Hmmm...i think there has been alot of scientific studies and research around it, but to me, its an art.
People arent robots, and no matter how many studies you do, you cant always determine exactly how someone will act.
I think it is an art to balance people, and work with them. Everyone has stresses and issues to deal with. I think helping people through that, professionally, is definately an art.
If it was a science, people would be able to learn how to do it 100 percent effectively. And in my experience, ive had some really terrible managers! I think it is definately an art.