Our lives are shaped as profoundly by personality as by gender or race. And the single most important aspect of personality – the “north and south of temperament,” as one scientist puts it – is where we fall on the introvert-extrovert spectrum. Our place on this continuum influences our choice of friends and mates, and how we make conversation, resolve differences, and show love. It affects the careers we choose and whether or not we succeed at them. It governs how likely we are to exercise, commit adultery, function well without sleep, learn from our mistakes, place big bets in the stock market, delay gratification, be a good leader, and ask “what if.” It’s reflected in our brain pathways, neurotransmitters, and remote corners of our nervous systems. Today introversion and extroversion are two of the most exhaustively researched subjects in personality psychology, arousing the curiosity of hundreds of scientists.

These researchers have made exciting discoveries aided by the latest technology, but they’re part of a long and storied tradition. Poets and philosophers have been thinking about introverts and extroverts since the dawn of recorded time. Both personality types appear in the Bible and in the writings of Greek and Roman physicians, and some evolutionary psychologists say that the history of these types reaches back even farther than that: the animal kingdom also boasts “introverts” and “extroverts,” as we’ll see, from fruit flies to pumpkinseed fish to rhesus monkeys. As with other complementary pairings – masculinity and femininity, East and West, liberal and conservative – humanity would be unrecognizable, and vastly diminished, without both personality styles.

We would all be better off if, before accepting a new job, we evaluated the presence or absence of restorative niches as carefully as we consider the family leave policy or health insurance plans. Introverts should ask themselves: Will this job allow me to spend time on in-character activities like, for example, reading, strategizing, writing, and researching? Will I have a private workspace or be subject to the constant demands of an open office plan? If the job doesn’t give me enough restorative niches, will I have enough free time on evenings and weekends to grant them to myself?

Extroverts will want to look for restorative niches, too. Does the job involve talking, traveling, and meeting new people? Is the office space stimulating enough? If the job isn’t a perfect fit, are the hours flexible enough that I can blow off steam after work? Think through the job description carefully. One highly extroverted woman I interviewed was excited about a position as the “community organizer” for a parenting website, until she realized that she’d be sitting by herself behind a computer every day from nine to five.

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.

The secret to life is to put yourself in the right lighting. For some it’s a Broadway spotlight; for others, a lamplit desk. Use your natural powers – of persistence, concentration, insight, and sensitivity – to do work you love and work that matters. Solve problems, make art, think deeply.

Figure out what you are meant to contribute to the world and make sure you contribute it. If this requires public speaking or networking or other activities that make you uncomfortable, do them anyway. But accept that they’re difficult, get the training you need to make them easier, and reward yourself when you’re done.