This acting principle may make total sense and sound unnecessary to even mention. An animator controls everything the character does on screen and portraying human behaviour is a very difficult thing to do. Human behaviour isn’t predictable, as well as our actions we are constantly moving in small subtle ways. Body language, eye movement, changes in posture over time, subtle body movements, they all play a part in making up someone’s character. It should only make sense that as animators we pay attention to even the smallest detail to what our character is doing.
A character should play an action until something happens to make them play a different action. Every action we take is for a purpose, a goal. For example waiting at a bus stop, the action we are performing: sitting, has a goal behind it. The goal being to take the bus to our destination. The conflict in the scene would be that the bus hasn’t arrived yet and our character may be impatient, maybe he has something important to go to or a friend to meet. So our character would be performing an idle action until something happens to make him play a different action, in this scenario it’d likely to be the bus arriving. That’s what we’d expect to happen but perhaps there are other conflicts that come in the way of this goal (car splashing him with water, dropping money, etc.)
This is an acting principle that’s harder to show during my smaller animation exercises but it is applicable. I tried applying this acting principle to an animation I made this year for another project. The scene consists of a man typing away at a computer, he gets noticeably more intense with the typing until he presses the last button where something happens which causes him to flip a table.
The main in the scene is typing something, with the obvious goal of finishing whatever he is typing up. It could be something important or something he wants to say. I wanted the character to get angry so I made sure as he’s typing you notice he is visibly uptight: high shoulders and arched back which increases as he gets close to finishing the write-up. He then plays a different action upon noticing something go wrong (a blue screen, or crash, we’ve all been there).
I wanted his reaction to speak for the scene without showing what happened on the screen. Considering Ed Hook’s other acting principle “Acting is Doing, Acting is also Reacting”, I left the computer screen out of sight and had the character’s reaction tell the story. Other characters may react differently but as I had set-up the previous action with the character showing signs of irritation, this is the way I wanted this particular character to react.
The unseen action on the computer screen is the “something” that happens to make our character play a different action. As Ed Hooks remarks “the situation needs conflict to be theatrical” otherwise you only get “regular reality”.