Quiet

4 IS TEMPERAMENT DESTINY? Nature, Nurture, and the Orchid Hypothesis

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 feel when 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?

5 BEYOND TEMPERAMENT: The Role of Free Will (and the Secret of Public Speaking for Introverts)

Deep inside the bowels of the Athinoula A. Martinos Center for Biomedical Imaging at Massachusetts General Hospital, the hallways are nondescript, dingy even. I’m standing outside the locked door of a windowless room with Dr. Carl Schwartz, the director of the Developmental Neuroimaging and Psychopathology Research Lab. Schwartz has bright, inquisitive eyes, graying brown hair, and a quietly enthusiastic manner. Despite our unprepossessing surroundings, he prepares with some fanfare to unlock the door.

The room houses a multimillion-dollar fMRI (functional magnetic resonance imaging) machine, which has made possible some of the greatest breakthroughs in modern neuroscience. An fMRI machine can measure which parts of the brain are active when you’re thinking a particular thought or performing a specific task, allowing scientists to perform the once unimaginable task of mapping the functions of the human brain. A principal inventor of the fMRI technique, says Dr. Schwartz, was a brilliant but unassuming scientist named Kenneth Kwong, who works inside this very building. This whole place is full of quiet and modest people doing extraordinary things, Schwartz adds, waving his hand appreciatively at the empty hallway.

Before Schwartz opens the door, he asks me to take off my gold hoop earrings and set aside the metal tape recorder I’ve been using to record our conversation. The magnetic field of the fMRI machine is 100,000 times stronger than the earth’s gravitational pull—so strong, Schwartz says, that it could rip the earrings right out of my ears if they were magnetic and send them flying across the room. I worry about the metal fasteners of my bra, but I’m too embarrassed to ask. I point instead to my shoe buckle, which I figure has the same amount of metal as the bra strap. Schwartz says it’s all right, and we enter the room.

We gaze reverently at the fMRI scanner, which looks like a gleaming rocketship lying on its side. Schwartz explains that he asks his subjects—who are in their late teens—to lie down with their heads in the scanner while they look at photographs of faces and the machine tracks how their brains respond. He’s especially interested in activity in the amygdala—the same powerful organ inside the brain that Kagan found played such an important role in shaping some introverts’ and extroverts’ personalities.

Schwartz is Kagan’s colleague and protégé, and his work picks up just where Kagan’s longitudinal studies of personality left off. The infants Kagan once categorized as high- and low-reactive have now grown up, and Schwartz is using the fMRI machine to peer inside their brains. Kagan followed his subjects from infancy into adolescence, but Schwartz wanted to see what happened to them after that. Would the footprint of temperament be detectable, all those years later, in the adult brains of Kagan’s high- and low-reactive infants? Or would it have been erased by some combination of environment and conscious effort?

Interestingly, Kagan cautioned Schwartz against doing the study. In the competitive field of science research, you don’t want to waste time conducting studies that may not yield significant findings. And Kagan worried that there were no results to be found—that the link between temperament and destiny would be severed by the time an infant reached adulthood.

“He was trying to take care of me,” Schwartz tells me. “It was an interesting paradox. Because here Jerry was doing all these early observations of infants, and seeing that it wasn’t just their social behavior that was different in the extremes—everything about these kids was different. Their eyes dilated more widely when they were solving problems, their vocal cords became more tense while uttering words, their heart rate patterns were unique: there were all these channels that suggested there was something different physiologically about these kids. And I think, in spite of this, because of his intellectual heritage, he had the feeling that environmental factors are so complex that it would be really hard to pick up that footprint of temperament later in life.”

But Schwartz, who believes that he’s a high-reactive himself and was drawing partly on his own experience, had a hunch that he’d find that footprint even farther along the longitudinal timeline than Kagan had.

He demonstrates his research by allowing me to act as if I were one of his subjects, albeit not inside the fMRI scanner. As I sit at a desk, a computer monitor flashes photos at me, one after another, each showing an unfamiliar face: disembodied black-and-white heads floating against a dark background. I think I can feel my pulse quicken as the photos start coming at me faster and faster. I also notice that Schwartz has slipped in some repeats and that I feel more relaxed as the faces start to look familiar. I describe my reactions to Schwartz, who nods. The slide show is designed, he says, to mimic an environment that corresponds to the sense that high-reactive people get when they walk into a crowded room of strangers and feel “Geez! Who are these people?”

I wonder if I’m imagining my reactions, or exaggerating them, but Schwartz tells me that he’s gotten back the first set of data on a group of high-reactive children Kagan studied from four months of age—and sure enough, the amygdalae of those children, now grown up, had turned out to be more sensitive to the pictures of unfamiliar faces than did the amygdalae of those who’d been bold toddlers. Both groups reacted to the pictures, but the formerly shy kids reacted more. In other words, the footprint of a high- or low-reactive temperament never disappeared in adulthood. Some high-reactives grew into socially fluid teenagers who were not outwardly rattled by novelty, but they never shed their genetic inheritance.

Schwartz’s research suggests something important: we can stretch our personalities, but only up to a point. Our inborn temperaments influence us, regardless of the lives we lead. A sizable part of who we are is ordained by our genes, by our brains, by our nervous systems. And yet the elasticity that Schwartz found in some of the high-reactive teens also suggests the converse: we have free will and can use it to shape our personalities.

These seem like contradictory principles, but they are not. Free will can take us far, suggests Dr. Schwartz’s research, but it cannot carry us infinitely beyond our genetic limits. Bill Gates is never going to be Bill Clinton, no matter how he polishes his social skills, and Bill Clinton can never be Bill Gates, no matter how much time he spends alone with a computer.

We might call this the “rubber band theory” of personality. We are like rubber bands at rest. We are elastic and can stretch ourselves, but only so much.

To understand why this might be so for high-reactives, it helps to look at what happens in the brain when we greet a stranger at a cocktail party. Remember that the amygdala, and the limbic system of which it’s a key part, is an ancient part of the brain—so old that primitive mammals have their own versions of this system. But as mammals became more complex, an area of the brain called the neocortex developed around the limbic system. The neocortex, and particularly the frontal cortex in humans, performs an astonishing array of functions, from deciding which brand of toothpaste to buy, to planning a meeting, to pondering the nature of reality. One of these functions is to soothe unwarranted fears.

If you were a high-reactive baby, then your amygdala may, for the rest of your life, go a bit wild every time you introduce yourself to a stranger at a cocktail party. But if you feel relatively skilled in company, that’s partly because your frontal cortex is there to tell you to calm down, extend a handshake, and smile. In fact, a recent fMRI study shows that when people use self-talk to reassess upsetting situations, activity in their prefrontal cortex increases in an amount correlated with a decrease of activity in their amygdala.

But the frontal cortex isn’t all-powerful; it doesn’t switch the amygdala off altogether. In one study, scientists conditioned a rat to associate a certain sound with an electrical shock. Then they played that sound over and over again without administering the shock, until the rats lost their fear.

But it turned out that this “unlearning” was not as complete as the scientists first thought. When they severed the neural connections between the rats’ cortex and amygdala, the rats became afraid of the sound again. This was because the fear conditioning had been suppressed by the activity of the cortex, but was still present in the amygdala. In humans with unwarranted fears, like batophobia, or fear of heights, the same thing happens. Repeated trips to the top of the Empire State Building seem to extinguish the fear, but it may come roaring back during times of stress—when the cortex has other things to do than soothe an excitable amygdala.

This helps explain why many high-reactive kids retain some of the fearful aspects of their temperament all the way into adulthood, no matter how much social experience they acquire or free will they exercise. My colleague Sally is a good example of this phenomenon. Sally is a thoughtful and talented book editor, a self-described shy introvert, and one of the most charming and articulate people I know. If you invite her to a party, and later ask your other guests whom they most enjoyed meeting, chances are they’ll mention Sally. She’s so sparkly, they’ll tell you. So witty! So adorable!

Sally is conscious of how well she comes across—you can’t be as appealing as she is without being aware of it. But that doesn’t mean her amygdala knows it. When she arrives at a party, Sally often wishes she could hide behind the nearest couch—until her prefrontal cortex takes over and she remembers what a good conversationalist she is. Even so, her amygdala, with its lifetime of stored associations between strangers and anxiety, sometimes prevails. Sally admits that sometimes she drives an hour to a party and then leaves five minutes after arriving.

When I think of my own experiences in light of Schwartz’s findings, I realize it’s not true that I’m no longer shy; I’ve just learned to talk myself down from the ledge (thank you, prefrontal cortex!). By now I do it so automatically that I’m hardly aware it’s happening. When I talk with a stranger or a group of people, my smile is bright and my manner direct, but there’s a split second that feels like I’m stepping onto a high wire. By now I’ve had so many thousands of social experiences that I’ve learned that the high wire is a figment of my imagination, or that I won’t die if I fall. I reassure myself so instantaneously that I’m barely aware I’m doing it. But the reassurance process is still happening—and occasionally it doesn’t work. The word that Kagan first used to describe high-reactive people was inhibited, and that’s exactly how I still feel at some dinner parties.

This ability to stretch ourselves—within limits—applies to extroverts, too. One of my clients, Alison, is a business consultant, mother, and wife with the kind of extroverted personality—friendly, forthright, perpetually on the go—that makes people describe her as a “force of nature.” She has a happy marriage, two daughters she adores, and her own consulting firm that she built from scratch. She’s rightly proud of what she’s accomplished in life.

But she hasn’t always felt so satisfied. The year she graduated from high school, she took a good look at herself and didn’t like what she saw. Alison is extremely bright, but you couldn’t see that from her high school transcript. She’d had her heart set on attending an Ivy League school, and had thrown that chance away.

And she knew why. She’d spent high school socializing—Alison was involved in practically every extracurricular activity her school had to offer—and that didn’t leave much time for academics. Partly she blamed her parents, who were so proud of their daughter’s social gifts that they hadn’t insisted she study more. But mostly she blamed herself.

As an adult, Alison is determined not to make similar mistakes. She knows how easy it would be to lose herself in a whirl of PTA meetings and business networking. So Alison’s solution is to look to her family for adaptive strategies. She happens to be the only child of two introverted parents, to be married to an introvert, and to have a younger daughter who is a strong introvert herself.

Alison has found ways to tap into the wavelength of the quiet types around her. When she visits her parents, she finds herself meditating and writing in her journal, just the way her mother does. At home she relishes peaceful evenings with her homebody husband. And her younger daughter, who enjoys intimate backyard talks with her mother, has Alison spending her afternoons engaged in thoughtful conversation.

Alison has even created a network of quiet, reflective friends. Although her best friend in the world, Amy, is a highly charged extrovert just like her, most of her other friends are introverts. “I so appreciate people who listen well,” says Alison. “They are the friends I go have coffee with. They give me the most spot-on observations. Sometimes I haven’t even realized I was doing something counterproductive, and my introverted friends will say, ‘Here’s what you’re doing, and here are fifteen examples of when you did that same thing,’ whereas my friend Amy wouldn’t even notice. But my introverted friends are sitting back and observing, and we can really connect over that.”

Alison remains her boisterous self, but she has also discovered how to be, and to benefit from, quiet.

Even though we can reach for the outer limits of our temperaments, it can often be better to situate ourselves squarely inside our comfort zones.

Consider the story of my client Esther, a tax lawyer at a large corporate law firm. A tiny brunette with a springy step and blue eyes as bright as headlamps, Esther was not shy and never had been. But she was decidedly introverted. Her favorite part of the day was the quiet ten minutes when she walked to the bus along the tree-lined streets of her neighborhood. Her second favorite part was when she got to close the door to her office and dig into her work.

Esther had chosen her career well. A mathematician’s daughter, she loved to think about intimidatingly complex tax problems, and could discuss them with ease. (In chapter 7, I examine why introverts are so good at complex, focused problem-solving.) She was the youngest member of a close-knit working group operating inside a much larger law firm. This group comprised five other tax lawyers, all of whom supported one another’s careers. Esther’s work consisted of thinking deeply about questions that fascinated her and working closely with trusted colleagues.

But it happened that Esther’s small group of tax lawyers periodically had to give presentations to the rest of the law firm. These talks were a source of misery for Esther, not because she was afraid of public speaking, but because she wasn’t comfortable speaking extemporaneously. Esther’s colleagues, in contrast—all of whom happened to be extroverts—were spontaneous talkers who decided what they’d say on their way to the presentation and were somehow able to convey their thoughts intelligibly and engagingly by the time they arrived.

Esther was fine if given a chance to prepare, but sometimes her colleagues failed to mention that they’d be delivering a talk until she arrived at work that morning. She assumed that their ability to speak improvisationally was a function of their superior understanding of tax law and that, as she gained more experience, she too would be able to “wing it.” But as Esther became more senior and more knowledgeable, she still couldn’t do it.

To solve Esther’s problem, let’s focus on another difference between introverts and extroverts: their preference for stimulation.

For several decades, beginning in the late 1960s, an influential research psychologist named Hans Eysenck hypothesized that human beings seek “just right” levels of stimulation—not too much and not too little. Stimulation is the amount of input we have coming in from the outside world. It can take any number of forms, from noise to social life to flashing lights. Eysenck believed that extroverts prefer more stimulation than introverts do, and that this explained many of their differences: introverts enjoy shutting the doors to their offices and plunging into their work, because for them this sort of quiet intellectual activity is optimally stimulating, while extroverts function best when engaged in higher-wattage activities like organizing team-building workshops or chairing meetings.

