Excerpt from Michael Caine’s awesome book Michael Caine – Acting in Film: An Actor’s Take on Movie Making :
The modern film actor knows that real people in real life struggle not to show their feelings. It is more truthful, and more potent, to fight against the tears, only yielding after all those defense mechanisms are exhausted. If today’s actor emulated film, he’d be better off watching a documentary. The same is true of drunkenness. A coarsely acted stage or film drunk reels all over the place to show you he’s drunk. It’s artificial. And eventually, that kind of acting puts up a barrier between the actor and the audience, so that nothing the character says or does will be believed…
Audiences themselves have had a lot to do with the changes in film acting. They catch on very fast to what is truthful and what is not.
Once audiences saw acting like Henry Fonda’s in The Grapes of Wrath, they tuned in to the difference between behavior that is based on carefully observed reality and the stagier, less convincing stuff.
Marlon Brando’s work in On the Waterfront was so relaxed and underplayed, it became another milestone in the development of film acting. Over the years, the modern cinema audience has been educated to watch for and catch the minute signals that an actor conveys. By wielding the subtlest bit of body language, the actor can produce an enormously powerful gesture on the screen.
In The Caine Mutiny, the novel’s author tells us that Captain Queeg plays nervously with two steel balls in his hand. In the film, Humphrey Bogart knew that most of the time, just the click of those balls on the sound track was all the audience would need — he didn’t even have to look neurotic.
I remember reading an interview with Keenan Wynn where he talked about directing his father in Requiem for a Heavyweight and he commented that his biggest problem was getting his dad to stop with all the little fussy bits and just go with the action. He knew that the little fussy bits his dad had used in vaudeville just screwed up the whole show.