(Finland is a famously introverted nation. Finnish joke: How can you tell if a Finn likes you? He's staring at your shoes instead of his own.)

I'm continually amazed by how many people who appear to be extroverts are actually introverts.

In the first study, Grant and his colleagues analyzed data from one of the five biggest pizza chains in the United States. They discovered that the weekly profits of the stores managed by extroverts were 16 percent higher than the profits of those led by introverts—but only when the employees were passive types who tended to do their job without exercising initiative. Introverted leaders had the exact opposite results. When they worked with employees who actively tried to improve work procedures, their stores outperformed those led by extroverts by more than 14 percent.

Love is essential, gregariousness is optional.

Even when the attention focused on me is positive, I am uncomfortable being looked at by a lot of people - it's just not my natural state of being.

Love is essential; gregariousness is optional. Cherish your nearest and dearest. Work with colleagues you like and respect. Scan new acquaintances for those who might fall into the former categories or whose company you enjoy for its own sake. And don't worry about socializing with everyone else. Relationships make everyone happier, introverts included, but think quality over quantity.

(Finland is a famously introverted nation. Finnish joke: How can you tell if a Finn likes you? He's staring at your shoes instead of his own.)