Though positive psychology is only beginning to be used as an educational tool in classrooms and secondary schools, in the nine years since Seligman’s epiphany it has taken a firm hold in academia. The field’s steering committee includes a number of psychologists and psychiatrists who have done highly regarded clinical work: Ed Diener of the University of Illinois at Urbana-Champaign, whose specialty is “subjective well-being”; Christopher Peterson at the University of Michigan, who has made a study of admired character traits around the world; George Vaillant, who has long headed a Harvard project tracking success and failure among the college’s graduates; and Mihaly Csikszentmihalyi of Claremont Graduate University, who has spent years studying “optimal functioning,” or the state of being intensely absorbed in a task, what he calls “flow.” Seligman’s book, “Authentic Happiness,” published in 2002, lays out the field’s fundamental principles and has been translated into nearly 20 languages. Last year’s annual positive-psychology summit in Washington attracted hundreds of academics working in the field or interested in doing so, as well as a children’s programming director, who was working to imbue her cartoons with positive psychology messages, and the Nobel Prize-winning economist Daniel Kahneman, who studies the relationship between economics and perceptions of happiness. In addition there were a lot of “life coaches,” independent consultants who hire themselves out to help clients achieve their life goals.

Despite its seemingly American emphasis on self-reliance and self-expression, positive psychology is also proving popular in England and the British Commonwealth. Nick Baylis, a psychologist at Cambridge University, helped found the Well-being Institute there last year and is consulting with Wellington College, a private boarding and day school, on how to apply positive psychology to its curriculum. The Geelong Grammar School, a prestigious boarding and day school in Australia, is planning to shape its curriculum around the precepts of positive psychology in 2008, and the government of Scotland has also been in touch with Seligman to see whether the discipline might help its citizens. “Our old nation has been renewed through our new Parliament, and if we can embrace this new science of positive psychology, we have the opportunity to create a new Enlightenment,” one government official announced.

Positive psychology is popular with educators because if happiness is something that can be learned, it can be taught. And because being happier seems to have positive long-term effects not just on well-being but also on health and life span. In one often-cited study, researchers at the University of Kentucky analyzed the essays novices born before 1917 wrote on entering the School Sisters of Notre Dame and correlated them to the nuns’ life spans. They found that 9 out of 10 of the most positive 25 percent of the nuns were still alive at 85, while only one-third of the least positive 25 percent were. Overall, their study showed positive emotions correlated to a 10-year increase in life span, greater even than the differential between smokers and nonsmokers. Another study, by Dacher Keltner, a psychology professor at U.C. Berkeley, correlated the smiles that the female graduates of Mills College in Oakland, Calif., displayed in two mid-20th-century yearbooks with life satisfaction and found that the bigger the smile, the more satisfying the marriage and the greater their well-being. Inspired by studies like these, positive psychologists have developed “interventions,” or practices, designed to maximize positive emotions and have tested them on thousands of people. One such intervention is to think every night about the good things that happened to you that day. Another is to make sure in any given day that you either work or play in a new area that draws on what positive psychologists call your “signature strengths” to create a sense of well-being. Gratitude visits — looking up someone who has taught or mentored you and thanking him or her — are important in positive psychology, too; this last intervention, studies show, gives the biggest increase in happiness of all.

In the first few weeks of the semester, Kashdan asked his students to keep a record of their thoughts and experiences. He then gave them “experiential assignments” to make them happier, working their emotions the way an athletic coach might work their muscles. One week they were to report on attempts to go into “flow.” “Sex, drugs and chocolate are all highly useful avenues for people to attain flow states,” Kashdan said. To enter flow, students were asked to do something that they were good at, be it writing, playing basketball or talking to their friends. According to positive psychology, your signature strengths play a special role in building your confidence and thus bringing you happiness. Seligman’s Web site, authentichappiness.org, has a 240-question test to help determine whether your gift is for creativity, bravery, love or something else. In class, one student recounted going into flow during a fistfight; another told of being at her father’s grave. A third talked about being with a friend watching TV and suddenly having a profound conversation. “We had so much love for each other,” the student remembered in class, “and suddenly we were crying.”

Several studies undertaken by positive psychologists have suggested that meditation enhances well-being, so another class assignment was to meditate for 15 minutes three days in a row, attend a free yoga class (Kashdan’s wife, a yoga instructor, arranged this with her studio), be mindful twice a day and report on the results. The mindfulness exercises — excercises in heightened awareness and openness to experience — are central to positive psychology and made a big impression, according to Kashdan: “Some said they just noticed for the first time how many types of trees there are on the way to campus.”

The following week, students were asked to watch “Before Sunrise” and “Before Sunset,” movies starring Ethan Hawke and Julie Delpy. In the former, the two fall in love through intense conversation during one long evening in Vienna and then part. The sequel catches up with them nine years later. The students had to write about the first time they fell in love. The next assignment was to pay a gratitude visit or write a gratitude letter. After that, the students were to exercise their curiosity by doing something “novel, complex, and uncertain . . . epistemic, sensory and social” — that is, they were to use their signature strengths to try something new. One student tasted a pomegranate for the first time; another went to a book reading by Carly Fiorina, the former C.E.O. of Hewlett-Packard. Finally, the students were asked to select one memory they would be willing to spend an eternity with, an intervention inspired by the Japanese movie “After Life.”

Kashdan’s enthusiasm — he is a passionate teacher — ate up class time, and so the students never got to other parts of the syllabus, among them optimism exercises and exercises that would make them better teammates. On the last week, students handed in their final papers, describing how they had tried to enhance their lives toward, in Kashdan’s words, “a specific, personally meaningful positive outcome” during the semester. There was no final exam; the students’ grades were based in large part on the paper and class participation.