While parental love can bolster self-esteem for some, there's no direct line between childhood experiences and adult self-image. Ugly ducklings sometimes turn into swans—or find their looks suddenly validated by committee. Donelle Ruwe, now an English professor at Northern Arizona University, grew up terribly gawky, a teen with glasses, a back brace and, yes, even headgear. But she played piano very well. At the age of 19, she'd recently shed the brace, and a pageant scout looking to improve the talent quotient in a beauty competition suggested she sign up. She did, and was crowned Miss Meridian, Iowa, of 1985.

"For the first time, I felt that I was attractive," she says. That new confidence in her looks actually made her feel freer to develop her intellect—she was quicker to assert her opinions in class and debate with others. "I think that when you are self-conscious about your body, too much of your mind and emotions are focused on it," she says. "But once you let go of that self-consciousness, you can interact without it getting in the way."

But those who are gorgeous from the get-go face their own set of potential problems. Very attractive kids may grow up to be insecure adults, especially if they were praised solely for their appearance. They may develop a particularly harsh way of assessing themselves—what Heather Patrick, a researcher at Baylor College of Medicine, calls "contingent self-esteem." They may feel good about their looks only if they meet a specific, and usually very high, expectation, such as weighing in at a certain number. Self-satisfaction is not on a spectrum for such people: If they don't meet their standard, they feel absolutely ugly.

Carol Alt, the former Sports Illustrated cover girl, fell victim to this phenomenon in 1995, when a fashion photographer declared her too jiggly for her bikini. After he spent a day on location attempting to hide her extra ounces of flesh behind rocks, he fired her and sent her back to Los Angeles, where she slipped into a weeks-long, Nyquil-soaked depression. "I'd feel fat and guilty anytime I ate," she says now. "I didn't feel I had control over my body, and that fragility was frustrating and even terrifying."

With looks, as in other domains of life, we relish recognition more and recover better from failure when we believe that good results come from effort and not just from what God gave us. If you are born lovely, you have only your parents' genetic contributions to thank. But if you become more attractive because you've invested energy in taking good care of yourself, the credit is all yours.

Alt says she feels better-looking now, at 45, than she ever has. The author of Eating in the Raw says that overhauling her diet made the difference. "Now I'm more complimented when someone comments on something I've worked for, such as keeping myself healthy, than when someone says, 'You're beautiful.' "