I'm wondering how much reading fiction can help with that. I never really thought about it before reading HP:MoR which uses the argument quite extensively, but I do feel that my ability to understand others was greatly improved by the fact that, since early childhood (I remember being like 8 or 9 and spending a whole afternoon just devouring a book) I read a lot of fiction (mostly sci-fi, fantasy, adventure, and a bit of thrillers too).

Reading fiction, especially as a child, forces you to put yourself in the shoes of other people (usually the hero(es) of the book), which will vary greatly from book to book, and to make models of people (both the heroes and the secondary characters) to try to guess what will happen later in the book. It gives some kind of mental flexibility about understanding people, a bit like stretching gives flexibility to your muscles. And it does it much more efficiently than a movie to me, first because books can much more easily than movie speak about what's happening inside the head of the character (how he takes his decisions, what he feels, ...) and because a book gives you much more time to think about it than a movie.

Also, I think role-playing helps too. Even before playing "official" RPGs like D&D with dices and stats and everything, as a child, I was often "role-playing" in an intuitive way with my siblings, so putting myself in the shoes of someone else.

Those two may have a drawback : they may tend to lead me to have stereotyped views of others, to fall more easily to the halo effect, since often (but hopefully not always) the heroes have lot of qualities together, and the villains lots of flaws together.

Do any of you have a pointer to some deeper study about the link of reading fiction (especially as a child) with the ability to empathize with/understand others ?