
Excerpted from Errol Morris- NYT Opinionator Blog
PAUL EKMAN: In picture 2728 she is showing a social smile or a smile for the camera. The signs of an actual enjoyment smile are just not there. There’s no sign of any negative emotion. She’s doing what people always do when they pose for a camera. They put on a big, broad smile, but they’re not actually genuinely enjoying themselves. We would see movement in the eye cover fold. That’s the area of the skin below the eyebrow before the eyelid. And it moves slightly down only with genuine enjoyment. … In one of her pictures I get a chance to see her with no emotion on her face. That’s picture 4034. So I can see what the eye cover fold looks like when she’s not smiling. And it’s just the same as with the smile. That’s the crucial difference between what I call a Duchenne smile, the true smile of enjoyment, named after the French neurologist who first made this discovery in 1862, and the forced smile, the social smile.
(In “Emotions Revealed” Ekman quotes Duchenne: “The emotion of frank joy is expressed on the face by the combined contraction of the zygomaticus major muscle and the orbicularis oculi. The first obeys the will but the second is only put in play by the sweet emotions of the soul… The muscle around the eye does not obey the will; it is only brought into play by a true feeling, an agreeable emotion. Its inertia in smiling, unmasks a false friend.”)
http://opinionator.blogs.nytimes.com/2008/05/19/the-most-curious-thing/