When I joined Custer I donned the uniform of a soldier. It was a bit awkward at first but I soon got to be perfectly at home in men's clothes.
You can still have chemistry on screen without getting on with the person. But it just makes your job a lot easier if you don't have to gird your loins, if that's not quite the right phrase, every time you're going to do a scene with that person.
I believe that the brain has evolved over millions of years to be responsive to different kinds of content in the world. Language content, musical content, spatial content, numerical content, etc.