Eysenck also thought that the basis of these differences might be found in a brain structure called the ascending reticular activating system (ARAS). The ARAS is a part of the brain stem that has connections leading up to the cerebral cortex and other parts of the brain. The brain has excitatory mechanisms that cause us to feel awake, alert, and energetic—“aroused,” in the parlance of psychologists. It also has calming mechanisms that do the opposite. Eysenck speculated that the ARAS regulates the balance between over- and under-arousal by controlling the amount of sensory stimulation that flows into the brain; sometimes the channels are wide open, so a lot of stimulation can get in, and sometimes they’re constricted, so the brain is less stimulated. Eysenck thought that the ARAS functioned differently in introverts and extroverts: introverts have wide-open information channels, causing them to be flooded with stimulation and over-aroused, while extroverts have tighter channels, making them prone to under-arousal. Over-arousal doesn’t produce anxiety so much as the sense that you can’t think straight—that you’ve had enough and would like to go home now. Under-arousal is something like cabin fever. Not enough is happening: you feel itchy, restless, and sluggish, like you need to get out of the house already.

Today we know that the reality is far more complex. For one thing, the ARAS doesn’t turn stimulation on and off like a fire truck’s hose, flooding the entire brain at once; different parts of the brain are aroused more than others at different times. Also, high arousal levels in the brain don’t always correlate with how aroused we feel. And there are many different kinds of arousal: arousal by loud music is not the same as arousal by mortar fire, which is not the same as arousal by presiding at a meeting; you might be more sensitive to one form of stimulation than to another. It’s also too simple to say that we always seek moderate levels of arousal: excited fans at a soccer game crave hyperstimulation, while people who visit spas for relaxation treatments seek low levels.

Still, more than a thousand studies conducted by scientists worldwide have tested Eysenck’s theory that cortical arousal levels are an important clue to the nature of introversion and extroversion, and it appears to be what the personality psychologist David Funder calls “half-right”—in very important ways. Whatever the underlying cause, there’s a host of evidence that introverts are more sensitive than extroverts to various kinds of stimulation, from coffee to a loud bang to the dull roar of a networking event—and that introverts and extroverts often need very different levels of stimulation to function at their best.

In one well-known experiment, dating all the way back to 1967 and still a favorite in-class demonstration in psychology courses, Eysenck placed lemon juice on the tongues of adult introverts and extroverts to find out who salivated more. Sure enough, the introverts, being more aroused by sensory stimuli, were the ones with the watery mouths.

In another famous study, introverts and extroverts were asked to play a challenging word game in which they had to learn, through trial and error, the governing principle of the game. While playing, they wore headphones that emitted random bursts of noise. They were asked to adjust the volume of their headsets up or down to the level that was “just right.” On average, the extroverts chose a noise level of 72 decibels, while the introverts selected only 55 decibels. When working at the volume that they had selected—loud for the extroverts, quiet for the introverts—the two types were about equally aroused (as measured by their heart rates and other indicators). They also played equally well.

When the introverts were asked to work at the noise level preferred by the extroverts, and vice versa, everything changed. Not only were the introverts over-aroused by the loud noise, but they also underperformed—taking an average of 9.1 trials rather than 5.8 to learn the game. The opposite was true for the extroverts—they were under-aroused (and possibly bored) by the quieter conditions, and took an average of 7.3 trials, compared with the 5.4 they’d averaged under noisier conditions.

When combined with Kagan’s findings on high reactivity, this line of studies offers a very empowering lens through which to view your personality. Once you understand introversion and extroversion as preferences for certain levels of stimulation, you can begin consciously trying to situate yourself in environments favorable to your own personality—neither overstimulating nor understimulating, neither boring nor anxiety-making. You can organize your life in terms of what personality psychologists call “optimal levels of arousal” and what I call “sweet spots,” and by doing so feel more energetic and alive than before.

Your sweet spot is the place where you’re optimally stimulated. You probably seek it out already without being aware that you’re doing so. Imagine that you’re lying contentedly in a hammock reading a great novel. This is a sweet spot. But after half an hour you realize that you’ve read the same sentence five times; now you’re understimulated. So you call a friend and go out for brunch—in other words, you ratchet up your stimulation level—and as you laugh and gossip over blueberry pancakes, you’re back, thank goodness, inside your sweet spot. But this agreeable state lasts only until your friend—an extrovert who needs much more stimulation than you do—persuades you to accompany her to a block party, where you’re now confronted by loud music and a sea of strangers.

Your friend’s neighbors seem affable enough, but you feel pressured to make small talk above the din of music. Now—bang, just like that—you’ve fallen out of your sweet spot, except this time you’re overstimulated. And you’ll probably feel that way until you pair off with someone on the periphery of the party for an in-depth conversation, or bow out altogether and return to your novel.

Imagine how much better you’ll be at this sweet-spot game once you’re aware of playing it. You can set up your work, your hobbies, and your social life so that you spend as much time inside your sweet spot as possible. People who are aware of their sweet spots have the power to leave jobs that exhaust them and start new and satisfying businesses. They can hunt for homes based on the temperaments of their family members—with cozy window seats and other nooks and crannies for the introverts, and large, open living-dining spaces for the extroverts.

Understanding your sweet spot can increase your satisfaction in every arena of your life, but it goes even further than that. Evidence suggests that sweet spots can have life-or-death consequences. According to a recent study of military personnel conducted through the Walter Reed Army Institute of Research, introverts function better than extroverts when sleep deprived, which is a cortically de-arousing condition (because losing sleep makes us less alert, active, and energetic). Drowsy extroverts behind the wheel should be especially careful—at least until they increase their arousal levels by chugging coffee or cranking up the radio. Conversely, introverts driving in loud, overly arousing traffic noise should work to stay focused, since the noise may impair their thinking.

Now that we know about optimal levels of stimulation, Esther’s problem—winging it at the podium—also makes sense. Overarousal interferes with attention and short-term memory—key components of the ability to speak on the fly. And since public speaking is an inherently stimulating activity—even for those, like Esther, who suffer no stage fright—introverts can find their attention impaired just when they need it most. Esther could live to be a one-hundred-year-old lawyer, in other words, the most knowledgeable practitioner in her field, and she might never be comfortable speaking extemporaneously. She might find herself perpetually unable, at speech time, to draw on the massive body of data sitting inside her long-term memory.

But once Esther understands herself, she can insist to her colleagues that they give her advance notice of any speaking events. She can practice her speeches and find herself well inside her sweet spot when finally she reaches the podium. She can prepare the same way for client meetings, networking events, even casual meetings with her colleagues—any situation of heightened intensity in which her short-term memory and the ability to think on her feet might be a little more compromised than usual.

Esther managed to solve her problem from the comfort of her sweet spot. Yet sometimes stretching beyond it is our only choice. Some years ago I decided that I wanted to conquer my fear of public speaking. After much hemming and hawing, I signed up for a workshop at the Public Speaking–Social Anxiety Center of New York. I had my doubts; I felt like a garden-variety shy person, and I didn’t like the pathological sound of the term “social anxiety.” But the class was based on desensitization training, an approach that made sense to me. Often used as a way to conquer phobias, desensitization involves exposing yourself (and your amygdala) to the thing you’re afraid of over and over again, in manageable doses. This is very different from the well-meaning but unhelpful advice that you should just jump in at the deep end and try to swim—an approach that might work, but more likely will produce panic, further encoding in your brain a cycle of dread, fear, and shame.

I found myself in good company. There were about fifteen people in the class, which was led by Charles di Cagno, a wiry, compact man with warm brown eyes and a sophisticated sense of humor. Charles is himself a veteran of exposure therapy. Public speaking anxiety doesn’t keep him up at night anymore, he says, but fear is a wily enemy and he’s always working to get the better of it.

The workshop had been in session for a few weeks before I joined, but Charles assured me that newcomers were welcome. The group was more diverse than I expected. There was a fashion designer with long, curly hair, bright lipstick, and pointy snakeskin boots; a secretary with thick glasses and a clipped, matter-of-fact manner, who talked a lot about her Mensa membership; a couple of investment bankers, tall and athletic; an actor with black hair and vivid blue eyes who bounded cheerfully across the room in his Puma sneakers but claimed to be terrified the entire time; a Chinese software designer with a sweet smile and a nervous laugh. A regular cross-section of New Yorkers, really. It might have been a class in digital photography or Italian cooking.

Except that it wasn’t. Charles explained that each of us would speak in front of the group, but at an anxiety level we could handle.

A martial arts instructor named Lateesha was first up that evening. Lateesha’s assignment was to read aloud to the class from a Robert Frost poem. With her dreadlocks and wide smile, Lateesha looked as if she wasn’t afraid of anything. But as she got ready to speak, her book propped open at the podium, Charles asked how anxious she was, on a scale of 1 to 10.

“At least seven,” said Lateesha.

“Take it slow,” he said. “There are only a few people out there who can completely overcome their fears, and they all live in Tibet.”

Lateesha read the poem clearly and quietly, with only the slightest tremor in her voice. When she was finished, Charles beamed proudly.

“Stand up please, Lisa,” he said, addressing an attractive young marketing director with shiny black hair and a gleaming engagement ring. “It’s your turn to offer feedback. Did Lateesha look nervous?”

“No,” said Lisa.

“I was really scared, though,” Lateesha said.

“Don’t worry, no one could tell,” Lisa assured her.

The others nodded their heads vigorously. Couldn’t tell at all, they echoed. Lateesha sat down, looking pleased.

Next it was my turn. I stood at a makeshift podium—really a music stand—and faced the group. The only sound in the room was the ticking of the ceiling fan and the blare of traffic outside. Charles asked me to introduce myself. I took a deep breath.

“HELLOOO!!!!” I shouted, hoping to sound dynamic.

Charles looked alarmed. “Just be yourself,” he said.

My first exercise was simple. All I had to do was answer a few questions that people called out: Where do you live? What do you do for a living? What did you do this weekend?

I answered the questions in my normal, soft-spoken way. The group listened carefully.

“Does anyone have any more questions for Susan?” asked Charles. The group shook their heads.

“Now, Dan,” said Charles, nodding at a strapping red-haired fellow who looked like one of those CNBC journalists reporting directly from the New York Stock Exchange, “you’re a banker and you have tough standards. Tell me, did Susan look nervous?”

“Not at all,” said Dan.

The rest of the group nodded. Not nervous at all, they murmured—just as they had for Lateesha.

You seem so outgoing, they added.

You came across as really confident!

You’re lucky because you never run out of things to say.

I sat down feeling pretty good about myself. But soon I saw that Lateesha and I weren’t the only ones to get that kind of feedback. A few others did as well. “You looked so calm!” these speakers were told, to their visible relief. “No one would ever know if they didn’t know! What are you doing in this class?”

At first I wondered why I prized these reassurances so highly. Then I realized that I was attending the workshop because I wanted to stretch myself to the outer limits of my temperament. I wanted to be the best and bravest speaker I could be. The reassurances were evidence that I was on my way toward achieving this goal. I suspected that the feedback I was getting was overly charitable, but I didn’t care. What mattered was that I’d addressed an audience that had received me well, and I felt good about the experience. I had begun to desensitize myself to the horrors of public speaking.

Since then, I’ve done plenty of speaking, to groups of ten and crowds of hundreds. I’ve come to embrace the power of the podium. For me this involves taking specific steps, including treating every speech as a creative project, so that when I get ready for the big day, I experience that delving-deep sensation I enjoy so much. I also speak on topics that matter to me deeply, and have found that I feel much more centered when I truly care about my subject.

This isn’t always possible, of course. Sometimes speakers need to talk about subjects that don’t interest them much, especially at work. I believe this is harder for introverts, who have trouble projecting artificial enthusiasm. But there’s a hidden advantage to this inflexibility: it can motivate us to make tough but worthwhile career changes if we find ourselves compelled to speak too often about topics that leave us cold. There is no one more courageous than the person who speaks with the courage of his convictions.

6 “FRANKLIN WAS A POLITICIAN, BUT ELEANOR SPOKE OUT OF CONSCIENCE” Why Cool Is Overrated

Easter Sunday, 1939. The Lincoln Memorial. Marian Anderson, one of the most extraordinary singers of her generation, takes the stage, the statue of the sixteenth president rising up behind her. A regal woman with toffee-colored skin, she gazes at her audience of 75,000: men in brimmed hats, ladies in their Sunday best, a great sea of black and white faces. “My country ’tis of thee,” she begins, her voice soaring, each word pure and distinct. “Sweet land of liberty.” The crowd is rapt and tearful. They never thought this day would come to pass.

And it wouldn’t have, without Eleanor Roosevelt. Earlier that year, Anderson had planned to sing at Constitution Hall in Washington, D.C., but the Daughters of the American Revolution, who owned the hall, rejected her because of her race. Eleanor Roosevelt, whose family had fought in the Revolution, resigned from the DAR, helped arrange for Anderson to sing at the Lincoln Memorial—and ignited a national firestorm. Roosevelt was not the only one to protest, but she brought political clout to the issue, risking her own reputation in the process.

For Roosevelt, who seemed constitutionally unable to look away from other people’s troubles, such acts of social conscience were nothing unusual. But others appreciated how remarkable they were. “This was something unique,” recalled the African-American civil rights leader James Farmer of Roosevelt’s brave stand. “Franklin was a politician. He weighed the political consequences of every step that he took. He was a good politician, too. But Eleanor spoke out of conscience, and acted as a conscientious person. That was different.”

