Robert Emmons, PhD, a professor of psychology at the University of California, Davis, and psychology professor Michael McCullough of the University of Miami, have long been interested in the role gratitude plays in physical and emotional well being. They took three groups of volunteers and randomly assigned them to focus on one of three things each week: hassles, things for which they were grateful, and ordinary life events.

The first group concentrated on everything that went wrong or that irritated them. The second group honed in on situations they felt enhanced their lives, such as, "My boyfriend is so kind and caring—I'm lucky to have him." The third group recalled recent everyday events, such as, "I went shoe shopping."

The results: The people who focused on gratitude were happier. They saw their lives in favorable terms. They reported fewer negative physical symptoms such as headaches or colds, and they were active in many ways that were good for them. Those who were grateful quite simply enjoyed a higher quality of life.

Emmons was surprised. "This is not just something that makes people happy, like a positive-thinking/optimism kind of thing. A feeling of gratitude really gets people to do something, to become more pro-social, more compassionate." Such was not the case in either of the other two groups.