Nonverbal behavior is widely recognized as conveying affective and emotional information, although it has other functions as well (such as regulating turn-taking in conversation).
As examples, a frown may convey disapproval or a smile may convey approval or agreement.
People often don’t display pure emotions through their nonverbal behavior or facial expressions.
This happens becouse our affective states are a mixture of varying quantities and strength of emotion.
We are able to convey opposing and overlapping emotions at the same time. For example, anger, is often accompanied by anxiety and fear.
The emotional overlap often creates confusing messages for the receiver.
The first scientific study on nonverbal communication and emotions was Charles Darwin’s book The Expression of the Emotions in Man and Animals (1872). He argued that all mammals show emotion reliably in their faces.
While some nonverbal messages is based on arbitrary symbols which differ from culture to culture, a large proportion is also to some extent iconic and may be universally understood. P aul Ekman’s influential 1960s studies of facial expression determined that expressions of anger, disgust, fear, joy, sadness and surprise are universal.
Other scholars found that even much other nonverbal signals are transcultural:
body movements such as pinching flesh, fidgeting, jiggling money or keys, tugging at your ears, wringing your hands, hunching over, chewing on a pen or other object, twiddling thumbs, or biting your fingernails can all convey nervousness, weakness and insecurity.
Below you will find a few of articles on emotions.

 . Authors: Russell JA, Fehr
Review: Journal of Personality and Social Psychology, 1994 Aug;67(2):186-205
Title: Fuzzy concepts in a fuzzy hierarchy: varieties of anger

. Authors: Smith CA, Haynes KN, Lazarus RS, Pope LK
Review: Journal of Personality and Social Psychology, 1993 Nov;65(5):916-29
Title: In search of the “hot” cognitions: attributions, appraisals, and their relation to emotion.

. Authors: Grossman M, Wood W
Review: Journal of Personality and Social Psychology, 1993 Nov;65(5):1010-22
Title: Sex differences in intensity of emotional experience: a social role interpretation.

. Authors: Izard CE, Libero DZ, Putnam P, Haynes OM
Review: Journal of Personality and Social Psychology, 1993 May;64(5):847-60
Title: Stability of emotion experiences and their relations to traits of personality.

. Authors: Larsen RJ, Ketelaar T
Review: Journal of Personality and Social Psychology, 1991 Jul;61(1):132-40
Title: Personality and susceptibility to positive and negative emotional states.

. Authors: Anderson AK, Phelps EA
Review: Letters to Nature, Nature, 411, 2001, pp. 305-309
Title: Lesions of the human amygdala impair enhanced perception of emotionally salient events

. Authors: Mauro R, Sato K, Tucker J
Review: Journ. of Personal. and Social Psycholology, 1992 Feb;62(2):301-17
Title: The role of appraisal in human emotions: a cross-cultural study

. Authors: Rime B, Philippot P, Cisamolo D
Review: Journ,l of Personal. and Social Psycholology, 1990, Jul;59(1):38-49
Title: Social schemata of peripheral changes in emotion