Young adults are most likely to recall and fixate on unpleasant events, while older people focus on the positives, an approach that might be programmed into their brains, suggest studies coming out Sunday.

This age-linked, selective memory could help explain a growing pool of evidence that older adults are often more content than their kids or grandkids, who are at higher risk for serious depression.

"It's as though older people are saying, 'Don't sweat the small stuff' because they realize life is short, and they don't want to spend their time looking at the bad things," said psychologist Susan Turk Charles of the University of California-Irvine. She and co-author Laura Carstensen report on their studies with 208 adults, 18 to 86 years old, in the journal Experimental Psychology: General.

Study participants looked at negative, positive and neutral images on a computer. For example, one negative photo showed sad people leaving a plane crash; some positive images featured families enjoying the beauty in nature.

Afterward, everyone was asked to describe as many images as they could recall. Then researchers showed images and asked whether these were among shots participants had viewed before.

Adults in their 60s and older tended to remember about as many pleasant events as younger people. But the younger their age, the more likely adults were to recall unhappy images.

Young adults might need antennae for ugly or threatening aspects of life as they jockey to establish careers and find partners, Charles said. As adults age, they put more value on emotional meaning in life, often through deep intimacy and peace of mind. Selective memory for positive events might further these goals, she said.

In another study using brain scans, young and older adults who saw pleasant images showed equal activation of the amygdala region of their brains, a key emotional center linked to memory areas. But negative images triggered more activation in young people.

"This could reflect brain changes with aging or mean that pursuing different goals changes the brain," said psychologist Mara Mather of the University of California at Santa Cruz, who did the brain scans.

Shrugging off the nasty aspects of life is good for mental health, but it might have a down side, Charles said. Researchers are studying if older people's rosy outlook could lead them to overlook the pitfalls in important documents, such as health insurance policies.

"No doubt there are some grumpy old men," added Robert Butler, president and CEO of the International Longevity Center-USA, a New York think tank. But research and experience refute the popular view that most older people are miserable whiners, Butler said.