Yes I think you are right, I watched a documentary by Desmond Morris that featured something about the genuine smile and the fake smile, a genuine smile will also have "smiling eyes" he said.
It was a fascinating BBC documentary called "The Human Animal" he pointed out that when a person is lying to you, they will blink a bit more than they usually do, they also have a tendency to cover their mouth with their hand as if to "hide" their lying mouth.
There was also a poker game featured on the documentary, and they pointed out that when a card player has a losing set of cards, he will put his chips down with a flourish..(for those who might not know the word flourish...it means to put the chips down with a kind of "Bah! Whats the use?" attitude..)
Hey I think I found the start of that documentary on youtube..http://www.youtube.com/watch?feature...&v=x85T7DR4opA