What makes us human

Gummy bears. They reveal a sweet reality. Watch the video: A couple of three-year-olds are noisily negotiating a challenge cleverly arranged for them. They pull together on some ropes, thereby unsealing a big-box container and unleashing a flood of the candy treats. It doesn’t take much prodding by either partner to arrive at an equitable distribution; if one points out she’s gummy-deprived, the other will quickly correct the gummy imbalance. There all lots of similar studies, all in support of a grand theory of human uniqueness, and all part of the ever-expanding research record of Michael Tomasello ’71, a Duke professor of psychology and neuroscience.

Tomasello’s drive as a thinker and researcher has earned him a host of honors; their range highlights a career of groundbreaking work in multiple fields. In 2017, he was elected to the National Academy of Sciences, one of the highest awards a scientist can receive. Five years ago, it was the American Psychological Association’s Distinguished Scientific Award. According to the citation, Tomasello’s “pioneering research on the origins of social cognition has led to revolutionary insights in both developmental psychology and primate cognition.” Before that it was the Heineken Prize for Cognitive Science: “He is one of the few scientists worldwide who is acknowledged as an expert in multiple disciplines.”

“More than anyone else,” Tomasello “has helped to specify what makes us unique from and what makes us similar to other animals,” says Andrew Meltzoff, co-director of the Institute for Learning and Brain Sciences at the University of Washington in Seattle. “Many of his experiments are classics in the field, and they have opened our eyes to what it means to be human.”

TOMASELLO’S most eyeopening work to date—which, in sketching out what it means to be human, gathers together some of those classic experiments—is a book published earlier this year. It’s aptly if somewhat grandly titled Becoming Human. His starting point is that we’re separated from our closest primate relatives by small differences. Small differences, but pointing to one very big and very human trait: the impulse to cooperate.

What first put him on the map, in his phrase, was Tomasello’s 1999 book, The Cultural Origins of Human Cognition. There he offers a thought experiment, imagining a child raised on a desert island. The child is removed from all human contact. How would such a child behave? Very much like an ape. “The special part of humans are the capacities we’re born with,” he says. “Those capacities have to be realized through social interactions. They have to be exercised.”

The new book shifts the focus. Culture—a concept that, to Tomasello, embraces creating and using symbols, from math to written language; creating and using complex tools; and, finally, creating and participating in complex social organizations and institutions—plays a big role in making humans human. So what plays a big role in making culture possible?

“As I did more research and thought about it more, I decided that cooperation is more fundamental than culture,” says Tomasello. “You can think of culture as a form of cooperation. You can’t have culture without already having in place an individual psychology that says, ‘I can cooperate with other people.’ Then that psychology of cooperation scales up to the group.” If humans are uniquely capable of forming a culture, that’s because they’re uniquely capable of cooperating.

Tomasello has a broad definition of cooperation. It includes mutualistic collaboration, through which both parties benefit. Along with sacrificing, or altruism, or helping. As he sees it, as we gain experience through our infant years, a somewhat narrow, self-interested, mutualistic collaboration shifts to the more altruistic version of cooperation. Through that process, our moral range expands. “We want to cooperate because it’s mutually beneficial to do so. But we also want to cooperate because we want to distribute the spoils of our joint effort fairly, because we ought to.”

Cooperation, then, eventually deepens the sense of “we,” the notion that we’re all in this together, that we all have a share of some entitlement from our effort.

It’s an idea that grows out of the six hundred or so scientific papers Tomasello has authored or coauthored. A small sampling: “Young Children Mostly Keep, and Expect Others to Keep, Their Promises”; “Toddlers Help a Peer”; “What’s in It for Me? Self-Regard Precludes Altruism and Spite in Chimpanzees”; “Three-Year-Olds’ Reactions to a Partner’s Failure to Perform Her Role in a Joint Commitment”; “Thirty Years of Great Ape Gesturing.”

