Acting isn’t just about the face. It’s also body language. At any given point, the human form is involved in ‘acting out’, or communicating emotion. If you think it’s enough to observe just the facial expressions, try acting in front of a mirror. Let’s try anger. Do you feel your neck edging forward, or some neck muscles stretching? Some tension in your flexor group of muscles in the lower arm? Is your whole body moving forward? Now you see it, don’t you? This is gesture drawing.