It was a role she played throughout their life together: Franklin’s adviser, Franklin’s conscience. He may have chosen her for just this reason; in other ways they were such an unlikely pair.

They met when he was twenty. Franklin was her distant cousin, a sheltered Harvard senior from an upper-crust family. Eleanor was only nineteen, also from a moneyed clan, but she had chosen to immerse herself in the sufferings of the poor, despite her family’s disapproval. As a volunteer at a settlement house on Manhattan’s impoverished Lower East Side, she had met children who were forced to sew artificial flowers in windowless factories to the point of exhaustion. She took Franklin with her one day. He couldn’t believe that human beings lived in such miserable conditions—or that a young woman of his own class had been the one to open his eyes to this side of America. He promptly fell in love with her.

But Eleanor wasn’t the light, witty type he’d been expected to marry. Just the opposite: she was slow to laugh, bored by small talk, serious-minded, shy. Her mother, a fine-boned, vivacious aristocrat, had nicknamed her “Granny” because of her demeanor. Her father, the charming and popular younger brother of Theodore Roosevelt, doted on her when he saw her, but he was drunk most of the time, and died when Eleanor was nine. By the time Eleanor met Franklin, she couldn’t believe that someone like him would be interested in her. Franklin was everything that she was not: bold and buoyant, with a wide, irrepressible grin, as easy with people as she was cautious. “He was young and gay and good looking,” Eleanor recalled, “and I was shy and awkward and thrilled when he asked me to dance.”

At the same time, many told Eleanor that Franklin wasn’t good enough for her. Some saw him as a lightweight, a mediocre scholar, a frivolous man-about-town. And however poor Eleanor’s own self-image, she did not lack for admirers who appreciated her gravitas. Some of her suitors wrote grudging letters of congratulations to Franklin when he won her hand. “I have more respect and admiration for Eleanor than any girl I have ever met,” one letter-writer said. “You are mighty lucky. Your future wife is such as it is the privilege of few men to have,” said another.

But public opinion was beside the point for Franklin and Eleanor. Each had strengths that the other craved—her empathy, his bravado. “E is an Angel,” Franklin wrote in his journal. When she accepted his marriage proposal in 1903, he proclaimed himself the happiest man alive. She responded with a flood of love letters. They were married in 1905 and went on to have six children.

Despite the excitement of their courtship, their differences caused trouble from the start. Eleanor craved intimacy and weighty conversations; he loved parties, flirting, and gossip. The man who would declare that he had nothing to fear but fear itself could not understand his wife’s struggles with shyness. When Franklin was appointed assistant secretary of the navy in 1913, the pace of his social life grew ever more frenzied and the settings more gilded—elite private clubs, his Harvard friends’ mansions. He caroused later and later into the night. Eleanor went home earlier and earlier.

In the meantime, Eleanor found herself with a full calendar of social duties. She was expected to pay visits to the wives of other Washington luminaries, leaving calling cards at their doors and holding open houses in her own home. She didn’t relish this role, so she hired a social secretary named Lucy Mercer to help her. Which seemed a good idea—until the summer of 1917, when Eleanor took the children to Maine for the summer, leaving Franklin behind in Washington with Mercer. The two began a lifelong affair. Lucy was just the kind of lively beauty Franklin had been expected to marry in the first place.

Eleanor found out about Franklin’s betrayal when she stumbled on a packet of love letters in his suitcase. She was devastated, but stayed in the marriage. And although they never rekindled the romantic side of their relationship, she and Franklin replaced it with something formidable: a union of his confidence with her conscience.

Fast-forward to our own time, where we’ll meet another woman of similar temperament, acting out of her own sense of conscience. Dr. Elaine Aron is a research psychologist who, since her first scientific publication in 1997, has singlehandedly reframed what Jerome Kagan and others call high reactivity (and sometimes “negativity” or “inhibition”). She calls it “sensitivity,” and along with her new name for the trait, she’s transformed and deepened our understanding of it.

When I hear that Aron will be the keynote speaker at an annual weekend gathering of “highly sensitive people” at Walker Creek Ranch in Marin County, California, I quickly buy plane tickets. Jacquelyn Strickland, a psychotherapist and the founder and host of the event, explains that she created these weekends so that sensitive people could benefit from being in one another’s presence. She sends me an agenda explaining that we’ll be sleeping in rooms designated for “napping, journaling, puttering, meditating, organizing, writing, and reflecting.”

“Please do socialize very quietly in your room (with consent of your roommate), or preferably in the group areas on walks and at mealtimes,” says the agenda. The conference is geared to people who enjoy meaningful discussions and sometimes “move a conversation to a deeper level, only to find out we are the only ones there.” There will be plenty of time for serious talk this weekend, we’re assured. But we’ll also be free to come and go as we please. Strickland knows that most of us will have weathered a lifetime of mandatory group activities, and she wants to show us a different model, if only for a few days.

Walker Creek Ranch sits on 1,741 acres of unspoiled Northern California wilderness. It offers hiking trails and wildlife and vast crystalline skies, but at its center is a cozy, barnlike conference center where about thirty of us gather on a Thursday afternoon in the middle of June. The Buckeye Lodge is outfitted with grey industrial carpets, large whiteboards, and picture windows overlooking sunny redwood forests. Alongside the usual piles of registration forms and name badges, there’s a flip chart where we’re asked to write our name and Myers-Briggs personality type. I scan the list. Everyone’s an introvert except for Strickland, who is warm, welcoming, and expressive. (According to Aron’s research, the majority, though not all, of sensitive people are introverts.)

The tables and chairs in the room are organized in a big square so that we can all sit and face one another. Strickland invites us—participation optional—to share what brought us here. A software engineer named Tom kicks off, describing with great passion his relief at learning that there was “a physiological basis for the trait of sensitivity. Here’s the research! This is how I am! I don’t have to try to meet anyone’s expectations anymore. I don’t need to feel apologetic or defensive in any way.” With his long, narrow face, brown hair, and matching beard, Tom reminds me of Abraham Lincoln. He introduces his wife, who talks about how compatible she and Tom are, and how together they stumbled across Aron’s work.

When it’s my turn, I talk about how I’ve never been in a group environment in which I didn’t feel obliged to present an unnaturally rah-rah version of myself. I say that I’m interested in the connection between introversion and sensitivity. Many people nod.

On Saturday morning, Dr. Aron appears in the Buckeye Lodge. She waits playfully behind an easel containing a flip chart while Strickland introduces her to the audience. Then she emerges smiling—ta-da!—from behind the easel, sensibly clad in a blazer, turtleneck, and corduroy skirt. She has short, feathery brown hair and warm, crinkly blue eyes that look as if they don’t miss a thing. You can see immediately the dignified scholar Aron is today, as well as the awkward schoolgirl she must once have been. You can see, too, her respect for her audience.

Getting right down to business, she informs us that she has five different subtopics she can discuss, and asks us to raise our hands to vote for our first, second, and third choice of subjects. Then she performs, rapid-fire, an elaborate mathematical calculation from which she determines the three subtopics for which we’ve collectively voted. The crowd settles down amiably. It doesn’t really matter which subtopics we’ve chosen; we know that Aron is here to talk about sensitivity, and that she’s taking our preferences into consideration.

Some psychologists make their mark by doing unusual research experiments. Aron’s contribution is to think differently, radically differently, about studies that others have done. When she was a girl, Aron was often told that she was “too sensitive for her own good.” She had two hardy elder siblings and was the only child in her family who liked to daydream, and play inside, and whose feelings were easily hurt. As she grew older and ventured outside her family’s orbit, she continued to notice things about herself that seemed different from the norm. She could drive alone for hours and never turn on the radio. She had strong, sometimes disturbing dreams at night. She was “strangely intense,” and often beset by powerful emotions, both positive and negative. She had trouble finding the sacred in the everyday; it seemed to be there only when she withdrew from the world.

Aron grew up, became a psychologist, and married a robust man who loved these qualities. To her husband, Art, Aron was creative, intuitive, and a deep thinker. She appreciated these things in herself, too, but saw them as “acceptable surface manifestations of a terrible, hidden flaw I had been aware of all my life.” She thought it was a miracle that Art loved her in spite of this flaw.

But when one of her fellow psychologists casually described Aron as “highly sensitive,” a lightbulb went on in her head. It was as if these two words described her mysterious failing, except that the psychologist hadn’t been referring to a flaw at all. It had been a neutral description.

Aron pondered this new insight, and then set out to research this trait called “sensitivity.” She came up mostly dry, so she pored over the vast literature on introversion, which seemed to be intimately related: Kagan’s work on high-reactive children, and the long line of experiments on the tendency of introverts to be more sensitive to social and sensory stimulation. These studies gave her glimpses of what she was looking for, but Aron thought that there was a missing piece in the emerging portrait of introverted people.

“The problem for scientists is that we try to observe behavior, and these are things that you cannot observe,” she explains. Scientists can easily report on the behavior of extroverts, who can often be found laughing, talking, or gesticulating. But “if a person is standing in the corner of a room, you can attribute about fifteen motivations to that person. But you don’t really know what’s going on inside.”

Yet inner behavior was still behavior, thought Aron, even if it was difficult to catalog. So what is the inner behavior of people whose most visible feature is that when you take them to a party they aren’t very pleased about it? She decided to find out.

First Aron interviewed thirty-nine people who described themselves as being either introverted or easily overwhelmed by stimulation. She asked them about the movies they liked, their first memories, relationships with parents, friendships, love lives, creative activities, philosophical and religious views. Based on these interviews, she created a voluminous questionnaire that she gave to several large groups of people. Then she boiled their responses down to a constellation of twenty-seven attributes. She named the people who embodied these attributes “highly sensitive.”

Some of these twenty-seven attributes were familiar from Kagan and others’ work. For example, highly sensitive people tend to be keen observers who look before they leap. They arrange their lives in ways that limit surprises. They’re often sensitive to sights, sounds, smells, pain, coffee. They have difficulty when being observed (at work, say, or performing at a music recital) or judged for general worthiness (dating, job interviews).

But there were also new insights. The highly sensitive tend to be philosophical or spiritual in their orientation, rather than materialistic or hedonistic. They dislike small talk. They often describe themselves as creative or intuitive (just as Aron’s husband had described her). They dream vividly, and can often recall their dreams the next day. They love music, nature, art, physical beauty. They feel exceptionally strong emotions—sometimes acute bouts of joy, but also sorrow, melancholy, and fear.

Highly sensitive people also process information about their environments—both physical and emotional—unusually deeply. They tend to notice subtleties that others miss—another person’s shift in mood, say, or a lightbulb burning a touch too brightly.

Recently a group of scientists at Stony Brook University tested this finding by showing two pairs of photos (of a fence and some bales of hay) to eighteen people lying inside fMRI machines. In one pair the photos were noticeably different from each other, and in the other pair the difference was much more subtle. For each pair, the scientists asked whether the second photo was the same as the first. They found that sensitive people spent more time than others looking at the photos with the subtle differences. Their brains also showed more activity in regions that help to make associations between those images and other stored information. In other words, the sensitive people were processing the photos at a more elaborate level than their peers, reflecting more on those fenceposts and haystacks.

This study is very new, and its conclusions still need to be replicated and explored in other contexts. But it echoes Jerome Kagan’s findings that high-reactive first graders spend more time than other children comparing choices when they play matching games or reading unfamiliar words. And it suggests, says Jadzia Jagiellowicz, the lead scientist at Stony Brook, that sensitive types think in an unusually complex fashion. It may also help explain why they’re so bored by small talk. “If you’re thinking in more complicated ways,” she told me, “then talking about the weather or where you went for the holidays is not quite as interesting as talking about values or morality.”

The other thing Aron found about sensitive people is that sometimes they’re highly empathic. It’s as if they have thinner boundaries separating them from other people’s emotions and from the tragedies and cruelties of the world. They tend to have unusually strong consciences. They avoid violent movies and TV shows; they’re acutely aware of the consequences of a lapse in their own behavior. In social settings they often focus on subjects like personal problems, which others consider “too heavy.”

Aron realized that she was on to something big. Many of the characteristics of sensitive people that she’d identified—such as empathy and responsiveness to beauty—were believed by psychologists to be characteristic of other personality traits like “agreeableness” and “openness to experience.” But Aron saw that they were also a fundamental part of sensitivity. Her findings implicitly challenged accepted tenets of personality psychology.

She started publishing her results in academic journals and books, and speaking publicly about her work. At first this was difficult. Audience members told her that her ideas were fascinating, but that her uncertain delivery was distracting. But Aron had a great desire to get her message out. She persevered, and learned to speak like the authority she was. By the time I saw her at Walker Creek Ranch, she was practiced, crisp, and sure. The only difference between her and your typical speaker was how conscientious she seemed about answering every last audience question. She lingered afterward with the group, even though, as an extreme introvert, she must have been itching to get home.

Aron’s description of highly sensitive people sounds as if she’s talking about Eleanor Roosevelt herself. Indeed, in the years since Aron first published her findings, scientists have found that when you put people whose genetic profiles have been tentatively associated with sensitivity and introversion (people with the gene variant of 5-HTTLPR that characterized the rhesus monkeys of chapter 3) inside an fMRI machine and show them pictures of scared faces, accident victims, mutilated bodies, and polluted scenery, the amygdala—the part of the brain that plays such an important role in processing emotions—becomes strongly activated. Aron and a team of scientists have also found that when sensitive people see faces of people experiencing strong feelings, they have more activation than others do in areas of the brain associated with empathy and with trying to control strong emotions.

