Are We Smart Enough to Know How Smart Animals Are

by Frans de Waal

  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 the ratio—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, exc
laiming 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.10 But the website 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?11

  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.12

  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.13 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.14

  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.15