Quiet: The Power of Introverts in a World That Can't Stop Talking - Susan Cain (2012)



Nature, Nurture, and the Orchid Hypothesis

Some people are more certain of everything than I am of anything.
—ROBERT RUBIN, In an Uncertain World


It’s 2:00 a.m., I can’t sleep, and I want to die.

I’m not normally the suicidal type, but this is the night before a big speech, and my mind races with horrifying what-if propositions. What if my mouth dries up and I can’t get any words out? What if I bore the audience? What if I throw up onstage?

My boyfriend (now my husband), Ken, watches me toss and turn. He’s bewildered by my distress. A former UN peacekeeper, he once was ambushed in Somalia, yet I don’t think he felt as scared then as I do now.

“Try to think of happy things,” he says, caressing my forehead.

I stare at the ceiling, tears welling. What happy things? Who could be happy in a world of podiums and microphones?

“There are a billion people in China who don’t give a rat’s ass about your speech,” Ken offers sympathetically.

This helps, for approximately five seconds. I turn over and watch the alarm clock. Finally it’s six thirty. At least the worst part, the night-before part, is over; this time tomorrow, I’ll be free. But first I have to get through today. I dress grimly and put on a coat. Ken hands me a sports water bottle filled with Baileys Irish Cream. I’m not a big drinker, but I like Baileys because it tastes like a chocolate milkshake. “Drink this fifteen minutes before you go on,” he says, kissing me good-bye.

I take the elevator downstairs and settle into the car that waits to ferry me to my destination, a big corporate headquarters in suburban New Jersey. The drive gives me plenty of time to wonder how I allowed myself to get into this situation. I recently left my job as a Wall Street lawyer to start my own consulting firm. Mostly I’ve worked one-on-one or in small groups, which feels comfortable. But when an acquaintance who is general counsel at a big media company asked me to run a seminar for his entire executive team, I agreed—enthusiastically, even!—for reasons I can’t fathom now. I find myself praying for calamity—a flood or a small earthquake, maybe—anything so I don’t have to go through with this. Then I feel guilty for involving the rest of the city in my drama.

The car pulls up at the client’s office and I step out, trying to project the peppy self-assurance of a successful consultant. The event organizer escorts me to the auditorium. I ask for directions to the bathroom, and, in the privacy of the stall, gulp from the water bottle. For a few moments I stand still, waiting for the alcohol to work its magic. But nothing happens—I’m still terrified. Maybe I should take another swig. No, it’s only nine in the morning—what if they smell the liquor on my breath? I reapply my lipstick and make my way back to the event room, where I arrange my notecards at the podium as the room fills with important-looking businesspeople. Whatever you do, try not to vomit, I tell myself.

Some of the executives glance up at me, but most of them stare fixedly at their BlackBerrys. Clearly, I’m taking them away from very pressing work. How am I going to hold their attention long enough for them to stop pounding out urgent communiqués into their tiny typewriters? I vow, right then and there, that I will never make another speech.

Well, since then I’ve given plenty of them. I haven’t completely overcome my anxiety, but over the years I’ve discovered strategies that can help anyone with stage fright who needs to speak in public. More about that in chapter 5.

In the meantime, I’ve told you my tale of abject terror because it lies at the heart of some of my most urgent questions about introversion. On some deep level, my fear of public speaking seems connected to other aspects of my personality that I appreciate, especially my love of all things gentle and cerebral. This strikes me as a not-uncommon constellation of traits. But are they truly connected, and if so, how? Are they the result of “nurture”—the way I was raised? Both of my parents are soft-spoken, reflective types; my mother hates public speaking too. Or are they my “nature”—something deep in my genetic makeup?

I’ve been puzzling over these questions for my entire adult life. Fortunately, so have researchers at Harvard, where scientists are probing the human brain in an attempt to discover the biological origins of human temperament.

