According to Dr. Paul Ekman (an American psychologist expert in the study of emotions and was professor of Psychology at the University of California) there are seven universal emotions, he “found out” and defined the existence oh these emotions. He has some books written by him. One of my favorites is called: Emotion in the Human Face: Studies in Emotion and Social Interaction. This book describes this emotion in a detailed way and I am going t give you guys a brief explanation of the basic emotions describe by Dr. Ekman.
Happiness: an authentic smile is characterized “by the inadvertent activation of two muscle groups,” there is an elevation in both corners of the mouth, symmetrically and the second group, brand wrinkles at the corners of the eyes (crow’s feet).
Anger: the stress is concentrated on the eyebrows symmetrically approaching. You can also see tension on the lips, the pressure of one over another draws a horizontal straight line in the mouth.
Fear: evolutionary speaking, our eyes are prepared to identify any threat, it is why both eyes become large extending upward. Lips, like anger, draw a horizontal line but this microexpression, the mouth is slightly open.
Sadness: the corners of his mouth go down and eyebrows are slightly up but only in its internal limits.
Depression: is unilateral, the corners of the mouth extending to one side of the face. Contempt by its English name has to do with the repression of emotions, arrogance or a feeling of moral superiority (depending on context).
Repugnance: the feelings of this microexpression are related to disgust, so the tension of the face can be seen on the nose (it’s like trying to hold back a smell), upper lip accompanied by an upward movement of the nose. Disgust is very close to hatred.
Surprise: The microexpressions of surprise and fear are easily confused because both raised our eyebrows, but the reasons are very different, we put ourselves in fear alert to a potential threat and surprise we prepare to receive unexpected information. a clear tension on the fear in the pit, while the surprise we open our mouths in a relaxed manner.
If you are interested in knowing more about emotions, I totally recommend you to Read the book that is available in many book stores in the physiology section.
References:
References taken from “Emotion in the Human Face: Studies in Emotion and Social Interaction” writen by Dr. Paul Ekman.
Body Language 