“Who we are and who we become depends, in part, on whom we love,” psychologists Thomas Lewis, Fari Amini, and Richard Lannon observed in their indispensable A General Theory of Love. “To love without knowing how to love wounds the person we love,” the great Zen teacher Thich Nhat Hahn wrote. But although love has been a fixture of philosophy, ethics, and the world’s great spiritual traditions since the dawn of recorded thought, it has earned its place as a subject of science only recently, and chiefly thanks to one man — primate researcher Harry Harlow (October 31, 1905–December 6, 1981), who defied the scientific dogma of his day to unravel the psychological armature of affection, how our formative attachments shape who we become, and why love is the most primary need to be met for healthy development.

In the immeasurably captivating Love at Goon Park: Harry Harlow and the Science of Affection (public library), Pulitzer-winning writer Deborah Blum chronicles the trailblazing work and far-reaching legacy of this “chainsmoking, poetry-writing, alcoholic, impossible genius of a psychologist” — a “stubborn, scruffy, middle-aged researcher … who happens to believe that his profession is wrong and doesn’t mind saying so,” a man who “lives at the lab, dawn to dark, fueled by coffee, cigarettes, alcohol, and obsession.”

Harlow’s point of obsession and insurgency was the conviction, boldly defiant of the era’s scientific dogma, that love matters — that it is a centerpiece of our psychoemotional constitution and, as such, merits being systematically studied rather than dismissed as an irrelevant and unscientific whim. Indeed, the book is as much a biography of Harlow himself as it is of this astonishingly nascent idea, which was scientific anathema in Harlow’s heyday but has steered the course of social science and permeated popular culture in the half-century since.

Harlow used the 120 rhesus monkeys in his lab to study mother-infant attachment and how the effects of maternal separation and social isolation illuminate the nature of love. His most famous experiment devised two versions of an artificial surrogate mother for the baby monkeys — one made entirely of wire and the other, designed to be cozy and cuddly, of wire and cloth; both were internally heated to simulate the warmth of a real mother’s body. The empirical hook was that the wire-only mother held a bottle of milk, which the babies could feed on, whereas the cuddly mother offered nothing but the creaturely comfort of warmth and soft touch.

Upending decades, if not centuries, of prior theories predicated on a kind of survivalist evolutionary pragmatism, Harlow found that the baby monkeys consistently chose the cuddly mother over the feeding but cold mother. They lived latched onto the cloth mother and leaned over to the wire one nearby to take a sip of milk only when they grew hungry, but even as they did this, they remained completely attached — both literally and figuratively — to the cuddly robot. Over and over, the monkeys demonstrated that the safe embrace of comfort is more vital to their development than the steady but cold supply of sustenance.

Harlow’s findings were as profound as they are disquieting, particularly to those of us who are the product of far from perfect parenting. Recounting his central assertion — which he made on national television, further defying the norms of his profession — Blum writes:

We begin our lives with love [and] we learn human connection at home. It is the foundation upon which we build our lives — or it should be — and if the monkey or the human doesn’t learn love in infancy, he or she “may never learn to love at all.”

“If monkeys have taught us anything,” Harlow asserted in reflecting on his experiments, “it’s that you’ve got to learn how to love before you learn how to live.” Today, his findings are revered by developmental psychologists, his methods reviled by animal rights advocates in light of our radically different norms of primate research, and his legacy as enormous and messy as the subject of his study.

To appreciate just how radical a departure from the status quo of science Harlow’s theories were, we must turn to language — for, as the poet Elizabeth Alexander memorably observed, “we live in the word.” Harlow’s work was his life, and he refused to live in limiting language defined by dogma. Blum captures his irreverent genius:

Professor Harlow has already been asked to correct his language: He’s been instructed on the correct term for a close relationship. Why can’t he just say “proximity” like everyone else? Somehow the word “love” just keeps springing to his lips when he talks about parents and children, friends and partners. He’s been known to lose his temper when discussing it. “Perhaps all you’ve known in life is proximity,” he once snapped at a visitor to his lab at the University of Wisconsin in Madison. “I thank God I’ve known more.” […] Who wouldn’t believe that love was, at its best, a safe harbor — a parent’s arm scooping up a frightened child, holding it heart to heart? It’s hard to believe, in retrospect, how many powerful scientists opposed this idea.

