out how cognition in general operates, which elements it requires to function, and how these elements are attuned to a species’s sensory systems and ecology. We want a unitary theory that covers all the various cognitions found in nature. To create space for this project, I recommend placing a moratorium on human uniqueness claims. Given their miserable track record, it is time to rein them in for a few decades. This will allow us to develop a more comprehensive framework. One day years from now, we may then return to our species’s particular case armed with new concepts that allow a better picture of what is special—and what not—about the human mind.

One aspect we might focus on during this moratorium is an alternative to overly cerebral approaches. I have already mentioned that perspective taking is likely tied to bodies, and the same applies to imitation. After all, imitation requires that another individual’s body movements are perceived and translated into one’s own body movements. Mirror neurons (special neurons in the motor cortex that map another’s actions onto one’s own bodily representations in the brain) are often thought to mediate this process, and it is good to realize that those neurons were discovered not in humans but in macaques. Even though the precise connection remains a point of debate, imitation likely is a bodily process facilitated by social closeness.

This view is quite different from the cerebral one according to which it all depends on the understanding of cause-effect relations and goals. Thanks to an ingenious experiment by the British primatologist Lydia Hopper, we know which view is correct. Hopper presented chimps with a so-called ghost box controlled by fishing lines. The box magically opened and closed by itself, producing rewards. If technical insight were all that mattered, watching such a box should suffice, as it shows all the necessary actions and consequences. But in fact, letting chimps watch the ghost box ad nauseam taught them nothing. Only after seeing an actual chimp operate the same box, did they learn how to get the rewards.59 Thus for imitation to occur, apes need to connect to a moving body, preferably one of their own species. Technical understanding is not the key.60

To find out how bodies interact with cognition, we have incredibly rich material to work with. Adding animals to the mix is bound to stimulate the up-and-coming field of “embodied cognition,” which postulates that cognition reflects the body’s interactions with the world. Until now, this field has been rather human-focused while failing to take advantage of the fact that the human body is only one of many.

Consider the elephant. It combines a very different body with the brainpower to achieve high cognition. What is the largest land mammal doing with three times as many neurons as our own species? One may downplay this number, arguing that it has to be corrected for body mass, but such corrections are more suited to brain weight than to number of neurons. In fact, it has been proposed that absolute neuron count, regardless of brain or body size, best predicts a species’ mental powers.61 If so, we’d better pay close attention to a species that has vastly more neurons than we do. Since most of these neurons reside in the elephant’s cerebellum, some feel they carry less weight, the assumption being that only the prefrontal cortex matters. But why take the way our brain is organized as the measure of all things and look down on subcortical areas?62 For one thing, we know that during Hominoid evolution, our cerebellum expanded even more than our neocortex. This suggests that for our species, too, the cerebellum is critically important.63 It is now up to us to find out how the remarkable neuron count of the elephant brain serves its intelligence.

The trunk, or proboscis, is an extraordinarily sensitive smelling, grasping, and feeling organ said to contain forty thousand muscles coordinated by a unique proboscis nerve that runs along its full length. The trunk has two sensitive “fingers” at the tip, with which it can pick up items as small as a blade of grass, but the trunk also allows the animal to suck up eight liters of water or flip over an annoying hippo. True, the cognition associated with this appendage is specialized, but who knows how much of our own cognition is tied to the specifics of our bodies, such as our hands? Would we have evolved the same technical skills and intelligence without these supremely versatile appendages? Some theories of language evolution postulate its origin in manual gestures as well as in neural structures for the throwing of stones and spears.64 In the same way that humans have a “handy” intelligence, which we share with other primates, elephants may have a “trunky” one.

There is also the issue of continued evolution. It is a widespread misconception that humans kept evolving while our closest relatives stopped. The only one who stopped, however, is the missing link: the last common ancestor of humans and apes, so named because it went extinct long ago. This link will forever remain missing unless we happen to dig up some fossil remains. I named my research center Living Links, in a wordplay on the missing link, since we study chimpanzees and bonobos as live links to the past. The name has caught on, because there are now a few other Living Links centers in the world. Traits shared across all three species—our two closest ape relatives and ourselves—likely have the same evolutionary roots.

