A SMILE IS A FACIAL EXPRESSION FORMED BY FLEXING THE MUSCLES NEAR BOTH ENDS OF THE MOUTH AND BY FLEX-ING 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, SO-CIABILITY, HAPPINESS, OR AMUSEMENT, BUT CAN ALSO BE AN INVOLUNTARY EXPRESSION OF ANXIETY, IN WHICH CASE IT IS KNOWN AS A GRIMACE. SMILING IS SOMETHING THAT IS UNDERSTOOD BY EVERYONE DESPITE CULTURE, RACE, OR RELIGION; IT IS INTERNATIONALLY KNOWN. CROSS-CUL-TURAL STUDIES HAVE SHOWN THAT SMILING IS A MEANS OF COMMUNICATION THROUGHOUT THE WORLD.[2] BUT THERE ARE LARGE DIFFERENCES BETWEEN DIFFERENT CUL-TURES. A SMILE CAN ALSO BE SPONTANEOUS OR ARTIFICIAL.A SMILE IS A FACIAL EXPRESSION FORMED BY FLEXING THE MUS-CLES NEAR BOTH ENDS OF THE MOUTH AND BY FLEXING MUS-CLES 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 PLEAS-URE, SOCIABILITY, HAPPINESS, OR AMUSEMENT, BUT CAN ALSO BE AN IN-VOLUNTARY EXPRESSION OF ANXIETY, IN WHICH CASE IT IS KNOWN AS A GRI-MACE. SMILING IS SOMETHING THAT IS UNDERSTOOD BY EVERYONE DESPITE CULTURE, RACE, OR RELIGION; IT IS IN-TERNATIONALLY KNOWN. CROSS-CUL-TURAL STUDIES HAVE SHOWN THAT SMILING IS A MEANS OF COMMUNI-CATION THROUGHOUT THE WORLD.[2] BUT THERE ARE LARGE DIFFERENC-ES BETWEEN DIFFERENT CULTURES.

A SMILECAN 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 MUS-CLES 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, SOCIABILITY, HAPPINESS, OR AMUSE-MENT, BUT CAN ALSO BE AN INVOL-UNTARY 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 RESEMBLANCE TO A SMILE, IS OFTEN USED AS A THREAT OR WARNING DISPLAY—KNOWN AS A SNARL—OR A SIGN OF SUBMISSION. FOR CHIM-PANZEES, 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.[16] SMILING CAN ALSO BE INTER-PRETED AS NERVOUSNESS IN AN ANIMAL—HU-MANS ALSO SMILE AS A RESULT OF NERVOUS-NESS, EMBARRASSMENT AND EVEN FRUSTRATION

THE EVOLUTION OF SMILES IS OPAQUE AND, AS WITH MANY EVOLUTIONARY ACCOUNTS OF SOCIAL BEHAVIOR, FRAUGHT WITH JUST-SOISM. AMONG HU-MAN BABIES, HOWEVER, THE ‘TOOTH-BARING’ SMILE IS ASSO-CIATED 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 ALL SEEM TO HAVE TAKEN THE FRIGHT-THREAT SORT OF

SMILE AND EXTENDED IT TO STRANGERS AS A PRESUMABLY FRIENDLY SMILE. MAYBE IT IS NOT AS INNOCENT AS IT SEEMS.

“ALL CULTURES RECOGNIZE A VARIETY OF MOUTH GES-TURES AS INDEXES OF INNER EMOTIONAL STATES. AS IN OUR OWN CULTURE, HOWEVER, SMILES COME IN MANY VARIE-TIES, NOT ALL OF THEM INTER-PRETED 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 PROBA-BLY 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’ FEEL-INGS--THINK OF POLITICIANS SMILING FOR PHOTOGRAPHERS.

SMILES IN PRIMATES

“ “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 ASSOCIAT-ED WITH HAPPINESS AND EXCITEMENT.