It’s as if, like Eleanor Roosevelt, they can’t help but feel what others feel.

In 1921, FDR contracted polio. It was a terrible blow, and he considered retiring to the country to live out his life as an invalid gentleman. But Eleanor kept his contacts with the Democratic Party alive while he recovered, even agreeing to address a party fund-raiser. She was terrified of public speaking, and not much good at it—she had a high-pitched voice and laughed nervously at all the wrong times. But she trained for the event and made her way through the speech.

After that, Eleanor was still unsure of herself, but she began working to fix the social problems she saw all around her. She became a champion of women’s issues and forged alliances with other serious-minded people. By 1928, when FDR was elected governor of New York, she was the director of the Bureau of Women’s Activities for the Democratic Party and one of the most influential women in American politics. She and Franklin were now a fully functioning partnership of his savoir faire and her social conscience. “I knew about social conditions, perhaps more than he did,” Eleanor recalled with characteristic modesty. “But he knew about government and how you could use government to improve things. And I think we began to get an understanding of teamwork.”

FDR was elected president in 1933. It was the height of the Depression, and Eleanor traveled the country—in a single three-month period she covered 40,000 miles—listening to ordinary people tell their hard-luck stories. People opened up to her in ways they didn’t for other powerful figures. She became for Franklin the voice of the dispossessed. When she returned home from her trips, she often told him what she’d seen and pressed him to act. She helped orchestrate government programs for half-starved miners in Appalachia. She urged FDR to include women and African-Americans in his programs to put people back to work. And she helped arrange for Marian Anderson to sing at the Lincoln Memorial. “She kept at him on issues which he might, in the rush of things, have wanted to overlook,” the historian Geoff Ward has said. “She kept him to a high standard. Anyone who ever saw her lock eyes with him and say, ‘Now Franklin, you should …’ never forgot it.”

The shy young woman who’d been terrified of public speaking grew to love public life. Eleanor Roosevelt became the first First Lady to hold a press conference, address a national convention, write a newspaper column, and appear on talk radio. Later in her career she served as a U.S. delegate to the United Nations, where she used her unusual brand of political skills and hard-won toughness to help win passage of the Universal Declaration of Human Rights.

She never did outgrow her vulnerability; all her life she suffered dark “Griselda moods,” as she called them (named for a princess in a medieval legend who withdrew into silence), and struggled to “develop skin as tough as rhinoceros hide.” “I think people who are shy remain shy always, but they learn how to overcome it,” she said. But it was perhaps this sensitivity that made it easy for her to relate to the disenfranchised, and conscientious enough to act on their behalf. FDR, elected at the start of the Depression, is remembered for his compassion. But it was Eleanor who made sure he knew how suffering Americans felt.

The connection between sensitivity and conscience has long been observed. Imagine the following experiment, performed by the developmental psychologist Grazyna Kochanska. A kind woman hands a toy to a toddler, explaining that the child should be very careful because it’s one of the woman’s favorites. The child solemnly nods assent and begins to play with the toy. Soon afterward, it breaks dramatically in two, having been rigged to do so.

The woman looks upset and cries, “Oh my!” Then she waits to see what the child does next.

Some children, it turns out, feel a lot more guilty about their (supposed) transgression than others. They look away, hug themselves, stammer out confessions, hide their faces. And it’s the kids we might call the most sensitive, the most high-reactive, the ones who are likely to be introverts who feel the guiltiest. Being unusually sensitive to all experience, both positive and negative, they seem to feel both the sorrow of the woman whose toy is broken and the anxiety of having done something bad. (In case you’re wondering, the woman in the experiments quickly returned to the room with the toy “fixed” and reassurances that the child had done nothing wrong.)

In our culture, guilt is a tainted word, but it’s probably one of the building blocks of conscience. The anxiety these highly sensitive toddlers feel upon apparently breaking the toy gives them the motivation to avoid harming someone’s plaything the next time. By age four, according to Kochanska, these same kids are less likely than their peers to cheat or break rules, even when they think they can’t be caught. And by six or seven, they’re more likely to be described by their parents as having high levels of moral traits such as empathy. They also have fewer behavioral problems in general.

“Functional, moderate guilt,” writes Kochanska, “may promote future altruism, personal responsibility, adaptive behavior in school, and harmonious, competent, and prosocial relationships with parents, teachers, and friends.” This is an especially important set of attributes at a time when a 2010 University of Michigan study shows that college students today are 40 percent less empathetic than they were thirty years ago, with much of the drop having occurred since 2000. (The study’s authors speculate that the decline in empathy is related to the prevalence of social media, reality TV, and “hyper-competitiveness.”)

Of course, having these traits doesn’t mean that sensitive children are angels. They have selfish streaks like everyone else. Sometimes they act aloof and unfriendly. And when they’re overwhelmed by negative emotions like shame or anxiety, says Aron, they can be positively oblivious of other people’s needs.

But the same receptivity to experience that can make life difficult for the highly sensitive also builds their consciences. Aron tells of one sensitive teen who persuaded his mother to feed a homeless person he’d met in the park, and of another eight-year-old who cried not only when she felt embarrassed, but also when her peers were teased.

We know this type of person well from literature, probably because so many writers are sensitive introverts themselves. He “had gone through life with one skin fewer than most men,” the novelist Eric Malpass writes of his quiet and cerebral protagonist, also an author, in the novel The Long Long Dances. “The troubles of others moved him more, as did also the teeming beauty of life: moved him, compelled him, to seize a pen and write about them. [He was moved by] walking in the hills, listening to a Schubert impromptu, watching nightly from his armchair the smashing of bone and flesh that made up so much of the nine o’clock news.”

The description of such characters as thin-skinned is meant metaphorically, but it turns out that it’s actually quite literal. Among the tests researchers use to measure personality traits are skin conductance tests, which record how much people sweat in response to noises, strong emotions, and other stimuli. High-reactive introverts sweat more; low-reactive extroverts sweat less. Their skin is literally “thicker,” more impervious to stimuli, cooler to the touch. In fact, according to some of the scientists I spoke to, this is where our notion of being socially “cool” comes from; the lower-reactive you are, the cooler your skin, the cooler you are. (Incidentally, sociopaths lie at the extreme end of this coolness barometer, with extremely low levels of arousal, skin conductance, and anxiety. There is some evidence that sociopaths have damaged amygdalae.)

Lie detectors (polygraphs) are partially skin conductance tests. They operate on the theory that lying causes anxiety, which triggers the skin to perspire imperceptibly. When I was in college, I applied for a summer job as a secretary at a large jewelry company. I had to take a lie detector test as part of the application process. The test was administered in a small, dingily lit room with linoleum floors, by a thin, cigarette-puffing man with pocked yellow skin. The man asked me a series of warm-up questions: my name, address, and so on, to establish my baseline level of skin conductance. Then the questions grew more probing and the examiner’s manner harsher. Had I been arrested? Had I ever shoplifted? Had I used cocaine? With this last question my interrogator peered at me intently. As it happens, I never had tried cocaine. But he seemed to think I had. The accusing look on his face was the equivalent of the old policeman’s trick where they tell the suspect that they have the damning evidence and there’s no point denying it.

I knew the man was mistaken, but I still felt myself blush. And sure enough, the test came back showing I’d lied on the cocaine question. My skin is so thin, apparently, that it sweats in response to imaginary crimes!

We tend to think of coolness as a pose that you strike with a pair of sunglasses, a nonchalant attitude, and drink in hand. But maybe we didn’t choose these social accessories at random. Maybe we’ve adopted dark glasses, relaxed body language, and alcohol as signifiers precisely because they camouflage signs of a nervous system on overdrive. Sunglasses prevent others from seeing our eyes dilate with surprise or fear; we know from Kagan’s work that a relaxed torso is a hallmark of low reactivity; and alcohol removes our inhibitions and lowers our arousal levels. When you go to a football game and someone offers you a beer, says the personality psychologist Brian Little, “they’re really saying hi, have a glass of extroversion.”

Teenagers understand instinctively the physiology of cool. In Curtis Sittenfeld’s novel Prep, which explores the adolescent social rituals of boarding-school life with uncanny precision, the protagonist, Lee, is invited unexpectedly to the dorm room of Aspeth, the coolest girl in school. The first thing she notices is how physically stimulating Aspeth’s world is. “From outside the door, I could hear pounding music,” she observes. “White Christmas lights, currently turned on, were taped high up along all the walls, and on the north wall they’d hung an enormous orange and green tapestry.… I felt overstimulated and vaguely irritated. The room I shared with [my roommate] seemed so quiet and plain, our lives seemed so quiet and plain. Had Aspeth been born cool, I wondered, or had someone taught her, like an older sister or a cousin?”

Jock cultures sense the low-reactive physiology of cool, too. For the early U.S. astronauts, having a low heart rate, which is associated with low reactivity, was a status symbol. Lieutenant Colonel John Glenn, who became the first American to orbit the Earth and would later run for president, was admired by his comrades for his supercool pulse rate during liftoff (only 110 beats per minute).

But physical lack of cool may be more socially valuable than we think. That deep blush when a hard-bitten tester puts his face an inch from yours and asks if you’ve ever used cocaine turns out to be a kind of social glue. In a recent experiment, a team of psychologists led by Corine Dijk asked sixty-odd participants to read accounts of people who’d done something morally wrong, like driving away from a car crash, or something embarrassing, like spilling coffee on someone. The participants were shown photographs of the wrongdoers, who had one of four different facial expressions: shame or embarrassment (head and eyes down); shame/embarrassment plus a blush; neutral; or neutral with a blush. Then they were asked to rate how sympathetic and trustworthy the transgressors were.

It turned out that the offenders who blushed were judged a lot more positively than those who didn’t. This was because the blush signified concern for others. As Dacher Keltner, a psychologist at the University of California, Berkeley, who specializes in positive emotions, put it to the New York Times, “A blush comes online in two or three seconds and says, ‘I care; I know I violated the social contract.’ ”

In fact, the very thing that many high-reactives hate most about blushing—its uncontrollability—is what makes it so socially useful. “Because it is impossible to control the blush intentionally,” Dijk speculates, blushing is an authentic sign of embarrassment. And embarrassment, according to Keltner, is a moral emotion. It shows humility, modesty, and a desire to avoid aggression and make peace. It’s not about isolating the person who feels ashamed (which is how it sometimes feels to easy blushers), but about bringing people together.

Keltner has tracked the roots of human embarrassment and found that after many primates fight, they try to make up. They do this partly by making gestures of embarrassment of the kind we see in humans—looking away, which acknowledges wrongdoing and the intention to stop; lowering the head, which shrinks one’s size; and pressing the lips together, a sign of inhibition. These gestures in humans have been called “acts of devotion,” writes Keltner. Indeed, Keltner, who is trained in reading people’s faces, has studied photos of moral heroes like Gandhi and the Dalai Lama and found that they feature just such controlled smiles and averted eyes.

In his book, Born to Be Good, Keltner even says that if he had to choose his mate by asking a single question at a speed-dating event, the question he would choose is: “What was your last embarrassing experience?” Then he would watch very carefully for lip-presses, blushing, and averted eyes. “The elements of the embarrassment are fleeting statements the individual makes about his or her respect for the judgment of others,” he writes. “Embarrassment reveals how much the individual cares about the rules that bind us to one another.”

In other words, you want to make sure that your spouse cares what other people think. It’s better to mind too much than to mind too little.

No matter how great the benefits of blushing, the phenomenon of high sensitivity raises an obvious question. How did the highly sensitive manage to survive the harsh sorting-out process of evolution? If the bold and aggressive generally prevail (as it sometimes seems), why were the sensitive not selected out of the human population thousands of years ago, like tree frogs colored orange? For you may, like the protagonist of The Long Long Dances, be moved more deeply than the next person by the opening chords of a Schubert impromptu, and you may flinch more than others at the smashing of bone and flesh, and you may have been the sort of child who squirmed horribly when you thought you’d broken someone’s toy, but evolution doesn’t reward such things.

Or does it?

Elaine Aron has an idea about this. She believes that high sensitivity was not itself selected for, but rather the careful, reflective style that tends to accompany it. “The type that is ‘sensitive’ or ‘reactive’ would reflect a strategy of observing carefully before acting,” she writes, “thus avoiding dangers, failures, and wasted energy, which would require a nervous system specially designed to observe and detect subtle differences. It is a strategy of ‘betting on a sure thing’ or ‘looking before you leap.’ In contrast, the active strategy of the [other type] is to be first, without complete information and with the attendant risks—the strategy of ‘taking a long shot’ because the ‘early bird catches the worm’ and ‘opportunity only knocks once.’ ”

In truth, many people Aron considers sensitive have some of the twenty-seven attributes associated with the trait, but not all of them. Maybe they’re sensitive to light and noise, but not to coffee or pain; maybe they’re not sensitive to anything sensory, but they’re deep thinkers with a rich inner life. Maybe they’re not even introverts—only 70 percent of sensitive people are, according to Aron, while the other 30 percent are extroverts (although this group tends to report craving more downtime and solitude than your typical extrovert). This, speculates Aron, is because sensitivity arose as a by-product of survival strategy, and you need only some, not all, of the traits to pull off the strategy effectively.

