He dives into the delightfully named fields of "happiness math" and "forgiveness studies." According to the data, once people reach a threshold of about $10,000 a year per person, money has little to do with contentment. People are happy if they are optimistic, grateful and forgiving. He quotes an expert in gratitude research: "if you only think about your disappointments and unsatisfied wants, you may be prone to unhappiness. If you're fully aware of your disappointments but at the same time thankful for the good that has happened and for your chance to live, you may show higher indices of well-being."

Gratitude research is part of the growing field of positive psychology, which focuses on the strengths of human beings. In simple terms, it's an empirical test of counting one's blessings.

"Grateful people are happier, more optimistic, more satisfied with their lives," says Michael McCullough, a University of Miami psychology professor. "They are more empathetic toward others. We even have a bit of evidence that grateful people are viewed as kinder, more helpful and more supportive than less-grateful people."

Gratitude has come under increased scientific study in the last five years, part of a trend in psychological research whose findings show the personal benefits of positive emotions.

"If you want a strategy to increase your happiness, there's a lot out there that will help. You can take pharmaceuticals like Prozac. But gratitude is something that doesn't have side effects," said Robert Emmons, a psychology professor at the University of California at Davis who, with McCullough, conducted the most widely cited study on gratitude. …

There's more to gratitude research than charting people's emotions to look for benefits. The professors involved say the findings have potentially profound ramifications on society.