Why do some people live to be older than others? You know the standard explanations: keeping an abstemious diet; engaging in regular exercise; and, if you're an unusual Frenchwoman, smoking cigarettes until you are 117 years old.

But what effect does your personality have on your longevity? Do some kinds of temperaments lead to longer lives? A new study in the Journal of the American Geriatrics Society looked at this question by examining the personality traits of 246 children of people who had lived to be at least 100. (The study chose the offspring of centenarians because they are easier to follow over time than the very aged since they don't die as often before follow-up interviews can be conducted. Also, children of those who live to 100 are themselves likelier to live longer.)

The study shows that those who live the longest are more outgoing, more active and less neurotic than other people. Long-living women are also more likely to be empathetic and cooperative than women with a normal life span. These findings comport with what you would expect from evolutionary theory: those who are extroverted enough to make friends and help others are those who are going to be able to gather enough resources to make it through tough times. (The Key To Success May Be Happiness.)

Interestingly, however, other traits that you might consider advantageous had no impact in this study on whether participants were likely to live longer. Those who were more self-disciplined, for instance, were no more likely to live to be very old (which might explain the long life of the smoking French lady). Also, being open to new ideas had no relationship to long life, which might explain all those cantankerous old people who are fixed in their ways.

Whether you can successfully change your personality as an adult is the subject of a longstanding psychological debate (here's a pdf of one paper that lays out the issues). But the new paper suggests that if you want long life, you should strive to be as outgoing as possible.

Unfortunately, another recent study shows that your mother's personality - which, of course, you can't change - may also help determine your longevity. That study looked at nearly 28,000 Norwegian mothers and found that those moms who were more anxious, depressed and angry were more likely to feed their kids unhealthy diets full of chocolate, soda and pancakes. Patterns of childhood eating can be very hard to break when we're adults adults, which may mean that kids of depressed moms end up dying younger.

Personality isn't destiny, of course, and everyone knows that individuals (and perhaps entire nations) can learn to change. But both of the new studies show that long life isn't just a matter of your physical health but of your mental health also.