Since returning to Duke three years ago from the Max Planck Institute for Evolutionary Anthropology, Tomasello has planted his team in the Duke Child Studies labs, a wing of the Social Psychology Building. A whiteboard carries an evocative recruiting message: “You play with colors, we give you a prize. Age range 2.5-4.5 years.” A dozen or so kids’-participation awards line the walls; each includes a photo of one super-young, super-smiling lab subject, and declares that the Tomasello lab “proudly presents the honorable title of junior scientist.” One of the adjacent spaces—nondescript except for kid-distracting features like Dino Fossil Putty, a Secret Decoder, Fish Face swimming goggles, Superman-theme comic books, and plastic characters from Frozen—is being set up for an upcoming experiment. It will look at how one child who’s been awarded a supply of tokens will go about sharing them with another child.

He has a large videotape library of his experiments. Take a look through them and you’ll see in rambunctious action three- and five-year-olds. They’re performing—say, putting a treat in a box for a treat-deprived peer—in environments manufactured to be friendly, with totscaled chairs, huggable stuffed animals, floppy puppets (frogs, bears, rabbits, dogs, cows), and wildly colored posters to dress up the otherwise coldly clinical setting. You’ll also see, with a separate set of experiments, lots of chimpanzees, shown in somewhat less elaborately constructed environments. They’re doing things like pointing to an empty plate and implicitly asking: How about loading this up with some food?

“Of course they’re cute videos,” Tomasello says. “They’re chimps and kids.”

Just over a decade ago, Tomasello was running experiments with infants of fourteen and eighteen months of age, as they were just beginning to walk and talk. He had those infants engage with an adult stranger they had met moments before. They were put in situations where they could help the adult solve some simple problem, from fetching out-of-reach objects to opening cabinet doors when the adult’s hands are full. They were, as it turned out, eager to help. According to Tomasello, that meant they could at once perceive others’ goals in a variety of situations and, then, have the altruistic drive to provide a needed boost.

Would other primates, our close relatives, behave differently? Sure, those other primates might communicate in some rough form. But if they’re really cooperative creatures, they have to be good at figuring out the psychology of their fellow primates.

One of Tomasello’s longtime collaborators, Brian Hare, now a professor of evolutionary anthropology at Duke, recalls that for a long time, scientists were skeptical that other primates could, in any way, “read” the intentions or actions of others. Tomasello himself had been asserting his own skepticism in scientific papers. But Tomasello was happy to test an alternative hypothesis—an indication of the Tomasello trait of being “addicted to discovery,” as Hare describes him. Even if some discovery might prove him wrong.

For his dissertation, under Tomasello’s supervision, Hare ran experiments featuring chimps. Researchers placed food on one side or the other of opaque barriers, so the food was visible or not to a subordinate chimp and a dominant chimp. It turns out that chimps, like humans, are “mind readers”; they were able to figure out who knew what about the food location and would act accordingly.

Hare and Tomasello, along with Josep Call (professor in evolutionary origins of the mind at the University of St. Andrews in Scotland), wrote up the study in the journal Animal Behaviour. They observed that “some subordinates in some trials engaged in strategic maneuvering, such as waiting or hiding to obtain pieces of food, sometimes even using more proactive strategies such as distracting the dominant away from the hidden food.” In other words, chimps aren’t mind reading to share or cooperate. They’re mind reading to compete.

Tomasello elaborated on the human-chimp gap in a 2011 paper in Nature, one of the world’s leading science journals. One experiment had two- or three-year-old children in a room without adults; they were faced with the task of pulling together to bring a board, basically a seesaw, toward them. On each end of the board were two small toys that could be accessed once the board had been pulled close enough. As the children pulled, the toys rolled toward them; one child ended up with three toys, while the other ended up with one. The “lucky” child, who had gained three toys, made one of the toys available to the “unlucky” partner, who had gained one—so that they ended up with the same number.

A parallel experiment focused on chimps. The “lucky” chimp never tipped the reward to the “unlucky” partner; the chimp took the reward for itself. For humans, it was all about restoring equity. For chimps, it was all about grabbing what was available to be grabbed.

“The most basic comparative fact is that, in situations of free choice with rewards for both partners identical, three-year-old children mostly collaborate with a partner, whereas chimpanzees mostly choose to go it alone,” Tomasello writes in a recent paper, “The Moral Psychology of Obligation.” “Children are so motivated to collaborate that they actively attempt to reengage a recalcitrant partner, whereas chimpanzees ignore a recalcitrant partner and, again, attempt to go it alone. Indeed, children are so motivated that they attempt to reengage a recalcitrant partner even when they know they could act alone and reach the same result.”

