" What he meant was that the face has, to a large extent, a mind of its own. This doesn’t mean we have no control over our faces. We can use our voluntary muscular system to try to suppress those involuntary responses. But, often, some little part of that suppressed emotion — such as the sense that I’m really unhappy even if I deny it — leaks out. That’s what happened to Mary. Our voluntary expressive system is the way we intentionally signal our emotions. But our involuntary expressive system is in many ways even more important: it is the way we have been equipped by evolution to signal our authentic feelings. "

― Malcolm Gladwell , Blink: The Power of Thinking Without Thinking