A smile is formed primarily by flexing the
muscles at the sides of the mouth. Some smiles include a contraction of the muscles at the corner of the eyes , an action known as a Duchenne smile.
Among humans , smiling is an expression denoting pleasure , sociability , happiness , joy or amusement . It is distinct from a similar but usually involuntary expression of anxiety known as a grimace . Although cross-cultural studies have shown that smiling is a means of communication throughout the world,there are large differences among different cultures, religions and societies, with some using smiles to convey confusion or embarrassment.