But apart from commonalities, all three species also evolved in their own separate ways. Since there is no such thing as halted evolution, all three probably changed substantially. Some of these evolutionary changes gave our relatives an advantage, such as the resistance to the HIV-1 virus that evolved in West African chimps long before the AIDS epidemic devastated humanity.65 Human immunity has some serious catching up to do. Similarly, all three species—not just ours—had time to evolve cognitive specializations. No natural law says that our species has to be best at everything, which is why we should be prepared for more discoveries such as Ayumu’s flash memory or the selective imitative talents of apes. A Dutch educational program recently brought out an advertisement in which human children face the floating peanut task (see Chapter 3). Even though the members of our species have a bottle of water standing not too far away, they fail to think of the solution until they see a video of apes solving the same problem. Some apes do so spontaneously, even when there is no bottle around to suggest what to do. They walk to the faucet where they know water can be collected. The point of the ad is that schools should teach kids to think outside the box, using apes as an inspiration.66

The more we know about animal cognition, the more examples of this kind may come to light. The American primatologist Chris Martin, at the PRI in Japan, has added yet another chimpanzee forte. Using separate computer screens, he had apes play a competitive game that required them to anticipate one another’s moves. Could they outguess their rivals based on their previous choices, a bit like the rock-paper-scissors game? Martin had humans play the same game. The chimps outperformed the humans, reaching optimal performance more quickly and completely than members of our own species. The scientists attributed the edge to chimps being quicker at predicting a rival’s moves and countermoves.67

This finding resonated with me, given what I know about the politics and preemptive tactics of chimpanzees. Chimp status is based on alliances, in which males support one another. Reigning alpha males protect their power by a divide-and-rule strategy, and they particularly hate it when one of their rivals cozies up to one of their own supporters. They try to forestall hostile collusions. Moreover, not unlike presidential candidates who hold babies up in the air as soon as the cameras are rolling, male chimps vying for power develop a sudden interest in infants, which they hold and tickle in order to curry favor with the females.68 Female support can make a huge difference in rivalries among males, so making a good impression on them is important. Given the tactical shrewdness of chimpanzees, it is a great advance that computer games now help us put these remarkable skills to the test.

We have no good reason to focus solely on chimpanzees, though. They often serve as a starting point, but “chimpocentrism” is a mere extension of anthropocentrism.69 Why not focus on other species that lend themselves to explore specific aspects of cognition? We could focus on a small number of organisms as test cases. We already do so in medicine and general biology. Geneticists exploit fruit flies and zebra fish, and students of neural development have gotten much mileage out of research on nematode worms. Not everyone realizes that science works this way, which is why scientists were dumbfounded by the complaint of former vice-presidential candidate Sarah Palin that tax dollars were going to useless projects such as “fruit fly research in Paris, France. I kid you not.”70 It may sound silly to some, but the humble Drosophila has long been our main workhorse in genetics, yielding insight in the relation between chromosomes and genes. A small set of animals produces basic knowledge applicable to many other species, including ourselves. The same applies to cognitive research, such as the way rats and pigeons have shaped our view of memory. I imagine a future in which we explore a range of capacities in specific organisms on the assumption of generalizability. We may end up studying technical skills in New Caledonian crows and capuchin monkeys, conformity in guppies, empathy in canids, object categorization in parrots, and so on.

Yet all this requires that we circumvent the fragile human ego and treat cognition like any other biological phenomenon. If cognition’s basic features derive from gradual descent with modification, then notions of leaps, bounds, and sparks are out of order. Instead of a gap, we face a gently sloping beach created by the steady pounding of millions of waves. Even if human intellect is higher up on the beach, it was shaped by the same forces battering the same shore.

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