If you're an introvert, you also know that the bias against quiet can cause deep psychic pain. As a child you might have overheard your parents apologize for your shyness. ("Why can't you be more like the Kennedy boys?" the Camelot-besotted parents of one man I interviewed repeatedly asked him.) Or at school you might have been prodded to come "out of your shell" - that noxious expression which fails to appreciate that some animals naturally carry shelter everywhere they go, and that some humans are just the same. "All the comments from childhood still ring in my ears, that I was lazy, stupid, slow, boring," writes a member of an e-mail list called Introvert Retreat. "By the time I was old enough to figure out that I was simply introverted , it was a part of my being, the assumption that there is something inherently wrong with me. I wish I could find that little vestige of doubt and remove it."
Now that you're an adult, you might still feel a pang of guilt when you decline a dinner invitation in favor of a good book. Or maybe you like to eat alone in restaurants and could do without the pitying looks from fellow diners. Or you're told that you're "in your head too much," a phrase that's often deployed against the quiet and cerebral.
Of course, there's another word for such people: thinkers.

Many introverts are also "highly sensitive," which sounds poetic, but is actually a technical term in psychology. If you are a sensitive sort, then you're more apt than the average person to feel pleasantly overwhelmed by Beethoven's "Moonlight Sonata" or a well-turned phrase or an act of extraordinary kindness. You may be quicker than others to feel sickened by violence and ugliness, and you likely have a very strong conscience. When you were a child you were probably called "shy," and to this day feel nervous when you're being evaluated, for example when giving a speech or on a first date. Later we'll examine why this seemingly unrelated collection of attributes tends to belong to the same person and why this person is often introverted. (No one knows exactly how many introverts are highly sensitive, but we know that 70 percent of sensitives are introverts, and the other 30 percent tend to report needing a lot of "down time.")

A well-known study out of UC Berkeley by organizational behavior professor Philip Tetlock found that television pundits - that is, people who earn their livings by holding forth confidently on the basis of limited information - make worse predictions about political and economic trends than they would by random chance. And the very worst prognosticators tend to be the most famous and the most confident - the very ones who would be considered natural leaders in an HBS classroom.
The U.S. Army has a name for a similar phenomenon: "the Bus to Abilene." "Any army officer can tell you what that means," Colonel (Ret.) Stephen J. Gerras, a professor of behavioral sciences at the U.S. Army War College, told Yale Alumni Magazine in 2008. It's about a family sitting on a porch in Texas on a hot summer day, and somebody says, "I'm bored. Why don't we go to Abilene?" When they get to Abilene, somebody says, "You know, I didn't really want to go." And the next person says. "I didn't want to go - I thought you wanted to go," and so on. Whenever you're in an army group and somebody says, "I think we're all getting on the bus to Abilene here," that is a red flag. You can stop a conversation with it. It is a very powerful artifact of our culture."

Studies have shown that, indeed, introverts are more likely than extroverts to express intimate facts about themselves online that their family and friends would be surprised to read, to say that they can express the "real me" online, and to spend more time in certain kinds of online discussions. They welcome the chance to communicate digitally. The same person who would never raise his hand in a lecture hall of two hundred people might blog to two thousand, or two million, without thinking twice. The same person who finds it difficult to introduce himself to strangers might establish a presence online and then extend these relationships into the real world.

Carnegie's metamorphosis from farmboy to salesman to public-speaking icon is also the story of the rise of the Extrovert Ideal. Carnegie's journey reflected a cultural evolution that reached a tipping point around the turn of the twentieth century, changing forever who we are and whom we admire, how we act at job interviews and what we look for in an employee, how we court our mates and raise our children. America had shifted from what the influential cultural historian Warren Susman called a Culture of Character to a Culture of Personality - and opened up a Pandora's Box of personal anxieties from which we would never quite recover.

The New Groupthink did not arise at one precise moment. Cooperative learning, corporate teamwork, and open office plans emerged at different times and for different reasons. But the mighty force that pulled these trends together was the rise of the World Wide Web, which lent both cool and gravitas to the idea of collaboration. On the Internet, wondrous creations were produced via shared brainpower: Linux, the open-source operating system; Wikipedia, the online encyclopedia; MoveOn.org, the grassroots political movement. These collective productions, exponentially greater than the sum of its parts, were so awe-inspiring that we came to revere the hive mind, the wisdom of crowds, the miracle of crowdsourcing. Collaboration became a sacred concept - the key multiplier for success.
But then we took things a step further than the facts called for. We came to value transparency and to knock down walls - not only online but also in person. We failed to realize that what makes sense for the asynchronous, relatively anonymous interactions of the Internet might not work as well inside the face-to-face, politically charged, acoustically noisy confines of an open-plan office. Instead of distinguishing between online and in-person interaction, we used the lessons of one to inform our thinking about the other.

Sometimes they picked the right answer despite their peers' influence. And Berns and his team found something very interesting about these moments. They were linked to heightened activation in the amygdala, a small organ in the brain associated with upsetting emotions such as the fear of rejection.
Berns refers to this as "the pain of independence," and it has serious implications. Many of our most important civic institutions, from elections to jury trials to the very idea of majority rule, depend on dissenting voices. But when the group is literally capable of changing our perceptions, and when to stand alone is to activate primitive, powerful, and unconscious feelings of rejection, then the health of these institutions seems far more vulnerable than we think.

Of course, the Extrovert Ideal is not a modern invention. Extroversion is in our DNA - literally, according to some psychologists. The trait has been found to be less prevalent in Asia and Africa than in Europe and America, whose populations descend largely from the migrants of the world. It makes sense, say these researchers, that world travelers were more extroverted than those who stayed home - and that they passed on their traits to their children and their children's children. "As personality traits are genetically transmitted," writes the psychologist Kenneth Olson, "each succeeding wave of emigrants to a new continent would give rise over time to a population of more engaged individuals than reside in the emigrants' continent of origin."

If we assume that quiet and loud people have roughly the same number of good (and bad) ideas, then we should worry if the louder and more forceful people always carry the day. This would mean that an awful lot of bad ideas prevail while good ones get squashed. Yet studies in group dynamics suggest that this is exactly what happens. We perceive talkers as smarter than quiet types - even though grade-point averages and SAT and intelligence test scores reveal this perception to be inaccurate. In one experiment in which two strangers met over the phone, those who spoke more were considered more intelligent, better looking, and more likable. We also see talkers as leaders. The more a person talks, the more other group members direct their attention to him, which means that he becomes increasingly powerful as a meeting goes on. It also helps to speak fast; we rate quick talkers as more capable and appealing than slow talkers.
All of this would be fine if more talking were correlated with greater insight, but research suggests that there's no such link. In one study, groups of college students were asked to dolve math problems together and then to rate one another's intelligence and judgment. The students who spoke first and most often were consistently given the highest ratings, even though their suggestions (and math SAT scores) were no better than those of the less talkative students. These same students were given similarly high ratings for their creativity and analytical powers during a separate exercise to develop a business strategy for a start-up company.

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 thrashes 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.