People use there hands to display masked emotions.

-someone who's relaxed tends to have open relaxed fingers, while someone who's wound up has tight fingers

-characters scratch their noses, crack there fingers etc. to give away masked emotion

-obsessive compulsive figures might scratch or pick at something

-often dropping the arms can be used to reveal a change in thought. The character is so floored by some revelation that they quit holding their arms up and gravity takes over.