A SMILE IS A FACIAL EXPRESSION FORMED BY FLEXING THE MUSCLES NEAR BOTH ENDS OF THE MOUTH AND BY FLEXING MUSCLES THROUGH-OUT THE MOUTH.[1] SOME SMILES INCLUDE CONTRACTION OF THE MUSCLES AT THE COR-NER OF THE EYES (SEE ‘DUCHENNE SMILING’ BE-LOW). AMONG HUMANS, IT IS AN EXPRESSION DENOTING PLEASURE, SOCIABILITY, HAPPINESS, OR AMUSEMENT, BUT CAN ALSO BE AN INVOL-UNTARY EXPRESSION OF ANXIETY, IN WHICH CASE IT IS KNOWN AS A GRIMACE. SMILING IS SOMETHING THAT IS UNDERSTOOD BY EVERY-ONE DESPITE CULTURE, RACE, OR RELIGION; IT IS INTERNATIONALLY KNOWN. CROSS-CULTUR-AL STUDIES HAVE SHOWN THAT SMILING IS A MEANS OF COMMUNICATION THROUGHOUT THE WORLD.[2] BUT THERE ARE LARGE DIFFER-ENCES BETWEEN DIFFERENT CULTURES. A SMILE CAN ALSO BE SPONTANEOUS OR ARTIFICIAL.A SMILE IS A FACIAL EXPRESSION FORMED BY FLEXING THE MUSCLES NEAR BOTH ENDS OF THE MOUTH AND BY FLEXING MUSCLES THROUGH-OUT THE MOUTH.[1] SOME SMILES INCLUDE CON-TRACTION OF THE MUSCLES AT THE CORNER OF

THE EYES (SEE ‘DUCHENNE SMILING’ BELOW). AMONG HUMANS, IT IS AN EXPRESSION DE-NOTING PLEASURE, SOCIABILITY, HAPPINESS, OR AMUSEMENT, BUT CAN ALSO BE AN INVOL-UNTARY EXPRESSION OF ANXIETY, IN WHICH CASE IT IS KNOWN AS A GRIMACE. SMILING IS SOMETHING THAT IS UNDERSTOOD BY EVERY-ONE DESPITE CULTURE, RACE, OR RELIGION; IT IS INTERNATIONALLY KNOWN. CROSS-CULTUR-AL STUDIES HAVE SHOWN THAT SMILING IS A MEANS OF COMMUNICATION THROUGHOUT THE WORLD.[2] BUT THERE ARE LARGE DIF-FERENCES BETWEEN DIFFERENT CULTURES. A SMILECAN ALSO BE SPONTANEOUS OR ARTIFI-CIAL. A SMILE IS A FACIAL EXPRESSION FORMED BY FLEXING THE MUSCLES NEAR BOTH ENDS OF THE MOUTH AND BY FLEXING MUSCLES THROUGHOUT THE MOUTH.[1] SOME SMILES INCLUDE CONTRACTION OF THE MUSCLES AT THE CORNER OF THE EYES (SEE ‘DUCHENNE SMILING’ BELOW). AMONG HUMANS, IT IS AN EXPRESSION DENOTING PLEASURE, SOCIABILI-TY, HAPPINESS, OR AMUSEMENT, BUT CAN ALSO BE AN INVOLUNTARY EXPRESSION OF ANXIETY.

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 re-semblance to a smile, is often used as a threat or warn-ing 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 linguis-tics, comprising various theories of affect, humor, and laughter.[16] Smiling can also be interpreted as nerv-ousness in an animal—humans also smile as a result of nervousness, embarrassment and even frustration

A SMILE IS FACIAL EXPRESSION FORMED BY INDIVIDUALS, WHERE THE EDGES OF THE MOUTH MOVE IN THE DIREC-TION OF THE CLOSEST EAR. SMILES ARE REPRESENTATION OF DIFFERENT EMO-TIONS, MOST COMMONLY ASSOCIATED WITH HAPPINESS AND EXCITEMENT.

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The evolution of smiles is opaque and, as with many evolution-ary accounts of social behavior, fraught with just-soism. Among human babies, however, the ‘tooth-baring’ smile is associat-ed less with friendship than with fright--which, one might argue, is related to the tooth-baringthreats of baboons. On the other hand, a non-toothy, not-so-broad-but-open-lipped smile is associated with pleasure in human infants.

Somehow we seem to have taken the fright-threat sort of smile and

extended it to strangers as a pre-sumably friendly smile. Maybe it is not as innocent as it seems.

“All cultures recognize a varie-ty of mouth gestures as indexes of inner emotional states. As in our own culture, however, smiles come in many varieties, not all of them interpreted as friendly. Baring one’s teeth is not always a threat. In primates, showing the teeth, especially teeth held together, is almost always a sign of submission. The human smile probably has evolved from that.

In the primate threat, the lips are curled back and the teeth are apart--you are ready to bite. But if the teeth are pressed together and the lips are relaxed, then clearly you are not prepared to do any damage. These displays are combined with other facial features, such as what you do with your eyes, to express a whole range of feelings. In a lot of human smiling, it is something you do in public, but it does not reflect true ‘friendly’ feelings--think of politicians smiling for photographers.

SMILES IN PRIMATES