Having a positive outlook on life could be the key to living a long life.
Recent research has found that happier people tend to live to 100, while those who have a sour view on life have a far shorter lifespan.
Scientists think that happier people might have their better attitude genetically ingrained in them.
Basing their study on Ashkenazi Jews from eastern Europe, researchers found that they were more conscientious and less neurotic than the average sample taken from a general population score.
The Ashkenazi population has remained relatively genetically pure and therefore their genetics are easier to study in comparison to a broader genetic group.
The researchers interviewed 243 people near the age of 100.
Nir Barzilai, who works at the Albert Einstein College of Medicine's Institute for Aging Research, New York, discovered that this group valued a good laugh very highly and also chose to express their emotions, rather than bottle things up.
While there is some evidence to show that personality traits can change between the ages of 70 and 100, the results of the study showed a strong correlation between a sunny disposition and long life.
"Our findings suggest that centenarians share particular personality traits and that genetically based aspects of personality may play an important role in achieving both good health and exceptional longevity," wrote Barzilai.