One such scientist is an eighty-two-year-old man named Jerome Kagan, one of the great developmental psychologists of the twentieth century. Kagan devoted his career to studying the emotional and cognitive development of children. In a series of groundbreaking longitudinal studies, he followed children from infancy through adolescence, documenting their physiologies and personalities along the way. Longitudinal studies like these are time-consuming, expensive, and therefore rare—but when they pay off, as Kagan’s did, they pay off big.

For one of those studies, launched in 1989 and still ongoing, Professor Kagan and his team gathered five hundred four-month-old infants in his Laboratory for Child Development at Harvard, predicting they’d be able to tell, on the strength of a forty-five-minute evaluation, which babies were more likely to turn into introverts or extroverts. If you’ve seen a four-month-old baby lately, this may seem an audacious claim. But Kagan had been studying temperament for a long time, and he had a theory.

Kagan and his team exposed the four-month-olds to a carefully chosen set of new experiences. The infants heard tape-recorded voices and balloons popping, saw colorful mobiles dance before their eyes, and inhaled the scent of alcohol on cotton swabs. They had wildly varying reactions to the new stimuli. About 20 percent cried lustily and pumped their arms and legs. Kagan called this group “high-reactive.” About 40 percent stayed quiet and placid, moving their arms or legs occasionally, but without all the dramatic limb-pumping. This group Kagan called “low-reactive.” The remaining 40 percent fell between these two extremes. In a startlingly counterintuitive hypothesis, Kagan predicted that it was the infants in the high-reactive group—the lusty arm-pumpers—who were most likely to grow into quiet teenagers.

When they were two, four, seven, and eleven years old, many of the children returned to Kagan’s lab for follow-up testing of their reactions to new people and events. At the age of two, the children met a lady wearing a gas mask and a lab coat, a man dressed in a clown costume, and a radio-controlled robot. At seven, they were asked to play with kids they’d never met before. At eleven, an unfamiliar adult interviewed them about their personal lives. Kagan’s team observed how the children reacted to these strange situations, noting their body language and recording how often and spontaneously they laughed, talked, and smiled. They also interviewed the kids and their parents about what the children were like outside the laboratory. Did they prefer one or two close friends to a merry band? Did they like visiting new places? Were they risk-takers or were they more cautious? Did they consider themselves shy or bold?

Many of the children turned out exactly as Kagan had expected. The high-reactive infants, the 20 percent who’d hollered at the mobiles bobbing above their heads, were more likely to have developed serious, careful personalities. The low-reactive infants—the quiet ones—were more likely to have become relaxed and confident types. High and low reactivity tended to correspond, in other words, to introversion and extroversion. As Kagan mused in his 1998 book, Galen’s Prophecy, “Carl Jung’s descriptions of the introvert and extrovert, written over seventy-five years ago, apply with uncanny accuracy to a proportion of our high- and low-reactive adolescents.”

Kagan describes two of those adolescents—reserved Tom and extroverted Ralph—and the differences between the two are striking. Tom, who was unusually shy as a child, is good at school, watchful and quiet, devoted to his girlfriend and parents, prone to worry, and loves learning on his own and thinking about intellectual problems. He plans to be a scientist. “Like … other famous introverts who were shy children,” writes Kagan, comparing Tom to T. S. Eliot and the mathematician-philosopher Alfred North Whitehead, Tom “has chosen a life of the mind.”

Ralph, in contrast, is relaxed and self-assured. He engages the interviewer from Kagan’s team as a peer, not as an authority figure twenty-five years his senior. Though Ralph is very bright, he recently failed his English and science classes because he’d been goofing around. But nothing much bothers Ralph. He admits his flaws cheerfully.

Psychologists often discuss the difference between “temperament” and “personality.” Temperament refers to inborn, biologically based behavioral and emotional patterns that are observable in infancy and early childhood; personality is the complex brew that emerges after cultural influence and personal experience are thrown into the mix. Some say that temperament is the foundation, and personality is the building. Kagan’s work helped link certain infant temperaments with adolescent personality styles like those of Tom and Ralph.

