"For the current study, researchers created a list of 821 words to describe feelings and had these translated into other languages to download images across multiple cultures."

"With 7.2 million images of facial expressions from 31 countries, scientists used computer algorithms to discover that the human face can combine different muscles in different ways to express itself in 16,384 unique ways. When they sorted all these thousands of expressions into categories, the study authors expected to find several hundred variations of emotions. Instead, they were surprised to find only 35.... They concluded that most facial expressions are understood by all, and about half of these expressions are used to express joyfulness. The study found that happiness, whether expressed in a contented smile, glowing cheeks or crinkly eyes, is the face other humans find most recognizable. Researchers note that there are three expressions for fear, four for surprise and five each for sadness and anger. Disgust has only one expression."

From "Reason To Smile: Happiness Is The Most Dominant Human Expression, Study Finds" (in Study Finds).