There’s a great deal of evidence for Aron’s point of view. Evolutionary biologists once believed that every animal species evolved to fit an ecological niche, that there was one ideal set of behaviors for that niche, and that species members whose behavior deviated from that ideal would die off. But it turns out that it’s not only humans that divide into those who “watch and wait” and others who “just do it.” More than a hundred species in the animal kingdom are organized in roughly this way.

From fruit flies to house cats to mountain goats, from sunfish to bushbaby primates to Eurasian tit birds, scientists have discovered that approximately 20 percent of the members of many species are “slow to warm up,” while the other 80 percent are “fast” types who venture forth boldly without noticing much of what’s going on around them. (Intriguingly, the percentage of infants in Kagan’s lab who were born high-reactive was also, you’ll recall, about twenty.)

If “fast” and “slow” animals had parties, writes the evolutionary biologist David Sloan Wilson, “some of the fasts would bore everyone with their loud conversation, while others would mutter into their beer that they don’t get any respect. Slow animals are best described as shy, sensitive types. They don’t assert themselves, but they are observant and notice things that are invisible to the bullies. They are the writers and artists at the party who have interesting conversations out of earshot of the bullies. They are the inventors who figure out new ways to behave, while the bullies steal their patents by copying their behavior.”

Once in a while, a newspaper or TV program runs a story about animal personalities, casting shy behavior as unseemly and bold behavior as attractive and admirable. (That’s our kind of fruit fly!) But Wilson, like Aron, believes that both types of animals exist because they have radically different survival strategies, each of which pays off differently and at different times. This is what’s known as the trade-off theory of evolution, in which a particular trait is neither all good nor all bad, but a mix of pros and cons whose survival value varies according to circumstance.

“Shy” animals forage less often and widely for food, conserving energy, sticking to the sidelines, and surviving when predators come calling. Bolder animals sally forth, swallowed regularly by those farther up the food chain but surviving when food is scarce and they need to assume more risk. When Wilson dropped metal traps into a pond full of pumpkinseed fish, an event he says must have seemed to the fish as unsettling as a flying saucer landing on Earth, the bold fish couldn’t help but investigate—and rushed headlong into Wilson’s traps. The shy fish hovered judiciously at the edge of the pond, making it impossible for Wilson to catch them.

On the other hand, after Wilson succeeded in trapping both types of fish with an elaborate netting system and carrying them back to his lab, the bold fish acclimated quickly to their new environment and started eating a full five days earlier than did their shy brethren. “There is no single best … [animal] personality,” writes Wilson, “but rather a diversity of personalities maintained by natural selection.”

Another example of the trade-off theory of evolution is a species known as Trinidadian guppies. These guppies develop personalities—with astonishing speed, in evolutionary terms—to suit the microclimates in which they live. Their natural predators are pike. But some guppy neighborhoods, upstream of a waterfall for example, are pike-free. If you’re a guppy who grew up in such a charmed locale, then chances are you have a bold and carefree personality well suited to la dolce vita. In contrast, if your guppy family came from a “bad neighborhood” downstream from the waterfall, where pike cruise the waterways menacingly, then you probably have a much more circumspect style, just right for avoiding the bad guys.

The interesting thing is that these differences are heritable, not learned, so that the offspring of bold guppies who move into bad neighborhoods inherit their parents’ boldness—even though this puts them at a severe disadvantage compared to their vigilant peers. It doesn’t take long for their genes to mutate, though, and descendants who manage to survive tend to be careful types. The same thing happens to vigilant guppies when the pike suddenly disappear; it takes about twenty years for their descendants to evolve into fish who act as if they haven’t a care in the world.

The trade-off theory seems to apply equally to humans. Scientists have found that nomads who inherited the form of a particular gene linked to extroversion (specifically, to novelty-seeking) are better nourished than those without this version of the gene. But in settled populations, people with this same gene form have poorer nutrition. The same traits that make a nomad fierce enough to hunt and to defend livestock against raiders may hinder more sedentary activities like farming, selling goods at the market, or focusing at school.

Or consider this trade-off: human extroverts have more sex partners than introverts do—a boon to any species wanting to reproduce itself—but they commit more adultery and divorce more frequently, which is not a good thing for the children of all those couplings. Extroverts exercise more, but introverts suffer fewer accidents and traumatic injuries. Extroverts enjoy wider networks of social support, but commit more crimes. As Jung speculated almost a century ago about the two types, “the one [extroversion] consists in a high rate of fertility, with low powers of defense and short duration of life for the single individual; the other [introversion] consists in equipping the individual with numerous means of self-preservation plus a low fertility rate.”

The trade-off theory may even apply to entire species. Among evolutionary biologists, who tend to subscribe to the vision of lone individuals hell-bent on reproducing their own DNA, the idea that species include individuals whose traits promote group survival is hotly debated and, not long ago, could practically get you kicked out of the academy. But this view is slowly gaining acceptance. Some scientists even speculate that the evolutionary basis for traits like sensitivity is heightened compassion for the suffering of other members of one’s species, especially one’s family.

But you don’t have to go that far. As Aron explains, it makes sense that animal groups depend on their sensitive members for survival. “Suppose a herd of antelope … has a few members who are constantly stopping their grazing to use their keen senses to watch for predators,” she writes. “Herds with such sensitive, watchful individuals would survive better, and so continue to breed, and so continue to have some sensitive individuals born in the group.”

And why should it be any different for humans? We need our Eleanor Roosevelts as surely as grazing herds depend on their sensitive antelopes.

In addition to “shy” and “bold” animals, and to “fast” and “slow” ones, biologists sometimes speak of the “hawk” and “dove” members of a given species. Great tit birds, for example, some of whom are much more aggressive than others, often act like case studies in an international relations class. These birds feed on beech tree nuts, and in years when nuts are scarce, the hawkish female birds do better, just as you’d expect, because they’re quick to challenge nut-eating competitors to a duel. But in seasons when there are plenty of beech nuts to go around, the female “doves”—who, incidentally, tend to make more attentive mothers—do better than the “hawks,” because the hawks waste time and bodily health getting into fights for no good reason.

Male great tits, on the other hand, have the opposite pattern. This is because their main role in life is not to find food but to defend territory. In years when food is scarce, so many of their fellow tit birds die of hunger that there’s enough space for all. The hawkish males then fall into the same trap as their female comrades during nutty seasons—they brawl, squandering precious resources with each bloody battle. But in good years, when competition for nesting territory heats up, aggression pays for the hawkish male tit bird.

During times of war or fear—the human equivalent of a bad nut season for female tit birds—it might seem that what we need most are aggressive heroic types. But if our entire population consisted of warriors, there would be no one to notice, let alone battle, potentially deadly but far quieter threats like viral disease or climate change.

Consider Vice President Al Gore’s decades-long crusade to raise awareness of global warming. Gore is, by many accounts, an introvert. “If you send an introvert into a reception or an event with a hundred other people he will emerge with less energy than he had going in,” says a former aide. “Gore needs a rest after an event.” Gore acknowledges that his skills are not conducive to stumping and speechmaking. “Most people in politics draw energy from backslapping and shaking hands and all that,” he has said. “I draw energy from discussing ideas.”

But combine that passion for thought with attention to subtlety—both common characteristics of introverts—and you get a very powerful mix. In 1968, when Gore was a college student at Harvard, he took a class with an influential oceanographer who presented early evidence linking the burning of fossil fuels with the greenhouse effect. Gore’s ears perked up.

He tried to tell others what he knew. But he found that people wouldn’t listen. It was as if they couldn’t hear the alarm bells that rang so loudly in his ears.

“When I went to Congress in the middle of the 1970s, I helped organize the first hearings on global warming,” he recalls in the Oscar-winning movie An Inconvenient Truth—a film whose most stirring action scenes involve the solitary figure of Gore wheeling his suitcase through a midnight airport. Gore seems genuinely puzzled that no one paid attention: “I actually thought and believed that the story would be compelling enough to cause a real sea change in the way Congress reacted to that issue. I thought they would be startled, too. And they weren’t.”

But if Gore had known then what we know now about Kagan’s research, and Aron’s, he might have been less surprised by his colleagues’ reactions. He might even have used his insight into personality psychology to get them to listen. Congress, he could have safely assumed, is made up of some of the least sensitive people in the country—people who, if they’d been kids in one of Kagan’s experiments, would have marched up to oddly attired clowns and strange ladies wearing gas masks without so much as a backward glance at their mothers. Remember Kagan’s introverted Tom and extroverted Ralph? Well, Congress is full of Ralphs—it was designed for people like Ralph. Most of the Toms of the world do not want to spend their days planning campaigns and schmoozing with lobbyists.

These Ralph-like Congressmen can be wonderful people—exuberant, fearless, persuasive—but they’re unlikely to feel alarmed by a photograph of a tiny crack in a distant glacier. They need more intense stimulation to get them to listen. Which is why Gore finally got his message across when he teamed up with whiz-bang Hollywood types who could package his warning into the special-effects-laden show that became An Inconvenient Truth.

Gore also drew on his own strengths, using his natural focus and diligence to tirelessly promote the movie. He visited dozens of movie theaters across the country to meet with viewers, and gave innumerable TV and radio interviews. On the subject of global warming, Gore has a clarity of voice that eluded him as a politician. For Gore, immersing himself in a complicated scientific puzzle comes naturally. Focusing on a single passion rather than tap dancing from subject to subject comes naturally. Even talking to crowds comes naturally when the topic is climate change: Gore on global warming has an easy charisma and connection with audience members that eluded him as a political candidate. That’s because this mission, for him, is not about politics or personality. It’s about the call of his conscience. “It’s about the survival of the planet,” he says. “Nobody is going to care who won or lost any election when the earth is uninhabitable.”

If you’re a sensitive sort, then you may be in the habit of pretending to be more of a politician and less cautious or single-mindedly focused than you actually are. But in this chapter I’m asking you to rethink this view. Without people like you, we will, quite literally, drown.

Back here at Walker Creek Ranch and the gathering for sensitive people, the Extrovert Ideal and its primacy of cool is turned upside down. If “cool” is low reactivity that predisposes a person to boldness or nonchalance, then the crowd that has come to meet Elaine Aron is deeply uncool.

The atmosphere is startling simply because it’s so unusual. It’s something you might find at a yoga class or in a Buddhist monastery, except that here there’s no unifying religion or worldview, only a shared temperament. It’s easy to see this when Aron delivers her speech. She has long observed that when she speaks to groups of highly sensitive people the room is more hushed and respectful than would be usual in a public gathering place, and this is true throughout her presentation. But it carries over all weekend.

I’ve never heard so many “after you’s” and “thank you’s” as I do here. During meals, which are held at long communal tables in a summer-camp style, open-air cafeteria, people plunge hungrily into searching conversations. There’s a lot of one-on-one discussion about intimate topics like childhood experiences and adult love lives, and social issues like health care and climate change; there’s not much in the way of storytelling intended to entertain. People listen carefully to each other and respond thoughtfully; Aron has noted that sensitive people tend to speak softly because that’s how they prefer others to communicate with them.

“In the rest of the world,” observes Michelle, a web designer who leans forward as if bracing herself against an imaginary blast of wind, “you make a statement and people may or may not discuss it. Here you make a statement and someone says, ‘What does that mean?’ And if you ask that question of someone else, they actually answer.”

It’s not that there’s no small talk, observes Strickland, the leader of the gathering. It’s that it comes not at the beginning of conversations but at the end. In most settings, people use small talk as a way of relaxing into a new relationship, and only once they’re comfortable do they connect more seriously. Sensitive people seem to do the reverse. They “enjoy small talk only after they’ve gone deep,” says Strickland. “When sensitive people are in environments that nurture their authenticity, they laugh and chitchat just as much as anyone else.”

On the first night we drift to our bedrooms, housed in a dormlike building. I brace myself instinctively: now’s the time when I’ll want to read or sleep, but will instead be called upon to have a pillow fight (summer camp) or play a loud and boring drinking game (college). But at Walker Creek Ranch, my roommate, a twenty-seven-year-old secretary with huge, doe-like eyes and the ambition to become an author, is happy to spend the evening writing peacefully in her journal. I do the same.

Of course, the weekend is not completely without tension. Some people are reserved to the point of appearing sullen. Sometimes the do-your-own-thing policy threatens to devolve into mutual loneliness as everyone goes their own separate ways. In fact, there is such a deficit of the social behavior we call “cool” that I begin thinking someone should be cracking jokes, stirring things up, handing out rum-and-Cokes. Shouldn’t they?

The truth is, as much as I crave breathing room for sensitive types, I enjoy hail-fellows-well-met, too. I’m glad for the “cool” among us, and I miss them this weekend. I’m starting to speak so softly that I feel like I’m putting myself to sleep. I wonder if deep down the others feel this way, too.

Tom, the software engineer and Abraham Lincoln look-alike, tells me of a former girlfriend who was always throwing open the doors of her house to friends and strangers. She was adventurous in every way: she loved new food, new sexual experiences, new people. It didn’t work out between them—Tom eventually craved the company of a partner who would focus more on their relationship and less on the outside world, and he’s happily married now to just such a woman—but he’s glad for the time with his ex-girlfriend.

As Tom talks, I think of how much I miss my husband, Ken, who’s back home in New York and not a sensitive type either, far from it. Sometimes this is frustrating: if something moves me to tears of empathy or anxiety, he’ll be touched, but grow impatient if I stay that way too long. But I also know that his tougher attitude is good for me, and I find his company endlessly delightful. I love his effortless charm. I love that he never runs out of interesting things to say. I love how he pours his heart and soul into everything he does, and everyone he loves, especially our family.

