[ScienceD] Researchers crack the smile, describing three types by muscle movement

[Science Daily]

Researchers crack the smile, describing three types by muscle movement

The smile may be the most common and flexible expression, used to reveal some emotions, cover others and manage social interactions that have kept communities secure and organized for millennia. But how do we tell one kind of smile from another?

http://feeds.sciencedaily.com/~r/science...184835.htm