But how did Kagan know that the arm-thrashing infants would likely turn into cautious, reflective teens like Tom, or that the quiet babies were more likely to become forthright, too-cool-for-school Ralphs? The answer lies in their physiologies.

In addition to observing the children’s behaviors in strange situations, Kagan’s team measured their heart rates, blood pressure, finger temperature, and other properties of the nervous system. Kagan chose these measures because they’re believed to be controlled by a potent organ inside the brain called the amygdala. The amygdala is located deep in the limbic system, an ancient brain network found even in primitive animals like mice and rats. This network—sometimes called the “emotional brain”—underlies many of the basic instincts we share with these animals, such as appetite, sex drive, and fear.

The amygdala serves as the brain’s emotional switchboard, receiving information from the senses and then signaling the rest of the brain and nervous system how to respond. One of its functions is to instantly detect new or threatening things in the environment—from an airborne Frisbee to a hissing serpent—and send rapid-fire signals through the body that trigger the fight-or-flight response. When the Frisbee looks like it’s headed straight for your nose, it’s your amygdala that tells you to duck. When the rattlesnake prepares to bite, it’s the amygdala that makes sure you run.

Kagan hypothesized that infants born with an especially excitable amygdala would wiggle and howl when shown unfamiliar objects—and grow up to be children who were more likely to feel vigilant when meeting new people. And this is just what he found. In other words, the four-month-olds who thrashed their arms like punk rockers did so not because they were extroverts in the making, but because their little bodies reacted strongly—they were “high-reactive”—to new sights, sounds, and smells. The quiet infants were silent not because they were future introverts—just the opposite—but because they had nervous systems that were unmoved by novelty.

The more reactive a child’s amygdala, the higher his heart rate is likely to be, the more widely dilated his eyes, the tighter his vocal cords, the more cortisol (a stress hormone) in his saliva—the more jangled he’s likely to feelwhen he confronts something new and stimulating. As high-reactive infants grow up, they continue to confront the unknown in many different contexts, from visiting an amusement park for the first time to meeting new classmates on the first day of kindergarten. We tend to notice most a child’s reaction to unfamiliar people—how does he behave on the first day of school? Does she seem uncertain at birthday parties full of kids she doesn’t know? But what we’re really observing is a child’s sensitivity to novelty in general, not just to people.

High- and low-reactivity are probably not the only biological routes to introversion and extroversion. There are plenty of introverts who do not have the sensitivity of a classic high-reactive, and a small percentage of high-reactives grow up to be extroverts. Still, Kagan’s decades-long series of discoveries mark a dramatic breakthrough in our understanding of these personality styles—including the value judgments we make. Extroverts are sometimes credited with being “pro-social”—meaning caring about others—and introverts disparaged as people who don’t like people. But the reactions of the infants in Kagan’s tests had nothing to do with people. These babies were shouting (or not shouting) over Q-tips. They were pumping their limbs (or staying calm) in response to popping balloons. The high-reactive babies were not misanthropes in the making; they were simply sensitive to their environments.

Indeed, the sensitivity of these children’s nervous systems seems to be linked not only to noticing scary things, but to noticing in general. High-reactive children pay what one psychologist calls “alert attention” to people and things. They literally use more eye movements than others to compare choices before making a decision. It’s as if they process more deeply—sometimes consciously, sometimes not—the information they take in about the world. In one early series of studies, Kagan asked a group of first-graders to play a visual matching game. Each child was shown a picture of a teddy bear sitting on a chair, alongside six other similar pictures, only one of which was an exact match. The high-reactive children spent more time than others considering all the alternatives, and were more likely to make the right choice. When Kagan asked these same kids to play word games, he found that they also read more accurately than impulsive children did.