Humans, he goes on, “have a species-unique motivation and preference, at least among great apes, for pursuing goals by collaborating with others.” Beyond that, children, as they collaborate, relate to one another with an apparent “sense of obligation to treat their partner respectfully, as an equal.”

Meltzoff, the University of Washington researcher in cognition, says Tomasello “has a finely tuned intuition for what are important problems to study.” He adds: “Neither group can speak. Neither understands our language. It is not easy to figure out how to ‘ask’ a chimp a question or how to ‘ask’ a baby what they think or feel. Many have tried. Many have failed.”

THE COOPERATIVE tendency revealed by those human children, in Tomasello’s view, isn’t just incidental in the realm of human experience. It’s a consequence of human evolution. Humans diverged from other great apes around 6 million years ago. They were basically bipedal apes with ape-sized brains for the next 4 million years, when the genus Homo, with larger brains and new skills in making stone tools, emerged. As other primates competed with them for resources, they began obtaining their food through more active collaboration.

Individuals who were uncooperative in their interactions with others—those who tried to hog all the spoils—were avoided as partners. Their evolutionary line came to a stop. The upshot was strong social selection for cooperatively competent and motivated individuals.

Great apes—chimps, gorillas, orangutans, bonobos—evolved to be pretty great at some things. They climb with great agility, they’re on a fast track in their physical development, and from age three or four, they’re essentially independent. If those great apes are biologically adapted for independence, humans are biologically adapted for cooperation.

They’re adapted, that is, to act together as a single agent, with a shared goal, rules of behavior adjusted to coordinate with partners, and implied agreement to share the rewards of their efforts.

Tomasello’s cooperation-minded research questions are, in many ways, the timeless questions of philosophy. About ten years ago, he was awarded Germany’s Hegel Prize, for which he was hailed as a “true philosopher” in the guise of a lab researcher. The new book, Becoming Human, won the William James Book Award of the American Psychological Association for bringing together “diverse subfields of psychology and related disciplines.” An occasional touchstone for him is Scottish Enlightenment philosopher David Hume. Hume sketched out “natural” or humanly innate virtues, such as sympathy, and then “artificial” or socially grounded virtues, such as justice or fairness.

Tomasello closely follows that line: In evolutionary terms, cooperation was a means to procure resources that individuals could never procure on their own. It’s evident, in some form, through early- childhood development. As development proceeds, the child’s cooperative tendencies harden into a group identity.

So an evolutionary imperative translates into a collective imperative—and eventually into human culture. One journal review credits Tomasello’s “impressive and foundational research” for grappling with the last of Immanuel Kant’s great philosophical questions: What is man? Channeling Kant, fellow researcher Josep Call says, “One of the most fundamental questions that humans must grapple with, and not just from a scientific standpoint but also from a philosophical one, is what it means to be human.”

AS A STUDENT at Duke, Tomasello—who for a typical day in the lab, still dresses casually in jeans—faced the usual confusion around what it means to decide on a major. Until he discovered psychology. He happened upon a course with Carl Erickson, now retired, in comparative psychology. “He would talk about how turtles find the beach on which to lay their eggs, how homing pigeons find their home, how honeybees communicate. I just thought it was the most fascinating stuff I had ever heard.”

Tomasello was hooked. He sought out courses in developmental psychology, and then in social psychology and personality.

He was drawn especially to the writings of Jean Piaget, a Swiss psychologist known for his pioneering work on child development. In Duke’s Gothic Bookshop, he picked up a copy of Piaget’s The Origins of Intelligence in Children; the book still has a place in his office. Piaget was interested in how children experience and process the world, and so he became an avid questioner of children: “Where does the moon go at night?” “How do bicycles work?” “How can those big, heavy ships float?” “How do shadows work?”

Inspired by his reading of Piaget, Tomasello, as a Duke junior, took a job at the Watts Street Baptist Church daycare center in Durham. (He had gotten married right after his freshman year; at the time he was commuting between campus and his residence on a farm in Hillsborough.) As he organized play time for the preschoolers there, he applied his own version of Piaget’s questioning. “Piaget’s general idea was that children have a logic of their own. They think in their own way. They are kind of a different species. And you have to figure out how they work.”

