What exactly is happening inside the brains of people experiencing joy and happiness?
"It's a very complicated chemical soup," explained Dr. Richard Davidson, who has made a life's work out of studying "happy brains." His lab at the University of Wisconsin is devoted to understanding how much of our joy level is set at birth, and how much we can control.
With a skull cap containing 128 sensors, Davidson's team can watch a subject's brain respond to a series of photographs, some pleasant, some distressing.
"We can challenge the brain by presenting these emotional images and look to see how you respond to them," Davidson said.
ABC News' Bill Weir underwent the test, and by studying the activity in his left prefrontal cortex, Davidson discovered that Weir's brain was "more positive than not."
"Now, it doesn't mean that you don't have episodes of negative emotion," he explained. "But those negative emotions don't linger."
People with happy brains have their parents to thank, to a certain extent, not only for happy genes, but also for loving childhoods. Studies have shown that angry or critical parents can actually alter a child's happiness level until it's set around age 16. But can adults adjust their own feelings of happiness?
Until recently, most research psychologists were more interested in what made people depressed than what made them happy, and pharmaceutical companies have played a crucial role in promoting happiness by developing very successful anti-depressants. But evolving research in a field known as positive psychology is getting people to ask themselves how they can become happier, not through drugs, but by making changes in how they act and think.
"Antidepressants don't make people happier, they just decrease negative emotions," says University of California-Riverside psychology professor Dr. Sonja Lyubomirsky. In her new book, "The How of Happiness," Lyubomirksy argues that as much as 40 percent of our happiness "is left for the intentional activities that we can choose to engage in -- the things that we do and think every day of our lives." (How happy are you? CLICK HERE to see where you fall on Lyubomirisky's Subjective Happiness Scale."
What are these "intentional activities"? Scientists know that happy people practice, among other things, more acts of kindness, are able to lose themselves in whatever they enjoy doing, and avoid dwelling on their problems.
Lyubomirsky has had lab subjects actually engage in some of these activities, and found that people can indeed force themselves to truly become happier. Not surprisingly, such happiness interventions take work, because people easily fall back to their genetically-determined happiness set points. Scientists have known for decades that a large part of our temperament is genetically pre-determined; by studying the personalities of identical twins they've found that about 50 percent of our happiness -- or unhappiness -- can be traced to our genes. Adding the 40 percent that we can control with our daily thoughts and actions still leaves about 10 percent unaccounted for. This remaining 10 percent is related to our life circumstances, such as where we live, how much money we have, our marital status, and how we look.