Another study, of 38,000 knowledge workers across different sectors, found that the simple act of being interrupted is one of the biggest barriers to productivity. Even multitasking, that prized feat of modern-day office warriors, turns out to be a myth.

Introverts are capable of acting like extroverts for the sake of work they consider important, people they love, or anything they value highly.

What if you love knowledge for its own sake, not necessarily as a blueprint to action? What if you wish there were more, not fewer reflective types in the world?

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 sizeable 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.

Eleanor Roosevelt, Rosa Parks, Gandhi — all these peopled described themselves as quiet and soft-spoken and even shy. And they all took the spotlight, even though every bone in their bodies was telling them not to.

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. Or maybe there's another word for such people: thinkers.

Whoever you are, bear in mind that appearance is not reality. Some people act like extroverts, but the effort costs them energy, authenticity, and even physical health. Others seem aloof or self-contained, but their inner landscapes are rich and full of drama. So the next time you see a person with a composed face and a soft voice, remember that inside her mind she might be solving an equation, composing a sonnet, designing a hat. She might, that is, be deploying the powers of quiet.