But most of all I love his way of expressing compassion. Ken may be aggressive, more aggressive in a week than I’ll be in a lifetime, but he uses it on behalf of others. Before we met, he worked for the UN in war zones all over the world, where, among other things, he conducted prisoner-of-war and detainee release negotiations. He would march into fetid jails and face down camp commanders with machine guns strapped to their chests until they agreed to release young girls who’d committed no crime other than to be female and victims of rape. After many years on the job, he went home and wrote down what he’d witnessed, in books and articles that bristled with rage. He didn’t write in the style of a sensitive person, and he made a lot of people angry. But he wrote like a person who cares, desperately.

I thought that Walker Creek Ranch would make me long for a world of the highly sensitive, a world in which everyone speaks softly and no one carries a big stick. But instead it reinforced my deeper yearning for balance. This balance, I think, is what Elaine Aron would say is our natural state of being, at least in Indo-European cultures like ours, which she observes have long been divided into “warrior kings” and “priestly advisers,” into the executive branch and the judicial branch, into bold and easy FDRs and sensitive, conscientious Eleanor Roosevelts.

7 WHY DID WALL STREET CRASH AND WARREN BUFFETT PROSPER? How Introverts and Extroverts Think (and Process Dopamine) Differently

Just after 7:30 a.m. on December 11, 2008, the year of the great stock market crash, Dr. Janice Dorn’s phone rang. The markets had opened on the East Coast to another session of carnage. Housing prices were plummeting, credit markets were frozen, and GM teetered on the brink of bankruptcy.

Dorn took the call from her bedroom, as she often does, wearing a headset and perched atop her green duvet. The room was decorated sparely. The most colorful thing in it was Dorn herself, who, with her flowing red hair, ivory skin, and trim frame, looks like a mature version of Lady Godiva. Dorn has a PhD in neuroscience, with a specialty in brain anatomy. She’s also an MD trained in psychiatry, an active trader in the gold futures market, and a “financial psychiatrist” who has counseled an estimated six hundred traders.

“Hi, Janice!” said the caller that morning, a confident-sounding man named Alan. “Do you have time to talk?”

Dr. Dorn did not have time. A day trader who prides herself on being in and out of trading positions every half hour, she was eager to start trading. But Dorn heard a desperate note in Alan’s voice. She agreed to take the call.

Alan was a sixty-year-old midwesterner who struck Dorn as a salt-of-the-earth type, hardworking and loyal. He had the jovial and assertive manner of an extrovert, and he maintained his good cheer despite the story of disaster he proceeded to tell. Alan and his wife had worked all their lives, and managed to sock away a million dollars for retirement. But four months earlier he’d gotten the idea that, despite having no experience in the markets, he should buy a hundred thousand dollars’ worth of GM stock, based on reports that the U.S. government might bail out the auto industry. He was convinced it was a no-lose investment.

After his trade went through, the media reported that the bailout might not happen after all. The market sold off GM and the stock price fell. But Alan imagined the thrill of winning big. It felt so real he could taste it. He held firm. The stock fell again, and again, and kept dropping until finally Alan decided to sell, at a big loss.

There was worse to come. When the next news cycle suggested that the bailout would happen after all, Alan got excited all over again and invested another hundred thousand dollars, buying more stock at the lower price. But the same thing happened: the bailout started looking uncertain.

Alan “reasoned” (this word is in quotation marks because, according to Dorn, conscious reasoning had little to do with Alan’s behavior) that the price couldn’t go much lower. He held on, savoring the idea of how much fun he and his wife would have spending all the money he stood to make. Again the stock went lower. When finally it hit seven dollars per share, Alan sold. And bought yet again, in a flush of exhilaration, when he heard that the bailout might happen after all …

By the time GM’s stock price fell to two dollars a share, Alan had lost seven hundred thousand dollars, or 70 percent of his family nest egg.

He was devastated. He asked Dorn if she could help recoup his losses. She could not. “It’s gone,” she told him. “You are never going to make that money back.”

He asked what he’d done wrong.

Dorn had many ideas about that. As an amateur, Alan shouldn’t have been trading in the first place. And he’d risked far too much money; he should have limited his exposure to 5 percent of his net worth, or $50,000. But the biggest problem may have been beyond Alan’s control: Dorn believed he was experiencing an excess of something psychologists call reward sensitivity.

A reward-sensitive person is highly motivated to seek rewards—from a promotion to a lottery jackpot to an enjoyable evening out with friends. Reward sensitivity motivates us to pursue goals like sex and money, social status and influence. It prompts us to climb ladders and reach for faraway branches in order to gather life’s choicest fruits.

But sometimes we’re too sensitive to rewards. Reward sensitivity on overdrive gets people into all kinds of trouble. We can get so excited by the prospect of juicy prizes, like winning big in the stock market, that we take outsized risks and ignore obvious warning signals.

Alan was presented with plenty of these signals, but was so animated by the prospect of winning big that he couldn’t see them. Indeed, he fell into a classic pattern of reward sensitivity run amok: at exactly the moments when the warning signs suggested slowing down, he sped up—dumping money he couldn’t afford to lose into a speculative series of trades.

Financial history is full of examples of players accelerating when they should be braking. Behavioral economists have long observed that executives buying companies can get so excited about beating out their competitors that they ignore signs that they’re overpaying. This happens so frequently that it has a name: “deal fever,” followed by “the winner’s curse.” The AOL–Time Warner merger, which wiped out $200 billion of Time Warner shareholder value, is a classic example. There were plenty of warnings that AOL’s stock, which was the currency for the merger, was wildly overvalued, yet Time Warner’s directors approved the deal unanimously.

“I did it with as much or more excitement and enthusiasm as I did when I first made love some forty-two years ago,” exclaimed Ted Turner, one of those directors and the largest individual shareholder in the company. “TED TURNER: IT’S BETTER THAN SEX,” announced the New York Post the day after the deal was struck, a headline to which we’ll return for its power to explain why smart people can sometimes be too reward-sensitive.

You may be wondering what all this has to do with introversion and extroversion. Don’t we all get a little carried away sometimes?

The answer is yes, except that some of us do so more than others. Dorn has observed that her extroverted clients are more likely to be highly reward-sensitive, while the introverts are more likely to pay attention to warning signals. They’re more successful at regulating their feelings of desire or excitement. They protect themselves better from the downside. “My introvert traders are much more able to say, ‘OK, Janice, I do feel these excited emotions coming up in me, but I understand that I can’t act on them.’ The introverts are much better at making a plan, staying with a plan, being very disciplined.”

To understand why introverts and extroverts might react differently to the prospect of rewards, says Dorn, you have to know a little about brain structure. As we saw in chapter 4, our limbic system, which we share with the most primitive mammals and which Dorn calls the “old brain,” is emotional and instinctive. It comprises various structures, including the amygdala, and it’s highly interconnected with the nucleus accumbens, sometimes called the brain’s “pleasure center.” We examined the anxious side of the old brain when we explored the role of the amygdala in high reactivity and introversion. Now we’re about to see its greedy side.

The old brain, according to Dorn, is constantly telling us, “Yes, yes, yes! Eat more, drink more, have more sex, take lots of risk, go for all the gusto you can get, and above all, do not think!” The reward-seeking, pleasure-loving part of the old brain is what Dorn believes spurred Alan to treat his life savings like chips at the casino.

We also have a “new brain” called the neocortex, which evolved many thousands of years after the limbic system. The new brain is responsible for thinking, planning, language, and decision-making—some of the very faculties that make us human. Although the new brain also plays a significant role in our emotional lives, it’s the seat of rationality. Its job, according to Dorn, includes saying, “No, no, no! Don’t do that, because it’s dangerous, makes no sense, and is not in your best interests, or those of your family, or of society.”

So where was Alan’s neocortex when he was chasing stock market gains?

The old brain and the new brain do work together, but not always efficiently. Sometimes they’re actually in conflict, and then our decisions are a function of which one is sending out stronger signals. So when Alan’s old brain sent its breathless messages up to his new brain, it probably responded as a neocortex should: it told his old brain to slow down. It said, Watch out! But it lost the ensuing tug-of-war.

We all have old brains, of course. But just as the amygdala of a high-reactive person is more sensitive than average to novelty, so do extroverts seem to be more susceptible than introverts to the reward-seeking cravings of the old brain. In fact, some scientists are starting to explore the idea that reward-sensitivity is not only an interesting feature of extroversion; it is what makes an extrovert an extrovert. Extroverts, in other words, are characterized by their tendency to seek rewards, from top dog status to sexual highs to cold cash. They’ve been found to have greater economic, political, and hedonistic ambitions than introverts; even their sociability is a function of reward-sensitivity, according to this view—extroverts socialize because human connection is inherently gratifying.

What underlies all this reward-seeking? The key seems to be positive emotion. Extroverts tend to experience more pleasure and excitement than introverts do—emotions that are activated, explains the psychologist Daniel Nettle in his illuminating book on personality, “in response to the pursuit or capture of some resource that is valued. Excitement builds towards the anticipated capture of that resource. Joy follows its capture.” Extroverts, in other words, often find themselves in an emotional state we might call “buzz”—a rush of energized, enthusiastic feelings. This is a sensation we all know and like, but not necessarily to the same degree or with the same frequency: extroverts seem to get an extra buzz from the pursuit and attainment of their goals.

The basis of buzz appears to be a high degree of activity in a network of structures in the brain—often called the “reward system”—including the orbitofrontal cortex, the nucleus accumbens, and the amygdala. The job of the reward system is to get us excited about potential goodies; fMRI experiments have shown that the system is activated by any number of possible delights, from anticipation of a squirt of Kool-Aid on the tongue, to money, to pictures of attractive people.

The neurons that transmit information in the reward network operate in part through a neurotransmitter—a chemical that carries information between brain cells—called dopamine. Dopamine is the “reward chemical” released in response to anticipated pleasures. The more responsive your brain is to dopamine, or the higher the level of dopamine you have available to release, some scientists believe, the more likely you are to go after rewards like sex, chocolate, money, and status. Stimulating mid-brain dopamine activity in mice gets them to run around excitedly in an empty cage until they drop dead of starvation. Cocaine and heroin, which stimulate dopamine-releasing neurons in humans, make people euphoric.

Extroverts’ dopamine pathways appear to be more active than those of introverts. Although the exact relationship between extroversion, dopamine, and the brain’s reward system has not been conclusively established, early findings have been intriguing. In one experiment, Richard Depue, a neurobiologist at Cornell University, gave an amphetamine that activates the dopamine system to a group of introverts and extroverts, and found that the extroverts had a stronger response. Another study found that extroverts who win gambling games have more activity in the reward-sensitive regions of their brains than victorious introverts do. Still other research has shown that the medial orbitofrontal cortex, a key component of the brain’s dopamine-driven reward system, is larger in extroverts than in introverts.

By contrast, introverts “have a smaller response” in the reward system, writes psychologist Nettle, “and so go less out of their way to follow up [reward] cues.” They will, “like anyone, be drawn from time to time to sex, and parties, and status, but the kick they get will be relatively small, so they are not going to break a leg to get there.” In short, introverts just don’t buzz as easily.

In some ways, extroverts are lucky; buzz has a delightful champagne-bubble quality. It fires us up to work and play hard. It gives us the courage to take chances. Buzz also gets us to do things that would otherwise seem too difficult, like giving speeches. Imagine you work hard to prepare a talk on a subject you care about. You get your message across, and when you finish the audience rises to its feet, its clapping sustained and sincere. One person might leave the room feeling, “I’m glad I got my message across, but I’m also happy it’s over; now I can get back to the rest of my life.” Another person, more sensitive to buzz, might walk away feeling, “What a trip! Did you hear that applause? Did you see the expression on their faces when I made that life-changing point? This is great!”

But buzz also has considerable downsides. “Everyone assumes that it’s good to accentuate positive emotions, but that isn’t correct,” the psychology professor Richard Howard told me, pointing to the example of soccer victories that end in violence and property damage. “A lot of antisocial and self-defeating behavior results from people who amplify positive emotions.”

Another disadvantage of buzz may be its connection to risk—sometimes outsized risk. Buzz can cause us to ignore warning signs we should be heeding. When Ted Turner (who appears to be an extreme extrovert) compared the AOL–Time Warner deal to his first sexual experience, he may have been telling us that he was in the same buzzy state of mind as an adolescent who’s so excited about spending the night with his new girlfriend that he’s not thinking much about the consequences. This blindness to danger may explain why extroverts are more likely than introverts to be killed while driving, be hospitalized as a result of accident or injury, smoke, have risky sex, participate in high-risk sports, have affairs, and remarry. It also helps explain why extroverts are more prone than introverts to overconfidence—defined as greater confidence unmatched by greater ability. Buzz is JFK’s Camelot, but it’s also the Kennedy Curse.

This theory of extroversion is still young, and it is not absolute. We can’t say that all extroverts constantly crave rewards or that all introverts always brake for trouble. Still, the theory suggests that we should rethink the roles that introverts and extroverts play in their own lives, and in organizations. It suggests that when it comes time to make group decisions, extroverts would do well to listen to introverts—especially when they see problems ahead.

In the wake of the 2008 crash, a financial catastrophe caused in part by uncalculated risk-taking and blindness to threat, it became fashionable to speculate whether we’d have been better off with more women and fewer men—or less testosterone—on Wall Street. But maybe we should also ask what might have happened with a few more introverts at the helm—and a lot less dopamine.

