But a growing body of evidence casts the aging of the human brain in a different light. And for anyone planning on growing old, it’s great news.

“There’s not just a straightforward decline in memory as most people believe,” says Laura Carstensen, PhD, a psychology professor and director of the Stanford Center on Longevity. “There are more positive changes as well.”

The news is that older people tend to be happier. While they might not remember names as well as younger people, new research into cognitive functioning shows an uncanny ability to focus on the positive in life.

“Human minds don’t process information like a computer,” says Carstensen, who was one of the first researchers to discover that older people tend to be happier. “We process what is relevant to our goals.”

And as we age, our goals tend to change — toward achieving emotional well-being, she says.

Carstensen’s research into the “socioemotional selectivity theory,” aka “the positivity effect,” has created a new field of neuroscience research. “It has had a huge impact in psychology in fields as diverse as the neuroscience of aging to personality and social relationships,” says Stacey Wood, PhD, a neuropsychologist and associate professor of psychology at Scripps College, who regularly preaches the positivity effect in lectures to clinical audiences. “We used to believe that as they aged, older adults became disengaged, their emotions became dampened. This is no longer true. There’s really been a paradigm shift due to Carstensen’s work.”

The studies

The concept of the positivity effect first began with a surprise finding in Carstensen’s lab back in 2003. She was studying the memories of young and old people by showing them a series of positive and negative images and asking them to note which photos they could remember.

“We used a set of photos widely used by researchers interested in eliciting emotion,” says Mara Mather, PhD, a former postdoctoral researcher in Carstensen’s lab, now on the University of Southern California faculty. The shots ranged from a duck stuck in an oil spill to an adult hugging happy kids. The older adults recalled fewer of the photos in general, which wasn’t surprising. What was surprising was that they remembered far more of the positive photos than the younger subjects.

The lab has since replicated these results in a series of experiments. One study involving 300 nuns showed that, as they aged, the nuns remembered their past in a more positive light right down to the number of headaches they suffered. The study compared the nuns’ answers to a questionnaire in 1987 with their answers in 2001. They were asked to remember such things as levels of depression or amount of time they spent doing healthy activities, such as walking or eating healthily.

Another study, which involved adults viewing faces with various expressions, found that older adults spent more time viewing the positive, smiling faces than the sad or angry faces.

Just why this surprising preference for the positive was happening among the older population suddenly became a matter for debate. What was the cause? Was it biological or motivational?

“We thought maybe there was some sort of depletion in the brain,” Carstensen says. “We’ve since ruled this out. We believe it’s motivational.”

Why the glass is half full

A follow-up study by Mather sat participants in front of a series of positive and negative photos while wearing headphones and listening to different sounds. When asked to do two things at once — listen to the headphones while trying to remember the photos — the positivity effect disappeared.

“If this was an automatic effect, the distraction shouldn’t have mattered,” Mather says. “But it did matter. The effect was reversed, which indicates it’s intentional.”

Further studies that showed a similar positivity effect in young people whose expected life spans were cut short by cancer or AIDS led to Carstensen’s current “shorter life span” explanation for the positivity effect.

“As older people realize they have less time available, they change their goals,” Carstensen says. “They’re more concerned about short-term emotional well-being. They put more importance on relationships. Younger people put how they feel on hold in order to reach long-term goals.”

But how does all this positivity square with that cultural icon, the grumpy old coot? Well, it doesn’t.

“The rates of depression among older adults actually decline,” Wood says. “Therapists are now aware that it isn’t normal for an older person to be disengaged or depressed and will treat them as such.”

But the misconception still persists among the general public, she says.

“I get people all the time who say, ‘Geez, you haven’t met my grandfather.’ I explain that this phenomenon doesn’t mean that someone who always looked on the negative side of life will suddenly be wearing rose-colored glasses. It’s just that they may have mellowed a bit.”

And there might be some minor negative effects from the positivity effect that researchers are beginning to explore. Older adults do seem to have some particular vulnerabilities to fraud that could be caused, in part, by missing certain red flags because they’re focusing too much on the positive, Wood says.

Still in general, the positivity effect is, well, positive.

“When I lecture undergrads about the positivity effect, I look out in the audience and see them smile,” says Carstensen. “I tell them, ‘This is the worst time in your life, not the best like everyone tells you. The best is yet to come.’”