Can You Smile Your Way to Success?

They found that asking a participant to recall the happiest time in his or her life resulted in a higher level of abstract thinking than recalling a sad period. Even a happy face preceding a statement helped the participants focus on the big picture.

"Of course, this is a temporary level, and it might die out after some time," but it works for a little while, Labroo said.

The study is consistent with a lot of other research indicating that happiness can have a significant effect on everything from decision-making to blood pressure.

A review of 225 studies, involving 275,000 people, published in the Psychological Bulletin three years ago concluded that happy individuals are more likely to tackle new goals than unhappy people.

"Chronically happy people are, in general, more successful across many life domains than less happy people, and their happiness is, in large part, a consequence of their positive emotions, rather than vice versa," according to that study.

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"Our review provides strong support that happiness, in many cases, leads to successful outcomes, rather than merely following from them," author Sonja Lyubomirsky of the University of California, Riverside, said in releasing that study.

A number of studies have linked happiness with good health, although it is less clear which comes first there. Health is one issue that can have a major impact on personal happiness, but many people seem happy even when confronted with a crippling or life-threatening disease. How can that be?

Some studies insist that happiness is largely independent of our status in life. Australian psychologists studied 900 twin pairs and said earlier this year that they had identified common genes that resulted in distinct personality traits and a predisposition for happiness. Thus, happiness has its roots in our genes, if this study is right, although the various predicaments we find ourselves in can also contribute significantly. It's hard to keep smiling if you're broke, lonely and sick, for example, even if you have the right genes.