Blum points to one researcher emblematic of the era — psychologist John B. Watson, president of the American Psychological Association, who believed that emotion was a moral weakness to be controlled and considered love, the most intense and messiest of the emotions, a supreme offender the corrupting effects of which should be restrained as early as possible. In a particularly spirited passage, he admonished:

When you are tempted to pet your child remember that mother love is a dangerous instrument… Once a child’s character has been spoiled by bad handling, which can be done in a few days, who can say that the damage is ever repaired?

In the midst of this professional climate, Harlow chose “to stand on behalf of that improbable, unreliable, elusive emotion called love” and helmed a quiet, monumental revolution. It’s astonishing to consider that getting science to heed a truth this elemental and intuitive — that love is central to our experience of being human — should necessitate nothing short of a revolution, and yet it very much did. Like any revolution, it required the collusion of kindred spirits working together against an enormous tide of pushback.

Among those confederates was the English psychologist John Bowlby, who pioneered attachment theory and the idea that the fulfillment of physical needs like sustenance and shelter is a secondary drive in the parent-child relationship — love is the primary one. Blum explains:

What attachment theory essentially says is that being loved matters — and, more than that, it matters who loves us and whom we love in return. It’s not just a matter of the warm body holding the bottle; it’s not object love at all; we love specific people and we need them to love us back. And in the case of the child’s tie to the mother, it matters that the mother loves that baby and that the baby knows it. When you are a very small child, love needs to be as tangible as warm arms around you and as audible as the lull of a gentle voice at night.

Bowlby’s work was instrumental, but there was one other essential building block in the architecture of Harlow’s quiet revolution — the work of a New York physician named William Goldfarb, who made the unnerving discovery that parental affection exerts a strong influence on the child’s IQ. Preoccupied with the fate of children in New York’s Jewish orphanages and foundling homes, Goldfarb had grown concerned that social isolation was damaging their intellectual development. To test his theory, he measured their performance on IQ tests and compared it to that of children in foster homes.

Foundling children were often the result of unwanted pregnancies by educated women of high social class, whereas foster kids came from less credentialed backgrounds and ended up with their new parents after the displacement or death of their biological parents. Since existing theories held that genes were the greatest predictor of intelligence, it was expected that the foundlings would perform better than the foster kids on IQ tests. But Goldfarb found the opposite. Love and intelligence, it turned out, were far more strongly correlated than genetics and intelligence.

Blum writes:

The foundlings were less determined, less interested, less willing to explore… One problem was that no one was interested in them, [Goldfarb] said. The caretakers seemed indifferent. But was that surprising? Goldfarb asked. Is an adult ever interested in a child who doesn’t stir his heart? An odd kind of chicken or egg issue underlies that query. Does affection for another person create interest in him or does interest lead to affection? When it came to the foundlings, Goldfarb had an idea that interest and affection twined together, tight as a rope, almost inseparably. All of us, even as babies, are a bundle of feelings and desires, he said. Our positive emotions grow best in an interactive sense, fostered by how we react to others and how they respond to us. A baby, a child, even an adult, needs at least one person interested and responsive. We grow best in soil cultivated by someone who thinks we matter.

This brings us back to Harlow. Building on these compelling but fragmentary insights, he advanced a robust and holistic theory of how profoundly our formative interactions and attachments shape our destiny, and then he set out to derive definitive evidence. To prove the importance of parental affection, he would demonstrate the effects of its absence and, even more dramatically, of its opposite.

Blum chronicles the clever, if cruel, twist Harlow put on his wire-mother experiments:

The lab team built what Harry called evil or “monster” mothers. There were four of them and they were cloth moms gone crazy. All of them had a soft-centered body for cuddling. But they were, all of them, booby traps. One was a “shaking” mother who rocked so violently that, Harry said, the teeth and bones of the infant chattered in unison. The second was an air-blast mother. She blew compressed air against the infant with such force that the baby looked, Harry said, as if it would be denuded. The third had an embedded steel frame that, on schedule or demand, would fling forward and hurl the infant monkey off the mother’s body. The fourth monster mother had brass spikes (blunt-tipped) tucked into her chest; these would suddenly, unexpectedly push against the clinging child.

What Harlow found was both heartbreaking and heartbreakingly understandable — rather than fleeing from the monstrous mothers, the babies tried harder to earn their affection. After every violent repulsion, they returned to the monsters, only to cling more tightly and coo more beseechingly, “expressing faith and love as if all were forgiven,” as Harlow put it.

