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Secret to old age: Happy nuns live longer according to research from the University of Kentucky - but why is that, and what can we learn to benefit from it?

Happiness has a positive influence on longevity and health, but what's behind this effect? Psychologists are uncovering evidence that positive emotions undo the physical damage done by stress, fear and anxiety.

Three generations ago, 180 young women wrote brief essays describing why they wanted to become nuns. Years later, a team of psychological researchers came across these spiritual autobiographies in the convent's archives.

The researchers were seeking material that would confirm earlier studies hinting at a link between having a good vocabulary in youth and a low risk of Alzheimer's disease in old age. What they found was something even more amazing.

Although the young women had barely been out of college when they wrote their "why I want to be a nun" essays, the emotions expressed in these youthful writings were predictive of how long they would live: those who wrote the most upbeat autobiographies lived more than 10 years longer than those whose language was more neutral.

The results were particularly striking because all members of the convent lived similar lifestyles, eliminating many of the variables that normally make it difficult to interpret longevity studies.

"Once in a lifetime finding"

"It was a phenomenal finding," says Deborah Danner, a psychologist at the University of Kentucky in the U.S., who spearheaded the study. "A researcher gets a finding like that maybe once in a lifetime."

Because the autobiographies were written with the knowledge that they would be read by the mother superior, none were negative. "But even with that, you could get a feel for the person," says Danner. "Some had this glow about them."

Danner's study, however, offered no clues as to why positive emotions might have such strong life-extending effects.

Barbara Fredrickson, an associate professor of psychology at the University of Michigan, believes that part of the answer is something she calls the "undo effect." According to this theory, positive emotions help you live longer by shutting down the health-damaging side effects of negative ones.

Fredrickson's theory begins with the observation that negative emotions, like fear and anxiety, helped our ancestors survive by enhancing the flight-or-fight response to very real threats, such as predators or raiders from an enemy tribe. Even disgust plays a survival role, encouraging you to spit out food whose repulsive taste might mean that it is poisonous or spoiled.

Lingering cardiovascular effects

But when the crisis is gone, negative emotions produce lingering effects. One of these is excessive "cardiovascular reactivity."

Cardiovascular reactivity is a laboratory measure of cardiac excitability. "It's kind of like being jumpy," says Brooks Gump, an associate professor of psychology and stress researcher at the State University of New York in Oswego. Behaviourally, he says, it is related to excessive "vigilance," which is the state of being constantly on guard for potential dangers.

Not only is it physically draining to live in a perpetual state of high vigilance, but high cardiovascular reactivity has been linked to increased risk of heart attack.

Fredrickson believes that positive emotions work their magic by producing a rapid unwinding of pent-up tension, rapidly restoring the cardiovascular system to normal. People who quickly bounce back from stress often speed the process by deliberately harnessing such emotions as amusement, interest, excitement, and happiness, she says.

To test her theory, Fredrickson and co-worker Michele Tugade, now of Vassar College in Poughkeepsie, New York, told a group of student volunteers that they had only a few minutes to prepare a speech that would be critiqued by experts.

After letting the students get nervous about that for a few minutes, Fredrickson and Tugade then let them off the hook by telling them they wouldn't actually have to deliver their speeches. All the while, they monitored heart rates, blood pressures, and other factors related to cardiovascular reactivity. Afterward, they asked the students to report how they'd felt during the experiment.

Not surprisingly, everyone got nervous about the speech. But those who viewed the experiment with amusement, interest, and good-humoured excitement saw their heart rates return to normal much more quickly than those who were angry about being fooled.

Bouncing back

In a second experiment, Fredrickson and Tugade first gave a group of students a battery of questions designed to measure how well they normally handled stress. Next, these students were given the speech-preparation task, then - as with the first group - were told that they wouldn't actually be delivering their speeches. In an article published in the Journal of Personality and Social Psychology, Tugade and Fredrickson reported that even those who normally were slow to bounce back could be coached to recover more quickly by being told to view the experiment as a challenge, rather than a threat.

The 'undo effect', however, doesn't explain why our distant ancestors needed positive emotions. After all, very few people in primitive societies lived long enough to die of heart attacks, no matter how badly they abused their cardiovascular systems. Also, positive emotions often occur in situations where there are no negative emotions to undo. If these carried any survival value at all, it must have involved something other than the "undo" effect.

For years, anthropologists and evolutionary psychologists have argued that this 'something' was related to family bonding - valuable because it would have facilitated the survival of the most tightly knit clans. But while that might explain emotions like love, Fredrickson says, it does nothing to explain other positive emotions, such as joy, playfulness, and humour.

Flexible and creative

Fredrickson believes that a critical clue lies in psychological studies demonstrating that positive emotions make people more flexible and creative than do negative or neutral feelings.

Negative emotions, she says, give us a heightened sense of detail that makes us hypersensitive to minute clues related to the source of a threat. But that hypersensitivity also produces a form of tunnel vision in which we ignore anything unrelated to the danger. Many people experience something similar in automobile accidents: they can recall the tiniest details of the accident, but have only vague recollections of whatever else was going on at the time. Or, Fredrickson's preferred example is the mugging victim might be able to describe the gun in detail but has no idea what kind of clothes the mugger was wearing.

Fredrickson speculated that just as positive emotions can undo the cardiovascular effects of negative ones, they may also reverse the attention-narrowing effects of negative feelings: broadening our perspectives, rather than limiting them.

To verify this, she assembled another group of students and showed them film clips. Some saw frightening clips, some saw humorous ones, anger-inducing ones, or peaceful ones. Then she gave them a matching test in which they were shown a simple drawing and asked which of two other drawings it most resembled. The drawings were designed so that people tend to give one answer if they focus on the details, and another answer if they focus on the big picture.

The results, published in the journal Cognition and Emotion, confirmed Fredrickson's suspicion that positive emotions indeed affect our perceptions. Students who had seen the humorous or peaceful clips were more likely to match objects according to gestalt impressions.

In a variation on the same experiment, the students were also asked to contemplate the emotion generated by the film clip and to jot down a list of "things you would like to do, right now."

Those who saw the pleasant film clips averaged 14 activities on their lists, compared to nine activities for those who saw the more disturbing clips. Students who saw an abstract, emotionally neutral clip of computer-generated sticks assembling themselves into a pile split the difference, listing an average of about 11 activities that they would like to do.

Building resources

All of this fits perfectly with the role that positive emotions might have played in pre-human tribes, Fredrickson says. The focusing effect of negative emotions was important for surviving in life-or-death situations, but the ability to feel happiness, joy, and humour were of long-term value because they opened the mind to new ideas. "The more you do that, the more tools you have in the tool bag the next time you face threats," she says. "The emotions are transient, but the resources are durable. If you build a friendship through being playful, that friendship is a lasting resource."

On an individual level, Fredrickson's theory also says that taking times to do things that make you feel happy isn't simply self-indulgent frivolity, she says. Not only are joy and playfulness good for the heart, but they're also good for society. "That opens up a different window on the value off positive emotions," Fredrickson says.

Other researchers are intrigued by Fredrickson's findings. Susan Folkman, a professor of medicine at the University of California in San Francisco, has spent two decades studying how people cope with long-term stresses such as bereavement or caring for a chronically ill child.

Contrary to one might expect, she says, these people frequently experience positive emotions. "These emotions aren't there by accident," she adds. "Mother Nature doesn't work that way. I think that they give a person time out from the intense stress to restore their resources and keep going. This is very consistent with Barbara [Fredrickson]'s work."