Several studies answer this question implicitly. Kellogg School of Management Professor Camelia Kuhnen has found that the variation of a dopamine-regulating gene (DRD4) associated with a particularly thrill-seeking version of extroversion is a strong predictor of financial risk-taking. By contrast, people with a variant of a serotonin-regulating gene linked to introversion and sensitivity take 28 percent less financial risk than others. They have also been found to outperform their peers when playing gambling games calling for sophisticated decision-making. (When faced with a low probability of winning, people with this gene variant tend to be risk-averse; when they have a high probability of winning, they become relatively risk-seeking.) Another study, of sixty-four traders at an investment bank, found that the highest-performing traders tended to be emotionally stable introverts.

Introverts also seem to be better than extroverts at delaying gratification, a crucial life skill associated with everything from higher SAT scores and income to lower body mass index. In one study, scientists gave participants the choice of a small reward immediately (a gift certificate from Amazon) or a bigger gift certificate in two to four weeks. Objectively, the bigger reward in the near but not immediate future was the more desirable option. But many people went for the “I want it now” choice—and when they did, a brain scanner revealed that their reward network was activated. Those who held out for the larger reward two weeks hence showed more activity in the prefrontal cortex—the part of the new brain that talks us out of sending ill-considered e-mails and eating too much chocolate cake. (A similar study suggests that the former group tended to be extroverts and the latter group introverts.)

Back in the 1990s, when I was a junior associate at a Wall Street law firm, I found myself on a team of lawyers representing a bank considering buying a portfolio of subprime mortgage loans made by other lenders. My job was to perform due diligence—to review the documentation to see whether the loans had been made with the proper paperwork. Had the borrowers been notified of the interest rates they were slated to pay? That the rates would go up over time?

The papers turned out to be chock-full of irregularities. If I’d been in the bankers’ shoes, this would have made me nervous, very nervous. But when our legal team summarized the risks in a caution-filled conference call, the bankers seemed utterly untroubled. They saw the potential profits of buying those loans at a discount, and they wanted to go ahead with the deal. Yet it was just this kind of risk-reward miscalculation that contributed to the failure of many banks during the Great Recession of 2008.

At about the same time I evaluated that portfolio of loans, I heard a story circulating on Wall Street about a competition among investment banks for a prestigious piece of business. Each of the major banks sent a squad of their top employees to pitch the client. Each team deployed the usual tools: spread sheets, “pitch books,” and PowerPoint presentations. But the winning team added its own piece of theatrics: they ran into the room wearing matching baseball caps and T-shirts emblazoned with the letters FUD, an acronym for Fear, Uncertainty, and Doubt. In this case FUD had been crossed out with an emphatic red X; FUD was an unholy trinity. That team, the vanquishers of FUD, won the contest.

Disdain for FUD—and for the type of person who tends to experience it—is what helped cause the crash, says Boykin Curry, a managing director of the investment firm Eagle Capital, who had front-row seats to the 2008 meltdown. Too much power was concentrated in the hands of aggressive risk-takers. “For twenty years, the DNA of nearly every financial institution … morphed dangerously,” he told Newsweek magazine at the height of the crash. “Each time someone at the table pressed for more leverage and more risk, the next few years proved them ‘right.’ These people were emboldened, they were promoted and they gained control of ever more capital. Meanwhile, anyone in power who hesitated, who argued for caution, was proved ‘wrong.’ The cautious types were increasingly intimidated, passed over for promotion. They lost their hold on capital. This happened every day in almost every financial institution, over and over, until we ended up with a very specific kind of person running things.”

Curry is a Harvard Business School grad and, with his wife, Celerie Kemble, a Palm Beach–born designer, a prominent fixture on New York political and social scenes. Which is to say that he would seem to be a card-carrying member of what he calls the “go-go aggressive” crowd, and an unlikely advocate for the importance of introverts. But one thing he’s not shy about is his thesis that it was forceful extroverts who caused the global financial crash.

“People with certain personality types got control of capital and institutions and power,” Curry told me. “And people who are congenitally more cautious and introverted and statistical in their thinking became discredited and pushed aside.”

Vincent Kaminski, a Rice University business school professor who once served as managing director of research for Enron, the company that famously filed for bankruptcy in 2001 as a result of reckless business practices, told the Washington Post a similar story of a business culture in which aggressive risk-takers enjoyed too high a status relative to cautious introverts. Kaminski, a soft-spoken and careful man, was one of the few heroes of the Enron scandal. He repeatedly tried to sound the alarm with senior management that the company had entered into business deals risky enough to threaten its survival. When the top brass wouldn’t listen, he refused to sign off on these dangerous transactions and ordered his team not to work on them. The company stripped him of his power to review company-wide deals.

“There have been some complaints, Vince, that you’re not helping people to do transactions,” the president of Enron told him, according to Conspiracy of Fools, a book about the Enron scandal. “Instead, you’re spending all your time acting like cops. We don’t need cops, Vince.”

But they did need them, and still do. When the credit crisis threatened the viability of some of Wall Street’s biggest banks in 2007, Kaminski saw the same thing happening all over again. “Let’s just say that all the demons of Enron have not been exorcised,” he told the Post in November of that year. The problem, he explained, was not only that many had failed to understand the risks the banks were taking. It was also that those who did understand were consistently ignored—in part because they had the wrong personality style: “Many times I have been sitting across the table from an energy trader and I would say, ‘Your portfolio will implode if this specific situation happens.’ And the trader would start yelling at me and telling me I’m an idiot, that such a situation would never happen. The problem is that, on one side, you have a rainmaker who is making lots of money for the company and is treated like a superstar, and on the other side you have an introverted nerd. So who do you think wins?”

But what exactly is the mechanism by which buzz clouds good judgment? How did Janice Dorn’s client, Alan, dismiss the danger signs screaming that he might lose 70 percent of his life savings? What prompts some people to act as if FUD doesn’t exist?

One answer comes from an intriguing line of research conducted by the University of Wisconsin psychologist Joseph Newman. Imagine that you’ve been invited to Newman’s lab to participate in one of his studies. You’re there to play a game: the more points you get, the more money you win. Twelve different numbers flash across a computer screen, one at a time, in no particular order. You’re given a button, as if you were a game-show contestant, which you can press or not as each number appears. If you press the button for a “good” number, you win points; if you press for a “bad” number, you lose points; and if you don’t press at all, nothing happens. Through trial and error you learn that four is a nice number and nine is not. So the next time the number nine flashes across your screen, you know not to press that button.

Except that sometimes people press the button for the bad numbers, even when they should know better. Extroverts, especially highly impulsive extroverts, are more likely than introverts to make this mistake. Why? Well, in the words of psychologists John Brebner and Chris Cooper, who have shown that extroverts think less and act faster on such tasks: introverts are “geared to inspect” and extroverts “geared to respond.”

But the more interesting aspect of this puzzling behavior is not what the extroverts do before they’ve hit the wrong button, but what they do after. When introverts hit the number nine button and find they’ve lost a point, they slow down before moving on to the next number, as if to reflect on what went wrong. But extroverts not only fail to slow down, they actually speed up.

This seems strange; why would anyone do this? Newman explains that it makes perfect sense. If you focus on achieving your goals, as reward-sensitive extroverts do, you don’t want anything to get in your way—neither naysayers nor the number nine. You speed up in an attempt to knock these roadblocks down.

Yet this is a crucially important misstep, because the longer you pause to process surprising or negative feedback, the more likely you are to learn from it. If you force extroverts to pause, says Newman, they’ll do just as well as introverts at the numbers game. But, left to their own devices, they don’t stop. And so they don’t learn to avoid the trouble staring them in the face. Newman says that this is exactly what might happen to extroverts like Ted Turner when bidding for a company on auction. “When a person bids up too high,” he told me, “that’s because they didn’t inhibit a response they should have inhibited. They didn’t consider information that should have been weighing on their decision.”

Introverts, in contrast, are constitutionally programmed to downplay reward—to kill their buzz, you might say—and scan for problems. “As soon they get excited,” says Newman, “they’ll put the brakes on and think about peripheral issues that may be more important. Introverts seem to be specifically wired or trained so when they catch themselves getting excited and focused on a goal, their vigilance increases.”

Introverts also tend to compare new information with their expectations, he says. They ask themselves, “Is this what I thought would happen? Is it how it should be?” And when the situation falls short of expectations, they form associations between the moment of disappointment (losing points) and whatever was going on in their environment at the time of the disappointment (hitting the number nine.) These associations let them make accurate predictions about how to react to warning signals in the future.

Introverts’ disinclination to charge ahead is not only a hedge against risk; it also pays off on intellectual tasks. Here are some of the things we know about the relative performance of introverts and extroverts at complex problem-solving. Extroverts get better grades than introverts during elementary school, but introverts outperform extroverts in high school and college. At the university level, introversion predicts academic performance better than cognitive ability. One study tested 141 college students’ knowledge of twenty different subjects, from art to astronomy to statistics, and found that introverts knew more than the extroverts about every single one of them. Introverts receive disproportionate numbers of graduate degrees, National Merit Scholarship finalist positions, and Phi Beta Kappa keys. They outperform extroverts on the Watson-Glaser Critical Thinking Appraisal test, an assessment of critical thinking widely used by businesses for hiring and promotion. They’ve been shown to excel at something psychologists call “insightful problem solving.”

The question is: Why?

Introverts are not smarter than extroverts. According to IQ scores, the two types are equally intelligent. And on many kinds of tasks, particularly those performed under time or social pressure or involving multitasking, extroverts do better. Extroverts are better than introverts at handling information overload. Introverts’ reflectiveness uses up a lot of cognitive capacity, according to Joseph Newman. On any given task, he says, “if we have 100 percent cognitive capacity, an introvert may have only 75 percent on task and 25 percent off task, whereas an extrovert may have 90 percent on task.” This is because most tasks are goal-directed. Extroverts appear to allocate most of their cognitive capacity to the goal at hand, while introverts use up capacity by monitoring how the task is going.

But introverts seem to think more carefully than extroverts, as the psychologist Gerald Matthews describes in his work. Extroverts are more likely to take a quick-and-dirty approach to problem-solving, trading accuracy for speed, making increasing numbers of mistakes as they go, and abandoning ship altogether when the problem seems too difficult or frustrating. Introverts think before they act, digest information thoroughly, stay on task longer, give up less easily, and work more accurately. Introverts and extroverts also direct their attention differently: if you leave them to their own devices, the introverts tend to sit around wondering about things, imagining things, recalling events from their past, and making plans for the future. The extroverts are more likely to focus on what’s happening around them. It’s as if extroverts are seeing “what is” while their introverted peers are asking “what if.”

Introverts’ and extroverts’ contrasting problem-solving styles have been observed in many different contexts. In one experiment, psychologists gave fifty people a difficult jigsaw puzzle to solve, and found that the extroverts were more likely than the introverts to quit midway. In another, Professor Richard Howard gave introverts and extroverts a complicated series of printed mazes, and found not only that the introverts tended to solve more mazes correctly, but also that they spent a much greater percentage of their allotted time inspecting the maze before entering it. A similar thing happened when groups of introverts and extroverts were given the Raven Standard Progressive Matrices, an intelligence test that consists of five sets of problems of increasing difficulty. The extroverts tended to do better on the first two sets, presumably because of their ability to orient quickly to their goal. But on the three more difficult sets, where persistence pays, the introverts significantly outperformed them. By the final, most complicated set, the extroverts were much more likely than the introverts to abandon the task altogether.

Introverts sometimes outperform extroverts even on social tasks that require persistence. Wharton management professor Adam Grant (who conducted the leadership studies described in chapter 2) once studied the personality traits of effective call-center employees. Grant predicted that the extroverts would be better telemarketers, but it turned out that there was zero correlation between extroversion levels and cold-calling prowess.

“The extroverts would make these wonderful calls,” Grant told me, “but then a shiny object of some kind would cross their paths and they’d lose focus.” The introverts, in contrast, “would talk very quietly, but boom, boom, boom, they were making those calls. They were focused and determined.” The only extroverts to outperform them were those who also happened to be unusually high scorers for a separate personality trait measuring conscientiousness. Introvert persistence was more than a match for extrovert buzz, in other words, even at a task where social skills might be considered at a premium.

Persistence isn’t very glamorous. If genius is one percent inspiration and ninety-nine percent perspiration, then as a culture we tend to lionize the one percent. We love its flash and dazzle. But great power lies in the other ninety-nine percent.

“It’s not that I’m so smart,” said Einstein, who was a consummate introvert. “It’s that I stay with problems longer.”

None of this is to denigrate those who forge ahead quickly, or to blindly glorify the reflective and careful. The point is that we tend to overvalue buzz and discount the risks of reward-sensitivity: we need to find a balance between action and reflection.

For example, if you were staffing an investment bank, management professor Kuhnen told me, you’d want to hire not only reward-sensitive types, who are likely to profit from bull markets, but also those who remain emotionally more neutral. You’d want to make sure that important corporate decisions reflect the input of both kinds of people, not just one type. And you’d want to know that individuals on all points of the reward-sensitivity spectrum understand their own emotional preferences and can temper them to match market conditions.

But it’s not just employers who benefit from taking a closer look at their employees. We also need to take a closer look at ourselves. Understanding where we fall on the reward-sensitivity spectrum gives us the power to live our lives well.

