Film critic Roger Ebert has a terrific little essay on moments of goodness in film:
I've been saying for years that I never cry during sad moments in the movies, only during moments about goodness. At the end of "Terms of Endearment," I didn't cry because of Debra Winger's death, but because of how she said goodbye to her sons. Now I've have discovered a scientific explanation for why I feel the way that I do, and there is even a name for my specific emotion.
I wasn't seeking an explanation, and I'm not sure I really wanted one. And, for that matter, I don't really cry, at least not in the wiping-my-eyes and blowing-my-nose fashion. What I experience is the welling up of a few tears in my eyes, a certain tightness in my throat, and a feeling of uplift: Yes, there is a good person, doing a good thing. And when the movie is over, I don't want to talk with anyone. After such movies I notice that many audience members remain in a kind of reverie. Those who break the spell by feeling compelled to say something don't have an emotional clue.
The scientific explanation, it turns out, is from Greater Good's Dacher Keltner. The whole piece is well worth a read.