High-reactive kids also tend to think and feel deeply about what they’ve noticed, and to bring an extra degree of nuance to everyday experiences. This can be expressed in many different ways. If the child is socially oriented, she may spend a lot of time pondering her observations of others—why Jason didn’t want to share his toys today, why Mary got so mad at Nicholas when he bumped into her accidentally. If he has a particular interest—in solving puzzles, making art, building sand castles—he’ll often concentrate with unusual intensity. If a high-reactive toddler breaks another child’s toy by mistake, studies show, she often experiences a more intense mix of guilt and sorrow than a lower-reactive child would. All kids notice their environments and feel emotions, of course, but high-reactive kids seem to see and feel things more. If you ask a high-reactive seven-year-old how a group of kids should share a coveted toy, writes the science journalist Winifred Gallagher, he’ll tend to come up with sophisticated strategies like “Alphabetize their last names, and let the person closest to A go first.”

“Putting theory into practice is hard for them,” writes Gallagher, “because their sensitive natures and elaborate schemes are unsuited to the heterogeneous rigors of the schoolyard.” Yet as we’ll see in the chapters to come, these traits—alertness, sensitivity to nuance, complex emotionality—turn out to be highly underrated powers.

Kagan has given us painstakingly documented evidence that high reactivity is one biological basis of introversion (we’ll explore another likely route in chapter 7), but his findings are powerful in part because they confirm what we’ve sensed all along. Some of Kagan’s studies even venture into the realm of cultural myth. For example, he believes, based on his data, that high reactivity is associated with physical traits such as blue eyes, allergies, and hay fever, and that high-reactive men are more likely than others to have a thin body and narrow face. Such conclusions are speculative and call to mind the nineteenth-century practice of divining a man’s soul from the shape of his skull. But whether or not they turn out to be accurate, it’s interesting that these are just the physical characteristics we give fictional characters when we want to suggest that they’re quiet, introverted, cerebral. It’s as if these physiological tendencies are buried deep in our cultural unconscious.

Take Disney movies, for example: Kagan and his colleagues speculate that Disney animators unconsciously understood high reactivity when they drew sensitive figures like Cinderella, Pinocchio, and Dopey with blue eyes, and brasher characters like Cinderella’s stepsisters, Grumpy, and Peter Pan with darker eyes. In many books, Hollywood films, and TV shows, too, the stock character of a reedy, nose-blowing young man is shorthand for the hapless but thoughtful kid who gets good grades, is a bit overwhelmed by the social whirl, and is talented at introspective activities like poetry or astrophysics. (Think Ethan Hawke in Dead Poets Society.) Kagan even speculates that some men prefer women with fair skin and blue eyes because they unconsciously code them as sensitive.

Other studies of personality also support the premise that extroversion and introversion are physiologically, even genetically, based. One of the most common ways of untangling nature from nurture is to compare the personality traits of identical and fraternal twins. Identical twins develop from a single fertilized egg and therefore have exactly the same genes, while fraternal twins come from separate eggs and share only 50 percent of their genes on average. So if you measure introversion or extroversion levels in pairs of twins and find more correlation in identical twins than in fraternal pairs—which scientists do, in study after study, even of twins raised in separate households—you can reasonably conclude that the trait has some genetic basis.

None of these studies is perfect, but the results have consistently suggested that introversion and extroversion, like other major personality traits such as agreeableness and conscientiousness, are about 40 to 50 percent heritable.

But are biological explanations for introversion wholly satisfying? When I first read Kagan’s book Galen’s Prophecy, I was so excited that I couldn’t sleep. Here, inside these pages, were my friends, my family, myself—all of humanity, in fact!—neatly sorted through the prism of a quiescent nervous system versus a reactive one. It was as if centuries of philosophical inquiry into the mystery of human personality had led to this shining moment of scientific clarity. There was an easy answer to the nature-nurture question after all—we are born with prepackaged temperaments that powerfully shape our adult personalities.

