Older people tend to be happier. But why? Some psychologists believe that cognitive processes are responsible - in particular, focusing on and remembering positive events and leaving behind negative ones; those processes, they think, help older people regulate their emotions, letting them view life in a sunnier light. "There is a lot of good theory about this age difference in happiness," says psychologist Derek M. Isaacowitz of Northeastern University, "but much of the research does not provide direct evidence" of the links between such phenomena and actual happiness. In a new article in Perspectives on Psychological Science, a journal published by the Association for Psychological Science, Isaacowitz and the late Fredda Blanchard-Fields of Georgia Institute of Technology argue for more rigorous research.

Researchers, including the authors, have found that older people shown pictures of faces or situations tend to focus on and remember the happier ones more and the negative ones less. Other studies have discovered that as people age, they seek out situations that will lift their moods - for instance, pruning social circles of friends or acquaintances who might bring them down. Still other work finds that older adults learn to let go of loss and disappointment over unachieved goals, and hew their goals toward greater wellbeing.

What's missing, say the authors, are consistently demonstrated direct links between these strategies and phenomena and changes of mood for the better. One reason, Isaacowitz suggests, is that lab tests yield results that are not straightforward. "When we try to use those cognitive processes to predict change of mood, they don't always do so," he explains. "Sometimes looking at positive pictures doesn't make people feel better." A closer review of the literature also reveals contradictions. Some people - younger ones, for instance - may make themselves feel better by accentuating the negative in others' situations or characteristics. And whereas some psychologists find that high scores on certain cognitive tests correlate in older people with the ability to keep their spirits up, other researchers hypothesize that happiness in later life is an effect of cognitive losses - which force older people to concentrate on simpler, happier thoughts.

More rigorous methods probably won't overthrow the current theories, says Isaacowitz, but they will complicate the picture. "It won't be as easy to say old people are happier. But even if they are happier on average, we still want to know in what situations does this particular strategy make this particular person with these particular qualities or strengths feel good."