Twenty-six years ago, when psychologist Robert Enright, PhD, first got interested in forgiveness, his colleagues thought he'd lost his mind. "They said, 'How can a scientist study something so fluffy?'" he recalls. Enright, who's now a professor of educational psychology at the University of Wisconsin–Madison, takes something of a philosophical approach to his subject. He sees forgiveness as a moral imperative first (turn the other cheek because it's the right thing to do) and a practical matter second (and, oh yes, doing so will probably make your life better). "The decision to forgive touches you to your very core, to who you are as a human being," he says. "It involves your sense of self-esteem, your personal worth, the worth of the person who's hurt you, and your relationship with that person and the larger world."

Much of Enright's research has focused on people who forgive the seemingly unforgiveable—people like Marianne Rosen, 52, who volunteered for one of Enright's earliest studies at UW–Madison in the early 1990s. Rosen's father began sexually and emotionally abusing her when she was 5 years old, and by the time she was in her late 20s, she'd resigned herself to living with rage, hurt, and fear for the rest of her life. Enright wondered if forgiveness could help in such an extreme case: "The literature at the time basically said, 'There's very little the psychological sciences can do for someone so gravely wounded.'"

The study Rosen volunteered for compared incest survivors who were offered forgiveness training with those who weren't. For more than a year, Rosen met weekly with Suzanne Freedman, PhD, then a graduate student of Enright's, now an associate professor of educational psychology at the University of Northern Iowa. The goal of the meetings was to allow Rosen to relive her pain and experience her grief in a safe place; somewhere along the way, Rosen made an intellectual decision to forgive her father, who had committed suicide when she was 11. "The work enabled me to see that he was not able to break the chain of abuse," she says. "And I got to a point where I actually wanted to see him. So I went to Chicago and found where he was buried, and put a pebble on top of his headstone. I remember just sobbing and finally feeling there was some kind of resolution." After years of feeling simmering resentment toward her father, she says, "I just wasn't angry anymore."

Like Rosen, the other participants in Enright's study made surprising emotional progress. Those who had gone through the forgiveness training felt less anxiety and depression, and more hope and higher self-esteem, than those who hadn't. A year later, the gains still held. The study had changed the participants' lives.

But how? Researchers are now using functional magnetic resonance imaging to see if the answer lies within the brain. A team at the University of Pisa in Italy asked people to imagine forgiving someone and then observed changes in cerebral blood flow, which signaled the parts of the brain that became more active. They found that several regions "lit up," especially areas that regulate emotional responses, moral judgments, perceptions of physical pain, and decision making. By creating this kind of neural map, researchers hope to learn more about how forgiveness works on both a physical and a psychological level.

Kathleen Lawler-Row, PhD, a psychology professor at East Carolina University, is one of several researchers exploring the relationship between forgiveness and health—physical, emotional, and spiritual. She thinks the effects of forgiveness go beyond lowering blood pressure and improving sleep. Once you forgive someone for something very painful, "you never experience life the same way again," she says. "You're more flexible, less black-and-white in your expectations of how life or other people will be. If there's one thing that characterizes people who have experienced forgiveness, it's that kind of larger perspective: I can't predict what life will hand me, but I'm going to respond to it in this way."

Like Luskin, Enright, and others, Lawler-Row believes that forgiveness is at heart a choice, one that any of us can make at any time, no matter the "content" we're wrestling with. How do we do it? Maybe the choice depends in part on how we define the idea. Forgiveness doesn't mean rationalizing or condoning abuse. And forgiveness doesn't mean a sudden case of amnesia. Marianne Rosen knows exactly what her father did and what he was capable of. She can't forget that, but she can change the story of her future. "Forgiving enabled me to realize I could create my own path," she says. "I wasn't just plopped down on this cruddy path I had to walk the rest of my life. I was in control."