Seeing a partially filled glass of water as half full, not half empty, puts you in good stead for living to age 85 or beyond. The most optimistic people live longer than the least optimistic – 15 percent longer for women, 11 percent longer for men, according to a study of 71,173 people published in the Proceedings of the National Academy of Sciences.

The researchers found that the most optimistic people were 50 percent to 70 percent more likely to reach age 85 or older, which they called “exceptional longevity.” Though genetics has been shown to have an effect on life span, the researchers wrote that “emerging evidence suggests nongenetic factors also contribute,” optimism among them.

The study did not determine why optimists lived longer, but experts’ theories include that optimists (compared with pessimists) are better able to cope with stress, can more easily regulate their emotions and resulting behaviors, have healthier lifestyles (including being less likely to smoke or drink alcohol excessively), are more physically active and have more friends and supportive networks.

Sometimes called positive thinkers, optimists expect good things to happen and believe they have some control over outcomes. To be more positive – a trait the researchers say “can be learned” – common advice includes thinking about things you can be grateful for, doing one nice thing a day for someone else, socializing with positive people, being physically active, spending time outdoors and smiling more.