If you're working in close-ups, then an actor is only able to act with his head. I like an actor to act with their entire body.
When you act, your whole body is the instrument.
It's something that I learned even before I started acting: the movement, the dance of the body, is very important, and it comes before words.
My mother was a dancer, so I like to use the body as part of the instrument of acting.
I do use my body a lot, to click into a character.
Even in cerebral roles that are seemingly intelligent and nothing else, I think it's so important to wrap your characterization in a physical form as well.
Even the cerebral characters I play seem to have physical quirks. They're all "physically inhabited," for lack off a better expression. For instance, Sherlock Holmes has very particular physical gestures which are drawn out in such detail.
Words and action in movies are the spirit or the mind. And these days the body is almost completely forgotten. In the beginning the body - nature - was more part of the action.