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I guess I'm thinking that if you ask a child to draw a person frowning, you'll see the mouth turned down.
I guess you can frown without moving your mouth, but you can't have a smile on your mouth and a frown on your forehead. You have to have a "neutral" mouth.
Anyway, I thought these were by and large very good descriptions.
Your post sent me back to the mirror! Do you realize that while smiling you can raise your eyebrows without affecting your smile BUT if you frown while smiling your mouth has to move? (Yes, I know! I have way to much free time on my hands!!)
Re: Explanation of some words 
Linear Mode
