The secret to happiness, it turns out, may not be wealth or power. Or love or success or faithful friendship. Or Ray Charles crooning ''Georgia on My Mind'' or even chocolate mousse.

Finding happiness may mean going no further than your very own forehead -- the left prefrontal cortex of your brain, to be exact. The more the sparks fly from this sliver of gray matter, the more electrical impulses it generates, the happier you are.

That is the conclusion of Richard J. Davidson, a professor of psychology and psychiatry at the University of Wisconsin at Madison, and others who have examined adults, children, infants, even Rhesus monkeys. Over the last several years, they have tested perky, enthusiastic people and pessimistic, morose ones. The results are always the same. People blessed with effervescent left prefrontal cortices are much more likely to be smiling.

Dr. Davidson is part of a small band of pioneers who have set out over the last decade to discover what many philosophers but few scientific researchers have bothered to ask: What is it, exactly, that makes us happy?

They are marshaling all the most sophisticated scientific techniques: searching for a genetic basis for happiness, brain imaging to pinpoint the spot on the brain where happiness resides, and in-the-field surveys to try to understand which activities or stimuli make people more or less happy. And they are interested in a range of possible applications. How does happiness affect physiological symptoms like stress and heart disease? Can drugs be used effectively to make unhappy people happy? Are our brains coded from birth for a certain level of happiness, or can they be altered by experiences when we are young, or even as adults?

This is revolutionary stuff, not only for biologists but also for psychologists, who have concentrated much of this century on pathology, obsession, melancholy and angst.

''Look in a psychology textbook,'' said Daniel Kahneman, a professor of psychology and public affairs at Princeton University and another happiness sleuth. ''There are a lot of pages devoted to anxiety and depression. Happiness might not even be there.''

Norbert Schwarz, a professor of psychology at the University of Michigan, said it had historically been tough to get grants to study what tickles people's fancy.

''When you're deciding whether to fund research,'' Dr. Schwarz said, ''it seems much more important to say you want to help people not to get depressed than to say you want to help people enjoy their dinner more.''

But these days, happiness research is on the upswing. Chock it up to the Don't Sweat the Small Stuff movement, experts say, or to the emphasis on physical health and ''wellness'' that has people smoking less and Stairmastering more. But even the current president of the American Psychological Association, Martin E. P. Seligman, has been making speeches over the past year urging researchers to study a new ''positive'' psychology.

Happiness, it goes without saying, is highly subjective and some researchers are trying to better define and measure this squishy subject.

Edward F. Diener, a University of Illinois psychologist who conducts happiness research, said in an interview: ''We're trying not to just ask people how happy they are in general, but to document it at specific points. Happiness is how frequently you're happy, not how intensely you're happy. Having some peaks in there is nice -- it's certainly not bad -- but if you have a peak, it could be because you're unhappy and then you had something happen to make you superhappy. Then you have to go back to the normal thing.''

Michael Argyle, a psychologist at Oxford University, has found some common threads. Money, he says, makes little difference to happiness, except for people who are very poor. People on the job are happiest when they have good relationships with co-workers and when part of their day is spent ''wasting time, fooling around, and sharing gossip and jokes,'' he said. And for some reason, watching soap operas on television makes people happy (''I think they've got imaginary friends there,'' he said.)

Increasingly, though, most happiness researchers are convinced that a healthy part of happiness is physiological and genetic.

Tests on twins have found that ''identical twins separated from birth are more similar in how happy they are than fraternal twins who grew up together,'' Dr. Diener said.

The research of Dr. Davidson and others provides some of the most compelling evidence yet.

People who describe themselves as optimistic, engaged, ''the kind of people who jump out of bed in the morning and are ready to tackle the world,'' as he put it, have consistently higher levels of left prefrontal lobe activity. Physiologically, they also have ''higher levels of natural antibody activity -- antigens against everything from colds and flu to cancers.''

By contrast, people who are depressed have greater activity in their right prefrontal lobe. And children with more active right prefrontal lobes show ''excessive wariness in response to unfamiliar situations,'' Dr. Davidson said.

To see whether anticipation of something good or bad makes a difference, Dr. Davidson tested heavy smokers who were deprived of cigarettes for a day and then shown a lighted cigarette and told they would be able to smoke in two minutes. During those two minutes, the smokers showed a strong increase in left prefrontal lobe activity.

