Over the course of history there have been many definitions of happiness, said Celestino Fernandez, Ph.D., a University of Arizona sociology professor.

But, the foremost happiness is an individual's unique experience that can be shaped, he explained.

Although subjective in its nature, happiness can be measured scientifically. The UA's School of Sociology studies happiness by asking direct questions, using scales and defining time periods.

"There is a high correlation between smiling, laughing and happiness," Fernandez said. "People who tend to be happy, laugh more frequently and smile more often."

Some reports indicate that 50 percent of happiness is set by genes, 40 by our own actions, and only 10 by the life circumstances beyond our control. Fernandez's research suggests that this distribution can be changed.

"Some people are prone to be happier than others, but even if they are less happy they can have impact on their level of being," Fernandez said. "One way to change brain patterns is through meditation."

The other is through exercise.

David Raichlen, Ph.D., a UA anthropology professor, studies evolutionary links between exercise and happiness.

"Exercise in the short and long-term periods can improve people’s moods, mostly through changes in neurotransmitter activity," Raichlen said. "Different chemicals get upregulated when we exercise and that help makes us happy."

This concept is rooted in the history of human beings, he said.

“Around two million years ago humans became hunter-gatherers as the landscape in Africa begun to open up," Raichlen said. "We used aerobic exercise and high level of aerobic activity to hunt and gather and get access to food resources."

His research suggests that if a person exercises somewhere between 70-80 percent of their maximum heart rate, the feeling of euphoria is induced.

A neurotransmitter, called endocannabinoid, is responsible for producing this sort of change in such mood.

Although there are ways to increase the level of happiness, either through meditation or exercise, reports show that we are less happy than we used to be, Fernandez said.

"In the United States, the happiness levels haven't changed over the last 50 years," he explained. "Roughly 30 percent of the population say that they are very happy, about 10 percent (say) that they are not happy at all, and the rest is somewhere in the middle."

To learn more about happiness from UA faculty join the first annual Downtown Lecture Series at the Fox Tucson Theatre, organized by the College of Social and Behavioral Sciences, kicking off Wednesday, Oct. 16.