But it couldn’t be that simple—could it? Can we really reduce an introverted or extroverted personality to the nervous system its owner was born with? I would guess that I inherited a high-reactive nervous system, but my mother insists I was an easy baby, not the kind to kick and wail over a popped balloon. I’m prone to wild flights of self-doubt, but I also have a deep well of courage in my own convictions. I feel horribly uncomfortable on my first day in a foreign city, but I love to travel. I was shy as a child, but have outgrown the worst of it. Furthermore, I don’t think these contradictions are so unusual; many people have dissonant aspects to their personalities. And people change profoundly over time, don’t they? What about free will—do we have no control over who we are, and whom we become?

I decided to track down Professor Kagan to ask him these questions in person. I felt drawn to him not only because his research findings were so compelling, but also because of what he represents in the great nature-nurture debate. He’d launched his career in 1954 staunchly on the side of nurture, a view in step with the scientific establishment of the day. Back then, the idea of inborn temperament was political dynamite, evoking the specter of Nazi eugenics and white supremacism. By contrast, the notion of children as blank slates for whom anything was possible appealed to a nation built on democracy.

But Kagan had changed his mind along the way. “I have been dragged, kicking and screaming, by my data,” he says now, “to acknowledge that temperament is more powerful than I thought and wish to believe.” The publication of his early findings on high-reactive children in Science magazine in 1988 helped to legitimize the idea of inborn temperament, partly because his “nurturist” reputation was so strong.

If anyone could help me untangle the nature-nurture question, I hoped, it was Jerry Kagan.

Kagan ushers me inside his office in Harvard’s William James Hall, surveying me unblinkingly as I sit down: not unkind, but definitely discerning. I had imagined him as a gentle, white-lab-coated scientist in a cartoon, pouring chemicals from one test tube to another until—poof! Now, Susan, you know exactly who you are. But this isn’t the mild-mannered old professor I’d imagined. Ironically for a scientist whose books are infused with humanism and who describes himself as having been an anxious, easily frightened boy, I find him downright intimidating. I kick off our interview by asking a background question whose premise he disagrees with. “No, no, no!” he thunders, as if I weren’t sitting just across from him.

The high-reactive side of my personality kicks into full gear. I’m always soft-spoken, but now I have to force my voice to come out louder than a whisper (on the tape recording of our conversation, Kagan’s voice sounds booming and declamatory, mine much quieter). I’m aware that I’m holding my torso tensely, one of the telltale signs of the high-reactive. It feels strange to know that Kagan must be observing this too—he says as much, nodding at me as he notes that many high-reactives become writers or pick other intellectual vocations where “you’re in charge: you close the door, pull down the shades and do your work. You’re protected from encountering unexpected things.” (Those from less educated backgrounds tend to become file clerks and truck drivers, he says, for the same reasons.)

I mention a little girl I know who is “slow to warm up.” She studies new people rather than greeting them; her family goes to the beach every weekend, but it takes her ages to dip a toe into the surf. A classic high-reactive, I remark.

“No!” Kagan exclaims. “Every behavior has more than one cause. Don’t ever forget that! For every child who’s slow to warm up, yes, there will be statistically more high-reactives, but you can be slow to warm up because of how you spent the first three and a half years of your life! When writers and journalists talk, they want to see a one-to-one relationship—one behavior, one cause. But it’s really important that you see, for behaviors like slow-to-warm-up, shyness, impulsivity, there are many routes to that.”

He reels off examples of environmental factors that could produce an introverted personality independently of, or in concert with, a reactive nervous system: A child might enjoy having new ideas about the world, say, so she spends a lot of time inside her head. Or health problems might direct a child inward, to what’s going on inside his body.

My fear of public speaking might be equally complex. Do I dread it because I’m a high-reactive introvert? Maybe not. Some high-reactives love public speaking and performing, and plenty of extroverts have stage fright; public speaking is the number-one fear in America, far more common than the fear of death. Public speaking phobia has many causes, including early childhood setbacks, that have to do with our unique personal histories, not inborn temperament.

