Duchenne smile

n. An authentic smile characterized by symmetrical upturns of the corners of both sides of the mouth and symmetrical tensing of the orbicularis oculi muscles, causing crinkling at the corners of the eyes, which is recognized as an expression of happiness in all cultures. These smiles are contrasted with posed, social, or phony smiles, in which there are less involvement of the eyes and often an asymmetrical or exaggerated upturn of the corners of the mouth.