Smiling Portrait

The Pan-Am smile, also known as the "Botox smile", is the name given to a "fake smile", in which only the zygomatic major muscle is voluntarily contracted to show politeness. It is named after the airline Pan American World Airways, whose flight attendants would always flash every jet-setter the same, perfunctory smile.
• Hidden emotions within smiling
Happiness is most often the motivating cause of a smile. However, there are many exceptions, especially among animals. The exposure of teeth, which may bear a resemblance to a smile, is often used as a threat or warning display—known as a snarl—or a sign of submission. For chimpanzees, it can also be a sign of fear. The study of smiles is a part of gelotology, psychology, and linguistics, comprising various theories of affect, humor, and laughter. Smiling can also be interpreted as nervousness in an animal - humans also smile as a result of nervousness and even embarrassment. In one study, created to investigate the correspondence between perceived meanings of smiles and their morphological and dynamic characteristics, it was found that “perceived embarrassed/nervous smiles had greater amplitude, longer duration…related to those perceived as polite.” Work by John Gottman has shown that smiling and other such expressions of positive emotions are important to shaping relationships with others; researchers could predict the quality of marriages many years into the future based on the number of such interactions (agreeableness).