Not all smiles are created equal: The differences between enjoyment and nonenjoyment smiles

What is the meaning of the smile? Recent research has shown that one type of smile - the enjoyment smile - seems to be associated with positive emotion, whereas other types of smiles are not. On the basis of observations made by clinical neurologists on lesioned patients and by Ekman and Friesen (1982) on a large data set from normal subjects, it has been proposed that five distinct markers differentiate the enjoyment smile from other types of smiles: the presence of orbicularis oculi action in conjunction with the zygomatic major (Duchenne's smile), symmetrical action of the zygomatic major on both sides of the face, zygomatic major actions which are smooth and not irregular, duration of zygomatic major action that is consistent from one enjoyment smile to the next, and synchronous action of the zygomatic major and the orbicularis oculi such that they reach maximal contraction at about the same time. The research evidence supporting each of these markers is reviewed, and the advantages and disadvantages of utilizing each of these markers in research are discussed.