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.”

—  Susan Cain, Quiet: The Power of Introverts in a World That Can’t Stop Talking, 168.