So, I mentioned earlier that it seems we're unable to put mascara on without opening our mouths. Being the way I am, I had to know why. I asked someone who knows more about makeup than I do (which isn't saying much) and she had the skinny!
It turns out that your eye muscles actually relax when you open your mouth. Try it. Focus on your eye muscles and then open your mouth. You can feel everything go slack up there in eye-land. Pretty interesting stuff.
Turns out it IS a biological imperative! I love it when I say idiotic things that turn out to be correct!