If you were to guess how long your best friend would live, how accurate do you think you'd be?
Chances are you'd be pretty on-point, at least according to a new study from a team of psychologists and medical researchers.
As it turns out, decades of research have linked specific personality traits — from conscientiousness to extroversion — to a longer life expectancy.
And close friends are surprisingly good at identifying these characteristics.
For their paper, the researchers used data from a 75-year study of 600 people (300 engaged couples) who began taking part in the study between 1935 and 1938 (when they were in their mid-20s) and continued participating until 2013.
When they joined the study in the 1930s, each participant picked three to eight close eight friends to rate their personality using a 36-question scale created by psychologist E. Lowell Kelly in 1940. To make sure the scale was still an accurate measure of personality types, the researchers compared it with several other personality tests created by psychologists within the past decade.
Questions in the scale ranged from general queries like "Is he physically energetic and peppy?"to more personal questions like "How does he meet his appointments?" and "Is he nervous and 'flies off the handle' easily?"
Using the questionnaire, the researchers ended up with four key traits that emerged as key measures of longevity — two for women and two for men. Of the men in the study, those who were seen by their friends as more conscientious (meaning they were less likely to take risks and also tended to be more thorough and efficient) and open (to new and different ideas, feelings, and concepts) lived longer. Of the women, those who were seen as more emotionally stable and agreeable (or friendly) lived longer.
While the study's gender differences likely reflect the time period in which the original research began, the findings are still significant. People who are more conscientious (regardless of their gender) are less likely to do things that put their lives at risk, like driving under the influence or speeding, and more likely to pay attention to their health by doing things like exercising and taking time to relax.
The research squares with previous research on aging and personality, which has linked several of the same traits — some of which may be genetic — with longer life.
A 2007 study, for example, followed 1,253 men and women from California between 1930 and 2000 found that people (regardless of their gender) who were conscientious as children and as adults lived longer than their peers who were not conscientious during either phase of their lives. This trait — more than any of the other characteristics the researchers studied — was found to be a strong predictor of life expectancy.
Another more recent study of 243 people between the ages of 95 and 100 (75% of whom were women) found that all of them were, on average, not only more conscientious than the average person but more optimistic, easy-going, and extroverted as well.
That study's participants also tended to laugh frequently and express their emotions openly with one another (as opposed to bottling them up). Since that study looked only at people who'd already made it into ripe old age, however, it's impossible to say whether or not the study participants developed these characteristics as a result of old age or if the traits helped them to live as long as they had.