In fact, public speaking anxiety may be primal and quintessentially human, not limited to those of us born with a high-reactive nervous system. One theory, based on the writings of the sociobiologist E. O. Wilson, holds that when our ancestors lived on the savannah, being watched intently meant only one thing: a wild animal was stalking us. And when we think we’re about to be eaten, do we stand tall and hold forth confidently? No. We run. In other words, hundreds of thousands of years of evolution urge us to get the hell off the stage, where we can mistake the gaze of the spectators for the glint in a predator’s eye. Yet the audience expects not only that we’ll stay put, but that we’ll act relaxed and assured. This conflict between biology and protocol is one reason that speechmaking can be so fraught. It’s also why exhortations to imagine the audience in the nude don’t help nervous speakers; naked lions are just as dangerous as elegantly dressed ones.

But even though all human beings may be prone to mistaking audience members for predators, each of us has a different threshold for triggering the fight-or-flight response. How threateningly must the eyes of the audience members narrow before you feel they’re about to pounce? Does it happen before you’ve even stepped onstage, or does it take a few really good hecklers to trigger that adrenaline rush? You can see how a highly sensitive amygdala would make you more susceptible to frowns and bored sighs and people who check their BlackBerrys while you’re in mid-sentence. And indeed, studies do show that introverts are significantly more likely than extroverts to fear public speaking.

Kagan tells me about the time he watched a fellow scientist give a wonderful talk at a conference. Afterward, the speaker asked if they could have lunch. Kagan agreed, and the scientist proceeded to tell him that he gives lectures every month and, despite his capable stage persona, is terrified each time. Reading Kagan’s work had had a big impact on him, however.

“You changed my life,” he told Kagan. “All this time I’ve been blaming my mother, but now I think I’m a high-reactive.”

So am I introverted because I inherited my parents’ high reactivity, copied their behaviors, or both? Remember that the heritability statistics derived from twin studies show that introversion-extroversion is only 40 to 50 percent heritable. This means that, in a group of people, on average half of the variability in introversion-extroversion is caused by genetic factors. To make things even more complex, there are probably many genes at work, and Kagan’s framework of high reactivity is likely one of many physiological routes to introversion. Also, averages are tricky. A heritability rate of 50 percent doesn’t necessarily mean that my introversion is 50 percent inherited from my parents, or that half of the difference in extroversion between my best friend and me is genetic. One hundred percent of my introversion might come from genes, or none at all—or more likely some unfathomable combination of genes and experience. To ask whether it’s nature or nurture, says Kagan, is like asking whether a blizzard is caused by temperature or humidity. It’s the intricate interaction between the two that makes us who we are.

So perhaps I’ve been asking the wrong question. Maybe the mystery of what percent of personality is nature and what percent nurture is less important than the question of how your inborn temperament interacts with the environment and with your own free will. To what degree is temperament destiny?

On the one hand, according to the theory of gene-environment interaction, people who inherit certain traits tend to seek out life experiences that reinforce those characteristics. The most low-reactive kids, for example, court danger from the time they’re toddlers, so that by the time they grow up they don’t bat an eye at grown-up-sized risks. They “climb a few fences, become desensitized, and climb up on the roof,” the late psychologist David Lykken once explained in an Atlantic article. “They’ll have all sorts of experiences that other kids won’t. Chuck Yeager (the first pilot to break the sound barrier) could step down from the belly of the bomber into the rocketship and push the button not because he was born with that difference between him and me, but because for the previous thirty years his temperament impelled him to work his way up from climbing trees through increasing degrees of danger and excitement.”

Conversely, high-reactive children may be more likely to develop into artists and writers and scientists and thinkers because their aversion to novelty causes them to spend time inside the familiar—and intellectually fertile—environment of their own heads. “The university is filled with introverts,” observes the psychologist Jerry Miller, director of the Center for the Child and the Family at the University of Michigan. “The stereotype of the university professor is accurate for so many people on campus. They like to read; for them there’s nothing more exciting than ideas. And some of this has to do with how they spent their time when they were growing up. If you spend a lot of time charging around, then you have less time for reading and learning. There’s only so much time in your life.”

