Say Cheese

You can't fake it, unless you're a con man or a psychopath

From Wired (UK) via the Dish...

People think they can tell by looking at what the overall face looks like, but in fact there is one muscle [that shows sincerity]. It's a muscle, called the obicularis occuli, that encircles the eye socket. Most people don't pay very close attention to and it's very hard to deliberately adopt. So when people genuinely smile, in a true burst of positive emotion, not only to the corners of the mouth, controlled by the zygomaticus major, but this muscle around the eye also contracts. This causes the crows feet wrinkles that fan out from the outer corners of the eyes and its also responsible for folds in the upper eyelid. Most people can't do that deliberately.

The muscle doesn't seem to be under voluntary control normally, but with training and practice, people can learn to use it, some better than others. And of course your garden variety psychopath or Machiavellian personality tends to be better at it. A characteristic of con men is that they somehow manage to exude a positive, good feeling to get themselves into your good graces, only to exploit it.