On the other hand, a group of people with intense fear of making public speeches were told they would be required to do just that. Their right prefrontal lobes went ballistic as they got closer to making the speech.

Naturally, drug companies have been banging on Dr. Davidson's door. He says that some studies have found that antidepression drugs increase left prefrontal cortex activity, although there is no research yet on how long that effect lasts.

Yet drawing the line between the physical and the psychological is not easy. What is cause and what is effect? Are people with more prefrontal cortex activity happier or do happier people have more prefrontal cortex activity?

Dr. Davidson, for example, is studying whether experiences -- meditation, for example -- can produce changes in prefrontal brain activity ''to more definitively answer the question on nature versus nurture,'' he said. ''Data suggest there's a lot of plasticity that appears to be present up until the time of puberty. But brain function might be malleable even in adults.''

He assisted in a recent study conducted with Jon Kabat-Zinn, a meditation expert at the University of Massachusetts Medical Center in Worcester, in which stressed executives of a high-powered biotechnology company were given an eight-week course in meditation -- one three-hour class a week and an assignment to practice 45 minutes a day. The results are not yet in, Dr. Davidson said.

With the blessing of the Dalai Lama, Dr. Davidson is also studying Buddhist monks, both in Tibet and Wisconsin, to see whether their lives of meditation show up on their prefrontal lobes. ''To get these people to do the research is very difficult,'' he added. ''They tell us if we really want to learn about meditation they could give us instruction, and if we like it we can teach it to other people.''

Whatever this research will ultimately show, happiness is clearly more than the sum of brain circuits. Researchers have noticed, for example, that people's responses to questions about happiness change depending on the context in which they are asked. If asked about their lives on a sunny day, people are likely to express more contentment than on a rainy day.

Dr. Schwarz, a co-editor of ''Well-Being: Foundations of Hedonic Psychology,'' published this month by the Russell Sage Foundation, has conducted an experiment in which some people who used a University of Michigan copying machine found a dime that researchers planted, while others were not given a dime to find.

After using the copier, people were asked how happy they were about life, and those who found a dime were consistently more upbeat about ''their lives as a whole, the economy, that kind of thing,'' Dr. Schwarz said. ''We've found that a dime can make you happy for about 20 minutes. Then your mood wears off.''

People tested in a study at the University of Illinois at Champaign-Urbana are given Palm Pilot handheld computers, which beep randomly several times in a day. After each beep, subjects fill out a questionnaire rating their happiness at that moment on a scale of one to seven. They are also asked what they were doing when they were beeped.

Dr. Kahneman, another co-editor of the ''Well-Being'' book, said research on moment-to-moment happiness could help scientists figure out all sorts of things. ''What is the mood of people when they ride in a Washington subway versus a New York subway?'' he asked, making a comparison between a subway that's new, clean and punctual and one that often is not. ''What is the effect on mood of having trees, of looking at water?''

Last year, Dr. Kahneman and a colleague published a paper on whether people are happier in California or the Midwest. ''We found not a particle of difference,'' he said. ''But everyone in California and the Midwest thinks that people are happier in California.''

Dr. Kahneman concluded that people asked about happiness often focus on one particular point, like the climate in California. But when it comes right down to it, Dr. Kahneman said, ''climate is just not very important to well-being.''

There do appear to be cultural differences across countries though.

Hamlet, it seems, was the rarest of creatures: an unhappy Dane. Surveys have found that ''Danes appear to be frightfully happy,'' said Mr. Argyle, citing a study in which 65 percent of the Danes interviewed said they were satisfied with life. By contrast, ''Italians and French seem miserable,'' he said, with only 10 percent giving life a thumb's up.

Americans tend to be a pretty positive bunch, while Asians are less sanguine.

''People in Japan report being less happy -- probably because they focus on the negative,'' said Dr. Diener, referring to several cross-cultural surveys that have been done. ''They think about their own shortcomings. Americans have bad points, but they don't tend to look at them too much.''

Photos: Who can resist puppies? Above, a test subject looks at an image in a happiness study by Richard J. Davidson at the University of Wisconsin at Madison. Left, a CAT scan shows the left frontal lobe of the brain, an area that correlates with subjects' reports of happy feelings. (Photographs by Andy Manis for The New York Times)(pg. B7); Richard J. Davidson, who is trying to find out what happiness is. (Andy Manis for The New York Times)(pg. B9)