On the other hand, there is also a wide range of possible outcomes for each temperament. Low-reactive, extroverted children, if raised by attentive families in safe environments, can grow up to be energetic achievers with big personalities—the Richard Bransons and Oprahs of this world. But give those same children negligent caregivers or a bad neighborhood, say some psychologists, and they can turn into bullies, juvenile delinquents, or criminals. Lykken has controversially called psychopaths and heroes “twigs on the same genetic branch.”

Consider the mechanism by which kids acquire their sense of right and wrong. Many psychologists believe that children develop a conscience when they do something inappropriate and are rebuked by their caregivers. Disapproval makes them feel anxious, and since anxiety is unpleasant, they learn to steer clear of antisocial behavior. This is known as internalizing their parents’ standards of conduct, and its core is anxiety.

But what if some kids are less prone to anxiety than others, as is true of extremely low-reactive kids? Often the best way to teach these children values is to give them positive role models and to channel their fearlessness into productive activities. A low-reactive child on an ice-hockey team enjoys his peers’ esteem when he charges at his opponents with a lowered shoulder, which is a “legal” move. But if he goes too far, raises his elbow, and gives another guy a concussion, he lands in the penalty box. Over time he learns to use his appetite for risk and assertiveness wisely.

Now imagine this same child growing up in a dangerous neighborhood with few organized sports or other constructive channels for his boldness. You can see how he might fall into delinquency. It may be that some disadvantaged kids who get into trouble suffer not solely from poverty or neglect, say those who hold this view, but also from the tragedy of a bold and exuberant temperament deprived of healthy outlets.

The destinies of the most high-reactive kids are also influenced by the world around them—perhaps even more so than for the average child, according to a groundbreaking new theory dubbed “the orchid hypothesis” by David Dobbs in a wonderful article in The Atlantic. This theory holds that many children are like dandelions, able to thrive in just about any environment. But others, including the high-reactive types that Kagan studied, are more like orchids: they wilt easily, but under the right conditions can grow strong and magnificent.

According to Jay Belsky, a leading proponent of this view and a psychology professor and child care expert at the University of London, the reactivity of these kids’ nervous systems makes them quickly overwhelmed by childhood adversity, but also able to benefit from a nurturing environment more than other children do. In other words, orchid children are more strongly affected by all experience, both positive and negative.

Scientists have known for a while that high-reactive temperaments come with risk factors. These kids are especially vulnerable to challenges like marital tension, a parent’s death, or abuse. They’re more likely than their peers to react to these events with depression, anxiety, and shyness. Indeed, about a quarter of Kagan’s high-reactive kids suffer from some degree of the condition known as “social anxiety disorder,” a chronic and disabling form of shyness.

What scientists haven’t realized until recently is that these risk factors have an upside. In other words, the sensitivities and the strengths are a package deal. High-reactive kids who enjoy good parenting, child care, and a stable home environment tend to have fewer emotional problems and more social skills than their lower-reactive peers, studies show. Often they’re exceedingly empathic, caring, and cooperative. They work well with others. They are kind, conscientious, and easily disturbed by cruelty, injustice, and irresponsibility. They’re successful at the things that matter to them. They don’t necessarily turn into class presidents or stars of the school play, Belsky told me, though this can happen, too: “For some it’s becoming the leader of their class. For others it takes the form of doing well academically or being well-liked.”

The upsides of the high-reactive temperament have been documented in exciting research that scientists are only now beginning to pull together. One of the most interesting findings, also reported in Dobbs’s Atlantic article, comes from the world of rhesus monkeys, a species that shares about 95 percent of its DNA with humans and has elaborate social structures that resemble our own.

