It may be that the easiest way to kill happiness is to pursue happiness. A desperate search for happiness will likely put too much emphasis on self, and that could backfire.
Instead, scores of research projects suggest, it's better to put the emphasis on others, which psychologists call prosocial behavior. Concentrate on making someone else happy, and chances are you'll feel pretty good too.
But what does it mean to be happy? Scientists can't even agree on a definition, although they've filled bookcases and professional journals with advice on how to get it.
Do you have to be rich to be happy? No.
Can you be happy if you are poor? Yes, but it may be more difficult.
How about if you're sick, or old, or stuck in a lousy job?
The oddest thing about happiness is some people are happy even in dire circumstances, and others are sour when it seems like they've got it made, suggesting that happiness is in your genes, and it's a key part of your personality. Either you've got it or you don't.
There is evidence that a gene that is associated with happiness in women doesn't work the same for men. Scientists at the National Institutes of Health and several research institutions announced two years ago that women who had the "happiness gene" said they were happier than women without it.
But the same gene is known as the "warrior gene" because it is also associated with aggressiveness and antisocial behavior.
Maybe that explains why women tend to be happier than men, these researchers concluded.
Although there is much disagreement among the experts, there is some consensus on at least one factor: Having others in your life is critical. The biggest foe of happiness may simply be loneliness.
In the latest study, researchers at Stanford University argue that if you can just make someone else smile, you'll be on the right track. They conducted six experiments involving 543 persons of all ages across the country and concluded that making someone smile is as good for the giver as it is for the receiver.
But, they added, if you set out to make someone happy, instead of just smile, you will probably fail. That's because happiness is a vague, abstract condition and in the end you won't know if the other person is really happy, so you will be frustrated and less happy yourself.
Making someone smile is a concrete goal, they said, so it's easier to achieve. In all six experiments, participants who set out to achieve a concrete goal, like making someone else smile, felt they had succeeded, although those who tried to make someone else happy felt like they had fallen short.
"A prosocial act can not only boost the happiness of the recipient, but it can boost the happiness of the giver as well," said psychologist Jennifer Aaker, lead author of that study, published in the Journal of Experimental Psychology.
Aaker and her associates concede in their study that they don't know if that effect lasts very long, although if you can make someone smile all the time, chances are they're happy. But as for yourself, don't think too much about it.
Psychologists led by Yale University concluded three years ago that happiness has a "dark side" because trying too hard to find it can lead to "disappointment and decreased happiness." Just try to make someone smile instead, the Stanford researchers would say.