In the movie Pay It Forward, the plot is based on doing three good deeds for strangers, asking only that they do the same for three others in return. "Research absolutely supports this idea," says Sonja Lyubomirsky, PhD, professor of psychology at the University of California, Riverside, and the author of The How of Happiness. "It's called the upward spiral effect."

The cross-pollination between cinema and brain science has even given rise to the publication Projections: The Journal for Movies and Mind. "We feel," says editor Ira Konigsberg, PhD, "that art offers us the opportunity to increase our understanding of the brain, and vice versa."