Reprinted from Greater Good Magazine, Vol. IV, Issue 1. Used with permission.

Research in positive psychology has identified several ways that practicing gratitude can boost people's health and happiness. Here are four of these research-tested "gratitude interventions."

1. Write a gratitude letter.
Research by Martin Seligman, Christopher Peterson, and others has shown this one to be particularly effective. Write a letter to a mentor, family member, or some other important person in your life whom you've never properly thanked. Deliver it in person. Read it out loud. Bring tissues.

2. Keep a gratitude journal.
Studies by psychologists Michael McCullough, Robert Emmons, Sonja Lyubomirsky, and others have backed up this exercise, which involves keeping a list of things for which you're grateful—anything from your children or spouse to the beauty of the tree outside your window. Doing so helps you focus on the positive things in your life—a practice that's been shown to increase happiness.

3. Savor.
Take the time to notice beauty and pleasures in your daily life. Loyola University psychologist Fred Bryant has shown that savoring positive experiences can heighten your positive responses to them. A key to savoring is what Bryant calls "thanksgiving," or expressing gratitude for the blessings that come your way, large and small.

4. Think outside the box.
It's fairly obvious why we might feel grateful for grandmothers, lovely sunsets, and anything else that has provided comfort or beauty in our lives. But what about thanking the homeless people who come to the shelter where you volunteer? "Individuals who do volunteer work sometimes speak of the benefits they receive from service," writes Robert Emmons in his forthcoming book, Thanks! "Since service to others helped them to find their own inner spirituality, they were grateful for the opportunity to serve." If we look hard enough, he argues, we can find a reason to feel grateful for any relationship—even when someone does us harm, as that person helps us appreciate our own vulnerability. Emmons claims that such highly advanced forms of gratitude may actually increase the level of goodness in the world by inspiring positive acts in ourselves and others.