If you’re a buzz-prone extrovert, then you’re lucky to enjoy lots of invigorating emotions. Make the most of them: build things, inspire others, think big. Start a company, launch a website, build an elaborate tree house for your kids. But also know that you’re operating with an Achilles’ heel that you must learn to protect. Train yourself to spend energy on what’s truly meaningful to you instead of on activities that look like they’ll deliver a quick buzz of money or status or excitement. Teach yourself to pause and reflect when warning signs appear that things aren’t working out as you’d hoped. Learn from your mistakes. Seek out counterparts (from spouses to friends to business partners) who can help rein you in and compensate for your blind spots.

And when it comes time to invest, or to do anything that involves a sage balance of risk and reward, keep yourself in check. One good way to do this is to make sure that you’re not surrounding yourself with images of reward at the crucial moment of decision. Kuhnen and Brian Knutson have found that men who are shown erotic pictures just before they gamble take more risks than those shown neutral images like desks and chairs. This is because anticipating rewards—any rewards, whether or not related to the subject at hand—excites our dopamine-driven reward networks and makes us act more rashly. (This may be the single best argument yet for banning pornography from workplaces.)

And if you’re an introvert who’s relatively immune to the excesses of reward sensitivity? At first blush, the research on dopamine and buzz seems to imply that extroverts, and extroverts alone, are happily motivated to work hard by the excitement they get from pursuing their goals. As an introvert, I was puzzled by this idea when I first came across it. It didn’t reflect my own experience. I’m in love with my work and always have been. I wake up in the morning excited to get started. So what drives people like me?

One answer is that even if the reward-sensitivity theory of extroversion turns out to be correct, we can’t say that all extroverts are always more sensitive to rewards and blasé about risk, or that all introverts are constantly unmoved by incentives and vigilant about threats. Since the days of Aristotle, philosophers have observed that these two modes—approaching things that appear to give pleasure and avoiding others that seem to cause pain—lie at the heart of all human activity. As a group, extroverts tend to be reward-seeking, but every human being has her own mix of approach and avoidance tendencies, and sometimes the combination differs depending on the situation. Indeed, many contemporary personality psychologists would say that threat-vigilance is more characteristic of a trait known as “neuroticism” than of introversion. The body’s reward and threat systems also seem to work independently of each other, so that the same person can be generally sensitive, or insensitive, to both reward and threat.

If you want to determine whether you are reward-oriented, threat-oriented, or both, try asking yourself whether the following groups of statements are true of you.

If you are reward-oriented:

1. When I get something I want, I feel excited and energized.

2. When I want something, I usually go all out to get it.

3. When I see an opportunity for something I like, I get excited right away.

4. When good things happen to me, it affects me strongly.

5. I have very few fears compared to my friends.

If you are threat-oriented:

1. Criticism or scolding hurts me quite a bit.

2. I feel pretty worried or upset when I think or know somebody is angry at me.

3. If I think something unpleasant is going to happen, I usually get pretty “worked up.”

4. I feel worried when I think I have done poorly at something important.

5. I worry about making mistakes.

But I believe that another important explanation for introverts who love their work may come from a very different line of research by the influential psychologist Mihaly Csikszentmihalyi on the state of being he calls “flow.” Flow is an optimal state in which you feel totally engaged in an activity—whether long-distance swimming or songwriting, sumo wrestling or sex. In a state of flow, you’re neither bored nor anxious, and you don’t question your own adequacy. Hours pass without your noticing.

The key to flow is to pursue an activity for its own sake, not for the rewards it brings. Although flow does not depend on being an introvert or an extrovert, many of the flow experiences that Csikszentmihalyi writes about are solitary pursuits that have nothing to do with reward-seeking: reading, tending an orchard, solo ocean cruising. Flow often occurs, he writes, in conditions in which people “become independent of the social environment to the degree that they no longer respond exclusively in terms of its rewards and punishments. To achieve such autonomy, a person has to learn to provide rewards to herself.”

In a sense, Csikszentmihalyi transcends Aristotle; he is telling us that there are some activities that are not about approach or avoidance, but about something deeper: the fulfillment that comes from absorption in an activity outside yourself. “Psychological theories usually assume that we are motivated either by the need to eliminate an unpleasant condition like hunger or fear,” Csikszentmihalyi writes, “or by the expectation of some future reward such as money, status, or prestige.” But in flow, “a person could work around the clock for days on end, for no better reason than to keep on working.”

If you’re an introvert, find your flow by using your gifts. You have the power of persistence, the tenacity to solve complex problems, and the clear-sightedness to avoid pitfalls that trip others up. You enjoy relative freedom from the temptations of superficial prizes like money and status. Indeed, your biggest challenge may be to fully harness your strengths. You may be so busy trying to appear like a zestful, reward-sensitive extrovert that you undervalue your own talents, or feel underestimated by those around you. But when you’re focused on a project that you care about, you probably find that your energy is boundless.

So stay true to your own nature. If you like to do things in a slow and steady way, don’t let others make you feel as if you have to race. If you enjoy depth, don’t force yourself to seek breadth. If you prefer single-tasking to multitasking, stick to your guns. Being relatively unmoved by rewards gives you the incalculable power to go your own way. It’s up to you to use that independence to good effect.

Of course, that isn’t always easy. While writing this chapter, I corresponded with Jack Welch, the former chairman of General Electric. He had just published a BusinessWeek online column called “Release Your Inner Extrovert,” in which he called for introverts to act more extroverted on the job. I suggested that extroverts sometimes need to act more introverted, too, and shared with him some of the ideas you’ve just read about how Wall Street might have benefited from having more introverts at the helm. Welch was intrigued. But, he said, “the extroverts would argue that they never heard from the introverts.”

Welch makes a fair point. Introverts need to trust their gut and share their ideas as powerfully as they can. This does not mean aping extroverts; ideas can be shared quietly, they can be communicated in writing, they can be packaged into highly produced lectures, they can be advanced by allies. The trick for introverts is to honor their own styles instead of allowing themselves to be swept up by prevailing norms. The story of the lead-up to the Great Recession of 2008 is peppered, alas, with careful types who took inappropriate risks, like the former chief executive of Citigroup, Chuck Prince, a former lawyer who made risky loans into a falling market because, he said, “as long as the music is playing, you’ve got to get up and dance.”

“People who are initially cautious become more aggressive,” observes Boykin Curry of this phenomenon. “They say, ‘Hey, the more aggressive people are getting promoted and I’m not, so I’m going to be more aggressive too.’ ”

But stories of financial crises often contain subplots about people who famously (and profitably) saw them coming—and such tales tend to feature just the kinds of people who embrace FUD, or who like to close the blinds to their offices, insulate themselves from mass opinion and peer pressure, and focus in solitude. One of the few investors who managed to flourish during the crash of 2008 was Seth Klarman, president of a hedge fund called the Baupost Group. Klarman is known for consistently outperforming the market while steadfastly avoiding risk, and for keeping a significant percentage of his assets in cash. In the two years since the crash of 2008, when most investors were fleeing hedge funds in droves, Klarman almost doubled Baupost’s assets under management to $22 billion.

Klarman achieved this with an investment strategy based explicitly on FUD. “At Baupost, we are big fans of fear, and in investing, it is clearly better to be scared than sorry,” he once wrote in a letter to investors. Klarman is a “world-class worrier,” observes the New York Times, in a 2007 article called “Manager Frets Over the Market, But Still Outdoes It.” He owns a racehorse called “Read the Footnotes.”

During the years leading up to the 2008 crash, Klarman “was one of the few people to stick to a cautious and seemingly paranoid message,” says Boykin Curry. “When everyone else was celebrating, he was probably storing cans of tuna in his basement, to prepare for the end of civilization. Then, when everyone else panicked, he started buying. It’s not just analysis; it’s his emotional makeup. The same wiring that helps Seth find opportunities that no one else sees can make him seem aloof or blunt. If you’re the kind of person who frets every time the quarter is good, you may have trouble rising to the top of a corporate pyramid. Seth probably wouldn’t have made it as a sales manager. But he is one of the great investors of our time.”

Similarly, in his book on the run-up to the 2008 crash, The Big Short, Michael Lewis introduces three of the few people who were astute enough to forecast the coming disaster. One was a solitary hedge-fund manager named Michael Burry who describes himself as “happy in my own head” and who spent the years prior to the crash alone in his office in San Jose, California, combing through financial documents and developing his own contrarian views of market risk. The others were a pair of socially awkward investors named Charlie Ledley and Jamie Mai, whose entire investment strategy was based on FUD: they placed bets that had limited downside, but would pay off handsomely if dramatic but unexpected changes occurred in the market. It was not an investment strategy so much as a life philosophy—a belief that most situations were not as stable as they appeared to be.

This “suited the two men’s personalities,” writes Lewis. “They never had to be sure of anything. Both were predisposed to feel that people, and by extension markets, were too certain about inherently uncertain things.” Even after being proven right with their 2006 and 2007 bets against the subprime mortgage market, and earning $100 million in the process, “they actually spent time wondering how people who had been so sensationally right (i.e., they themselves) could preserve the capacity for diffidence and doubt and uncertainty that had enabled them to be right.”

Ledley and Mai understood the value of their constitutional diffidence, but others were so spooked by it that they gave up the chance to invest money with the two—in effect, sacrificing millions of dollars to their prejudice against FUD. “What’s amazing with Charlie Ledley,” says Boykin Curry, who knows him well, “is that here you had a brilliant investor who was exceedingly conservative. If you were concerned about risk, there was no one better to go to. But he was terrible at raising capital because he seemed so tentative about everything. Potential clients would walk out of Charlie’s office scared to give him money because they thought he lacked conviction. Meanwhile, they poured money into funds run by managers who exuded confidence and certainty. Of course, when the economy turned, the confident group lost half their clients’ money, while Charlie and Jamie made a fortune. Anyone who used conventional social cues to evaluate money managers was led to exactly the wrong conclusion.”

Another example, this one from the 2000 crash of the dot-com bubble, concerns a self-described introvert based in Omaha, Nebraska, where he’s well known for shutting himself inside his office for hours at a time.

Warren Buffett, the legendary investor and one of the wealthiest men in the world, has used exactly the attributes we’ve explored in this chapter—intellectual persistence, prudent thinking, and the ability to see and act on warning signs—to make billions of dollars for himself and the shareholders in his company, Berkshire Hathaway. Buffett is known for thinking carefully when those around him lose their heads. “Success in investing doesn’t correlate with IQ,” he has said. “Once you have ordinary intelligence, what you need is the temperament to control the urges that get other people into trouble in investing.”

Every summer since 1983, the boutique investment bank Allen & Co. has hosted a weeklong conference in Sun Valley, Idaho. This isn’t just any conference. It’s an extravaganza, with lavish parties, river-rafting trips, ice-skating, mountain biking, fly fishing, horseback riding, and a fleet of babysitters to care for guests’ children. The hosts service the media industry, and past guest lists have included newspaper moguls, Hollywood celebrities, and Silicon Valley stars, with marquee names such as Tom Hanks, Candice Bergen, Barry Diller, Rupert Murdoch, Steve Jobs, Diane Sawyer, and Tom Brokaw.

In July 1999, according to Alice Schroeder’s excellent biography of Buffett, The Snowball, he was one of those guests. He had attended year after year with his entire family in tow, arriving by Gulfstream jet and staying with the other VIP attendees in a select group of condos overlooking the golf course. Buffett loved his annual vacation at Sun Valley, regarding it as a great place for his family to gather and for him to catch up with old friends.

But this year the mood was different. It was the height of the technology boom, and there were new faces at the table—the heads of technology companies that had grown rich and powerful almost overnight, and the venture capitalists who had fed them cash. These people were riding high. When the celebrity photographer Annie Leibovitz showed up to shoot “the Media All-Star Team” for Vanity Fair, some of them lobbied to get in the photo. They were the future, they believed.

Buffett was decidedly not a part of this group. He was an old-school investor who didn’t get caught up in speculative frenzy around companies with unclear earnings prospects. Some dismissed him as a relic of the past. But Buffett was still powerful enough to give the keynote address on the final day of the conference.

He thought long and hard about that speech and spent weeks preparing for it. After warming up the crowd with a charmingly self-deprecating story—Buffett used to dread public speaking until he took a Dale Carnegie course—he told the crowd, in painstaking, brilliantly analyzed detail, why the tech-fueled bull market wouldn’t last. Buffett had studied the data, noted the danger signals, and then paused and reflected on what they meant. It was the first public forecast he had made in thirty years.

The audience wasn’t thrilled, according to Schroeder. Buffett was raining on their parade. They gave him a standing ovation, but in private, many dismissed his ideas. “Good old Warren,” they said. “Smart man, but this time he missed the boat.”

Later that evening, the conference wrapped up with a glorious display of fireworks. As always, it had been a blazing success. But the most important aspect of the gathering—Warren Buffett alerting the crowd to the market’s warning signs—wouldn’t be revealed until the following year, when the dot-com bubble burst, just as he said it would.

Buffett takes pride not only in his track record, but also in following his own “inner scorecard.” He divides the world into people who focus on their own instincts and those who follow the herd. “I feel like I’m on my back,” says Buffett about his life as an investor, “and there’s the Sistine Chapel, and I’m painting away. I like it when people say, ‘Gee, that’s a pretty good-looking painting.’ But it’s my painting, and when somebody says, ‘Why don’t you use more red instead of blue?’ Good-bye. It’s my painting. And I don’t care what they sell it for. The painting itself will never be finished. That’s one of the great things about it.”