Research shows that helping others makes us happier. But in her groundbreaking work on generosity and joy, social psychologist Elizabeth Dunn found that there's a catch: it matters how we help. Learn how we can make a greater impact -- and boost our own happiness along the way -- if we make one key shift in how we help others. "Let's stop thinking about giving as just this moral obligation and start thinking of it as a source of pleasure," Dunn says.