Specialization

Back in April, I met Tom Leveen (www.tomleveen.com) author of Party and Zero. He graciously agreed to visit my creative writing class at the end of the semester, and it was during that time that he made one of the most profound statements about writing dialogue. He developed his dialogue chops with his theater background.
When I write, everyone tells me my dialogue sounds and feels natural, and is one of my greatest strengths. I never had a clue as to why until Tom talked about his theater background.
I don't have a theater background.
But I do have a background in drama literature.
I've always loved plays, even in high school, and relished reading them, especially Shakespeare. My undergrad focus in literature was drama and Shakespeare. Three different Shakespeare classes and half a dozen other drama literature classes including modern drama, Renaissance drama, and restoration drama.
Tom was right that there's nothing on the page but dialogue. When you read drama, you are forced to rely only on those words.
But this has started me thinking (yes, always dangerous).
Are there other specializations of writing that develop generalized fiction writing skills?