From Wikipedia, the free encyclopedia.
This article is about a smile as a physiological phenomenon. For information on the album, see Smile (album).
In physiology, a smile is a facial expression formed by flexing muscles near both ends of the mouth. Customarily, it is an expression of pleasure or amusement.
Researchers have identified a number of different types of smile. The "Duchenne smile" is the most studied, it involves the movement of both the zygomatcus major muscle near the mouth and the orbicularis oculi muscle near the eyes. It is believed that the Duchenne smile is only produced as an involuntary response to genuine emotion.
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