In these monkeys as well as in humans, a gene known as the serotonin-transporter (SERT) gene, or 5-HTTLPR, helps to regulate the processing of serotonin, a neurotransmitter that affects mood. A particular variation, or allele, of this gene, sometimes referred to as the “short” allele, is thought to be associated with high reactivity and introversion, as well as a heightened risk of depression in humans who have had difficult lives. When baby monkeys with a similar allele were subjected to stress—in one experiment they were taken from their mothers and raised as orphans—they processed serotonin less efficiently (a risk factor for depression and anxiety) than monkeys with the long allele who endured similar privations. But young monkeys with the same risky genetic profile who were raised by nurturing mothers did as well as or better than their long-allele brethren—even those raised in similarly secure environments—at key social tasks, like finding playmates, building alliances, and handling conflicts. They often became leaders of their troops. They also processed serotonin more efficiently.

Stephen Suomi, the scientist who conducted these studies, has speculated that these high-reactive monkeys owed their success to the enormous amounts of time they spent watching rather than participating in the group, absorbing on a deep level the laws of social dynamics. (This is a hypothesis that might ring true to parents whose high-reactive children hover observantly on the edges of their peer group, sometimes for weeks or months, before edging successfully inside.)

Studies in humans have found that adolescent girls with the short allele of the SERT gene are 20 percent more likely to be depressed than long-allele girls when exposed to stressful family environments, but 25 percent less likely to be depressed when raised in stable homes. Similarly, short allele adults have been shown to have more anxiety in the evening than others when they’ve had stressful days, but less anxiety on calm days. High-reactive four-year-olds give more pro-social responses than other children when presented with moral dilemmas—but this difference remains at age five only if their mothers used gentle, not harsh, discipline. High-reactive children raised in supportive environments are even more resistant than other kids to the common cold and other respiratory illnesses, but get sick more easily if they’re raised in stressful conditions. The short allele of the SERT gene is also associated with higher performance on a wide range of cognitive tasks.

These findings are so dramatic that it’s remarkable no one arrived at them until recently. Remarkable, but perhaps not surprising. Psychologists are trained to heal, so their research naturally focuses on problems and pathology. “It is almost as if, metaphorically speaking, sailors are so busy—and wisely—looking under the water line for extensions of icebergs that could sink their ship,” writes Belsky, “that they fail to appreciate that by climbing on top of the iceberg it might prove possible to chart a clear passage through the ice-laden sea.”

The parents of high-reactive children are exceedingly lucky, Belsky told me. “The time and effort they invest will actually make a difference. Instead of seeing these kids as vulnerable to adversity, parents should see them as malleable—for worse, but also for better.” He describes eloquently a high-reactive child’s ideal parent: someone who “can read your cues and respect your individuality; is warm and firm in placing demands on you without being harsh or hostile; promotes curiosity, academic achievement, delayed gratification, and self-control; and is not harsh, neglectful, or inconsistent.” This advice is terrific for all parents, of course, but it’s crucial for raising a high-reactive child. (If you think your child might be high-reactive, you’re probably already asking yourself what else you can do to cultivate your son or daughter. Chapter 11 has some answers.)

But even orchid children can withstand some adversity, Belsky says. Take divorce. In general, it will disrupt orchid kids more than others: “If the parents squabble a lot, and put their kid in the middle, then watch out—this is the kid who will succumb.” But if the divorcing parents get along, if they provide their child with the other psychological nutrients he needs, then even an orchid child can do just fine.

Most people would appreciate the flexibility of this message, I think; few of us had problem-free childhoods.

But there’s another kind of flexibility that we all hope applies to the question of who we are and what we become. We want the freedom to map our own destinies. We want to preserve the advantageous aspects of our temperaments and improve, or even discard, the ones we dislike—such as a horror of public speaking. In addition to our inborn temperaments, beyond the luck of the draw of our childhood experience, we want to believe that we—as adults—can shape our selves and make what we will of our lives.

Can we?