Facial expression

But the yokel, being a yokel, was not good at the reading of facial expression, and only knew that a remarkably fine woman had gone by smiling.

The sullen clerk there did not return my greetings or my farewell, did not say a word, and did not show a single facial expression except irritation that I had interrupted his customerless routine.

2017, Jennifer S. Holland, For These Monkeys, It’s a Fight for Survival., National Geographic (March 2017)http://www.nationalgeographic.com/magazine/2017/03/macaques-monkeys-indonesia-endangered-pet-trade/ Facial expressions convey moods: Ritualized yawning—which starts with an oval mouth that breaks into a gaping one as the animal flings its head back—suggests tension.