ScienceDaily has an item (here) on D. Matsumoto’s comparison of blind and sighted Olympic and Paralympic judo athletes from 23 different countries.
“The statistical correlation between the facial expressions of sighted and blind individuals was almost perfect,” Matsumoto said. “This suggests something genetically resident within us is the source of facial expressions of emotion.”
Matsumoto found that sighted and blind individuals manage their expressions of emotion in the same way according to social context. For example, because of the social nature of the Olympic medal ceremonies, 85 percent of silver medalists who lost their medal matches produced “social smiles” during the ceremony. Social smiles use only the mouth muscles whereas true smiles, known as Duchenne smiles, cause the eyes to twinkle and narrow and the cheeks to rise.
“Losers pushed their lower lip up as if to control the emotion on their face and many produced social smiles,” Matsumoto said. “Individuals blind from birth could not have learned to control their emotions in this way through visual learning so there must be another mechanism. It could be that our emotions, and the systems to regulate them, are vestiges of our evolutionary ancestry.”
This does not mean that there are no cultural, learned instances of facial expressions. Obvious facial reactions are encouraged in some cultures and discouraged in others, for example, giving them a slightly different physical form and social use. I assume these are minor changes when looking at the really basic expressions.
But there is a sense in which facial expressions are more emotionally truthful than words. So when someone says that they really, really are not angry but their face, voice, posture and colour all show anger, they are probably deceiving themselves as well as you. Their introspection is less credible than your eyes.