Figuring out the route to academic success was a struggle: “This was the 1960s and ’70s, and I was doing things other than studying.” He applied to a bunch of graduate schools, was turned down by every one, and eventually moved to Florida, his home state. For a year he lived by a lake and worked putting together pallets—a cooperative enterprise alongside forklift operators—for one of two pallet- manufacturing companies in the U.S.

He went through another round of grad-school applications; this time, he reeled in one acceptance, from the University of Georgia, and he enrolled there. For his first semester, he had no fellowship support. To earn some money in rural Athens, Georgia, he would wake up at three o’clock in the morning to deliver newspapers. Then he would head to class.

With a Ph.D. in experimental psychology, Tomasello landed a job at Emory University, as an assistant professor of psychology. (Initially he had been turned down, but the preferred candidate withdrew, and he negotiated successfully to be more than a “placeholder” for a future hire.) Soon after arriving, in 1980, he drove out to Emory’s Yerkes Primate Center with a colleague. As he recalls, “We were gushing enthusiastically about how incredibly similar chimpanzees were to humans—in their basic emotions, their playful social interactions, their clever use of tools—when one of them sitting atop a climbing apparatus began urinating. Another sauntered over and opened its mouth to catch the pee. Well, okay, maybe very similar to us, but not identical.”

At that moment, he says, “I could dimly see how exciting it would be to directly compare great apes and human children,” across a spectrum of behavior.

Tomasello advanced through the professorial ranks and at the Yerkes affiliate. In 1998, the Max Planck Institute for Evolutionary Anthropology tapped him as a founding co-director. Based in Leipzig, Germany, and employing a couple of hundred resident and visiting scientists, the institute investigates the history of humankind from multiple perspectives. Those scientists do research in genetics, cognition, and cultures and social systems, along with studies of primates closely related to humans.

Following the fashion of German universities, the institute is very hierarchical; academic responsibilities aren’t broadly distributed. As a result, Tomasello supervised the dissertations of more than fifty Ph.D. students.

He also helped set up (with Josep Call) what became both a major public attraction and a major center for primate research, operated with the Leipzig Zoo. Its research focuses on the behavior and cognition of the great apes: chimps, gorillas, orangutans, bonobos. And its zoo setting allows visitors to observe the apes and observe scientific studies as well.

Among Tomasello’s Leipzig proteges was Duke’s Brian Hare, who had started working with him as a sophomore at Emory. He graduated in three-and-a-half years. Right away he joined Tomasello’s team full time; he kept up that association through his Ph.D.-earning and postdoctoral years. “I thought I was going to play college baseball,” he recalls. “After I met Mike, I gave up baseball and played science instead.”

Hare’s initial work with Tomasello was around the simple but meaningful gaze-following question: If one primate looks up, will another primate, in response, look in the same direction? Hare quickly became invested in designing experiments, collecting data, and sorting through possible interpretations—the hard but imaginative work of science.

One of their early joint papers, published in Science, established what they labeled “the Cultural Intelligence Hypothesis.” The researchers gave a comprehensive battery of cognitive tests to 106 chimpanzees, thirty-two orangutans, and then 105 children age two-and-a-half years. This was a large-scale study; it ran its subjects through a wide range of tasks, like “solving a simple but not obvious problem by observing a demonstrated solution.”

Their overall conclusion: Children and chimps show very similar cognitive skills for dealing with the physical world. But when it comes to dealing with the social world, children have more sophisticated cognitive skills than other primates. It’s not a “general intelligence.” Rather, it’s a special intelligence—a sort of cultural transmission mechanism—through which humans can bond with and learn from others.

The cultural-intelligence study was “the first large-scale cognitive study that compared different species across a wide range of cognitive abilities,” says Hare. Earlier approaches would zero in on a particular ability in a particular subject—then, on to another ability and another subject. Such a drawback led to lots of definitional fuzziness. Researchers might have been studying the same ability but applying different labels.

Now known for heading up the Duke Canine Cognition Center, Hare says his work on dog psychology has built on the Tomasello model: Dogs, not unlike great apes, have a set of cognitive abilities, and their expression varies in individuals. For dogs, they include memory and inhibition. Hare’s own large-scale studies, then, point to one “real world” application of Tomasello’s research methods: They allow him and his colleagues to identify good detection dogs (good memory) or service dogs (strong inhibition).