Blum encapsulates the profound implications, revealing love to be a kind of primal addiction:

No experiment could have better demonstrated the depth and strength of a baby’s addiction for her parent. Or how terrifyingly vulnerable that addiction makes a child. These little monkeys would be frightened away by brass spike mom — and yet it was she they turned to for comfort. They had to; she was what they had. Here indeed was further evidence of that haven-of-security effect, for better and for worse. It doesn’t always keep you safe. If your mother is your only source of comfort and your mother is evil, what choices are left you in seeking safe harbor? No choice except to keep trying to cast anchor in the only harbor available. Harry and his team would find the same pattern when real mother monkeys were rejecting or abusive. The scientists marveled at “the desperate efforts the babies made to contact their mothers. No matter how abusive the mothers were, the babies persisted in returning.” They returned more often, they reached and clung and coaxed far more frequently than the children of normal mothers. The infants were so preoccupied with engaging their mothers that they had little energy for friends. The clinging babies’ energy was directed into their attempts to coax a little affection out at home. Sometimes the real monkey mothers did respond, gradually, more kindly. But while trying to reach mother, the little monkeys never had time to reach anyone else.

Harlow’s findings ushered in a tidal wave of change in psychology and instituted love as a proper and central subject in the study of human development. Generations of psychologists built on his work, including many of Harlow’s own students.

Among them was Steve Suomi, director of the National Institutes of Health lab of comparative ethology, who became interested in the interplay of nature and nurture in emotional development. In one ingenious experiment, he divided a sample of baby monkeys into two groups. Some remained with their biological mothers, who were selected to be unaffectionate and inattentive, while others were raised by what Suomi called “supermoms” — caretakers selected for their exceedingly affectionate nurturing style. Both groups of mothers cared for a variety of babies, including some naturally anxious and nervous ones.

Suomi found that the baby monkeys developed optimally under the care of the most loving mother, regardless of their biological connection. The effects were most dramatic on the nervous babies — with an unwaveringly affectionate mother, they grew calmer and became nurturers themselves, but with a neurotic mother, they grew even more nervous, fearful, and anxious to explore their environment.

Blum writes:

There are several reminders in that elegant NIH experiment: that we need not grow up to be our mothers; that we may not want to; that it’s not easy to change. And that it may be unfair to load all our expectations and needs onto one parent, anyway. With the best intentions in the world, one person may not be able — or intended — to give a child everything he or she needs. The extended family, even the right child care provider may be exactly what’s needed.

As it turns out, this is true not only of parent-child relationships but of all intimate attachments — Esther Perel has written elegantly about the comparable perils of placing all of one’s expectations on one’s romantic partner. But since we seek out romantic partners largely on the basis of emotional patterning laid out in childhood, even this can be traced to Harlow’s legacy.

Blum encapsulates the heart of his work and its enduring implications:

There is no requirement for angelic perfection in parenting. The requirement is just to stay in there. Harry’s research tells us that love is work. So do all the studies that follow. The nature of love is about paying attention to the people who matter, about still giving when you are too tired to give. Be a mother who listens, a father who cuddles, a friend who calls back, a helping neighbor, a loving child. That emphasis on love in our everyday lives may be the best of that quiet revolution in psychology, the one that changed the way we think about love and relationship almost without our noticing that had happened. We take for granted now that parents should hug their children, that relationships are worth the time, that taking care of each other is part of the good life. It is such a good foundation that it’s almost astonishing to consider how recent it is. For that foundation under our feet we owe a debt to Harry Harlow and to all the scientists who believed and worked toward a psychology of the heart. At the end, in Harry’s handiwork, there’s nothing sentimental about love, no sunlit clouds and glory notes—it’s a substantial, earthbound connection, grounded in effort, kindness, and decency. Learning to love, Harry liked to say, is really about learning to live. Perhaps everyday affection seems a small facet of love. Perhaps, though, it is the modest, steady responses that see us through day after day, that stretch into a life of close and loving relationships. Or, as Harry Harlow wrote to a friend, “Perhaps one should always be modest when talking about love.”

Love at Goon Park is a tremendously pleasurable and revelatory read in its totality. Complement it with young Barack Obama on what his mother taught him about love, Iris Murdoch on how love gives meaning to human existence, and Erich Fromm on what is keeping us from mastering the art of loving.