There's an anecdote I love. Samuel Fuller wanted to shoot a film with an arguing couple, and he's out at this farm, and while they're waiting to set up the next shot he discovers a chicken out in the yard chasing a cat around in circles. He sees this and says to his cinematographer, This is the perfect metaphor for the arguing going on inside—we shoot this, then we pull back into the room and see the actors. They do it and it's perfect. And if you'd written that into the script, the producers would have said, We've got to train a chicken to chase a cat? That's going to be expensive.
(joachim trier to lorin stein, "from the proceedings of the first annual norwegian-american literary festival," the paris review winter 2012)