TINY HUMANS, of course, aren’t very puppy-like. Try pointing to a puppy and… good luck getting a response beyond random tail-wagging. Tails aside, the non-response is typical of non-human primates. Pointing is a cooperative activity—providing help or seeking help. If toddlers are looking for something and you point behind the couch, they identify you as a helpmate; they know you are intending to help them find the hidden thing.

If you look at culture the way Tomasello does, you find cooperation everywhere. One place is wherever teaching happens. “Teaching is present in all human societies we know of, and it is clearly not a normal activity among chimpanzees or other non-human primates,” he says. When adults are determined to see children learn, they’re ratcheting up the culture. “Children, for their part, must trust adult teaching and be ready to change behavioral strategies—in a way that chimpanzees apparently are not—as soon as they see a better one.”

Cultural conformity, too, is a variation on cooperation: There’s a uniquely human tendency to follow group fads and fashions for no apparent practical reason; it’s just that everyone is doing it (or wearing it). What Tomasello calls “normativity” is closely related. Humans self-monitor and evaluate their own thinking with respect to the standards of others; to feel you’re a member of a group is to identify with how the group thinks and behaves.

And those aren’t just normative standards. As a culture we’re always coming together to place a value on things. We’re attached to our dollar bills, but they’re valuable only because, collectively, we award them specific worth. They’re pieces of paper decorated with a presidential portrait. They’re more than that, though, by common consent.

Although chimpanzees can learn some things from others, culture doesn’t really exist for them, he says. Chimp culture, if the term even applies, is “tentative and fragile.” Human culture, in contrast, opens itself to being modified and not just to being copied; it relies both on faithful transmission across generations and the occasional adopting of novelty. Its basis in cooperation—including its emphasis on teaching, its shifting standards, and its particular way of assigning value—awards human culture a certain dynamism.

But Tomasello hardly paints a picture of everyone being everyone’s best buddy. In “The Moral Psychology of Obligation” paper, he observes that children bond first and foremost to those with whom they’re in a cooperative relationship. They have strong interactions with such partners, they protest when partners treat them badly, and they rationalize their own bad treatment of partners. Tomasello says it’s “astounding” that in this age range, children’s social behavior is affected simply by their being assigned to a “minimal group,” one with just loose supports. Once they don a green T-shirt and are told they belong to the green group, they’ll build a tight identity with the green group.

A bunch of chimps may zip out in various directions to pin down some prey. But to Tomasello, they’re individually driven, not in-group driven: “If the guy who captures it can get away with it, he’ll eat it all himself.” Among humans, when five-year-olds are given a chance to share within their in-group, they do so generously. They’re less sharing-minded with out-group members. They care a lot about their personal reputations among in-group members, and they work to cast a positive light not just on themselves but also on their closest cohort.

All of which suggests an ironic strand in Tomasello’s cooperation-centered career. When he listens to political language characterizing immigrants as invaders (or worse, as some kind of vermin), Tomasello considers what he calls “the dark side” of cooperation. Speaking in 2008, as part of a Stanford distinguished-lecturer series, he observed: “We are talking about cooperation within ‘the group,’ which is difficult to define in modern life but for most of human history corresponded simply to the couple of hundred individuals with whom one lived and interacted on a regular basis—as opposed to all those other barbarians that might be spotted from afar.”

From the time of the earliest humans, group bonds have been deepened by competition from outside: We hunt to gether in this way. They hunt together in some different way. We sure are different. That suggests a strong sense of apartness from the out-group, toward which the in-group feels no special obligation.

Still, Tomasello keeps returning to that sense of shared intentionality on a grand scale, as a deep expression of the impulse to cooperate—and, in fact, as the origin of moral conduct. In Becoming Human, he writes that children at a young age are impressed with the notion that “it is now not just about what one wants to do, but about what one ought to do.”

“Cooperative thinking and moral discourse,” as he puts it, implies the ability to accept the perspective of others, to respect the social norms of the group. Those are the prerequisites of a uniquely human social life. And so in identifying cooperation as the key human quality, as the great separator between us and our fellow primates, Tomasello is more than a philosopher-scientist. He’s also an authoritative optimist about the human condition.