The average life expectancy in the U.S. is 78.5 years -- and by now we all know that certain healthy behaviors might help to extend that figure, whether it's exercise, nutrition, or little everyday habits, like cooking more meals at home.

But could your personality affect how many birthdays you celebrate? Maybe so, according to a body of research evaluating the role our outlooks can play in life span.

Of course, it's important to remember that many factors, from genetics to lifestyle, work together to determine life expectancy -- but researchers have found that these six personality traits, in particular, are more common in those who lead longer lives. Click through, then let us know what you think. Do you have any of the six?

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  • Conscientious

    In their 2012 book "<a href="http://www.amazon.com/Longevity-Project-Surprising-Discoveries-Eight-Decade/dp/0452297702" target="_hplink">The Longevity Project</a>," which looked at research over the course of 80 years, authors Howard S. Friedman and Leslie R. Martin identified an association between being conscientious and a longer life span. "Conscientiousness, which was the best predictor of longevity when measured in childhood, also turned out to be the best personality predictor of long life when measured in adulthood," <a href="http://www.amazon.com/Longevity-Project-Surprising-Discoveries-Eight-Decade/dp/0452297702" target="_hplink">the authors wrote in their book</a>. "The young adults who were thrifty, persistent, detail oriented, and responsible lived the longest." Why do more prudent people tend to live longer? According to the authors, this group is more likely to take care of their health and avoid risks, and they also develop healthier relationships, whether it be romantic, friendly or work-related. "That's right, conscientious people create healthy, long-life pathways for themselves," Friedman and Martin wrote. And finally, the researchers point out that some people seem to have a biological predisposition toward a more careful personality. "While we are not yet sure of the precise physiological reasons," they write, "it appears that conscientious and un- conscientious people have different levels of certain chemicals in their brains, including serotonin." For more on the phenomenon, and other insights into longevity, <a href="http://www.amazon.com/Longevity-Project-Surprising-Discoveries-Eight-Decade/dp/0452297702" target="_hplink">check out "The Longevity Project" here</a>.

  • Easy To Laugh

    In a study published this past May in the journal <em>Aging</em>, researchers from Albert Einstein College of Medicine and Yeshiva University pinpointed several personality traits linked to a longer lifespan. Among the list? Frequent laughter, <a href="http://www.huffingtonpost.com/2012/05/29/optimism-longer-life-longevity-genes-personality_n_1553967.html" target="_hplink">HuffPost reported when the findings were released</a>. "When I started working with centenarians, I thought we'd find that they survived so long in part because they were mean and ornery," study researcher Dr. Nir Barzilai, M.D., director of Einstein's Institute for Aging Research, <a href="http://www.eurekalert.org/pub_releases/2012-05/aeco-gm052412.php" target="_hplink">said in a statement</a>. "But when we assessed the personalities of these 243 centenarians, we found qualities that clearly reflect a positive attitude towards life."

  • Socially Connected

    Thank your family and friends for this one: a 2010 study published in the journal <em>PloS Medicine</em> found that <a href="http://www.plosmedicine.org/article/info%3Adoi%2F10.1371%2Fjournal.pmed.1000316" target="_hplink">strong social relationships</a> can boost survival odds by 50 percent. The Brigham Young University and University of North Carolina at Chapel Hill researchers evaluated 148 studies. "We take relationships for granted as humans -- we're like fish that don't notice the water," BYU's Timothy Smith <a href="http://www.sciencedaily.com/releases/2010/07/100727174909.htm" target="_hplink">said in a statement about the findings</a>. "That constant interaction is not only beneficial psychologically but directly to our physical health."

  • Optimistic

    The same 2012 <em>Aging</em> study that identified frequent laughter as a boost to longevity also found that optimism might tack on years to your life. Out of the 243 centenarians evaluated in the research, most were optimistic and easygoing, study researcher Dr. Nir Barzilai, M.D., director of Einstein's Institute for Aging Research, <a href="http://www.eurekalert.org/pub_releases/2012-05/aeco-gm052412.php" target="_hplink">said in a statement</a>. "Some evidence indicates that personality can change between the ages of 70 and 100, so we don't know whether our centenarians have maintained their personality traits across their entire lifespans," <a href="http://www.eurekalert.org/pub_releases/2012-05/aeco-gm052412.php" target="_hplink">he said in the release</a>. "Nevertheless, 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."

  • Happy

    Don't worry, be happy, live longer? A study published last year in the journal <em>Proceedings of the National Academy of Sciences</em> found that older people who report being happy have a 35 percent decreased risk of dying over five years, <a href="http://www.huffingtonpost.com/2011/11/01/happiness-long-life-_n_1068209.html" target="_hplink">HuffPost reported when the findings were released</a>. The researchers evaluated more than 3,000 people by monitoring their happiness throughout the day -- they then followed up five years later to see how many had died. "I was a bit surprised that the happiness effect was so strong, even among people who had chronic diseases," study author Andrew Steptoe, a professor at University College, London, <a href="http://vitals.msnbc.msn.com/_news/2011/10/31/8565511-want-to-live-longer-get-happy-study-says?ocid=twitter" target="_hplink">told MSNBC</a>.

  • Extroverted

    <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1532-5415.2009.02189.x/abstract" target="_hplink">A 2009 study published in the <em>Journal of the American Geriatrics Society</em></a> looked at the offspring of centenarians (other research has found <a href="http://www.sciencedaily.com/releases/2009/04/090403114823.htm" target="_hplink">exceptional longevity tends to run in families</a>) -- the volunteers were typically in the high range for extroversion (and in the low range for neuroticism). "It's likely that the low neuroticism and higher extroversion will confer health benefits for these subjects," study author Thomas Perls, M.D., MPH, director of the New England Centenarian Study, <a href="http://www.sciencedaily.com/releases/2009/04/090403114823.htm" target="_hplink">said in a statement </a>when the findings were released. "For example, people who are lower in neuroticism are able to manage or regulate stressful situations more effectively than those with higher neuroticism levels. Similarly, high extroversion levels have been associated with establishing friendships and looking after yourself." The women evaluated in the study also scored high for agreeableness.