What is Smile?
[[File:La Gioconda.jpg|thumb|The most famous smile in [[art]]: the [[Mona Lisa]]: [[wikt:subtle|subtle]] and [[ambiguous]]]] [[File:Smiling girl.jpg|thumb|An extreme smile: mouth wide open with teeth showing; perhaps a [[laugh]] or happy [[wikt:shriek|shriek]]]] {{other uses}} A '''smile''' is a [[face]] made by flexing the [[muscle]]s near both ends of the [[mouth]].<ref>Freitas-Magalhães A. & Castro E. 2009. The neuropsychophysiological construction of the human smile. In A. Freitas-Magalhães (ed) Emotional expression: the brain and the face. 1-18 Porto: University Fernando Pessoa Press. {{ISBN|978-989-643-034-4}}</ref> The smile can also be made through the [[eyes]] (See 'Duchenne smile' below). Smiles usually express [[happiness]]. A smile can be natural or fake. However, smiling can be different with [[animal]]s. When smiling, the [[teeth]] shows, but sometimes animals do this when they are [[threat]]ening. When [[chimpanzee]]s show their teeth, it can also be a sign of [[fear]]. == Dimples == {{main|dimples}} [[Image:VirgilGriffithFace.jpg|thumb|220px|A man smiling]] [[File:Palestinian girl in Qalqiliya.jpg|thumb|Girl smiling]] Dimples are [[genetics|genetically]] [[heredity|inherited]].<ref>{{Cite web |url=http://www.science.edu.sg/ssc/detailed.jsp?artid=4862&type=6&root=4&parent=4&cat=40 |title=Singapore Science Centre: ScienceNet{{!}}Life Sciences{{!}}Genetics/ Reproduction<!-- Bot generated title --> |access-date=2010-11-13 |archive-date=2003-09-25 |archive-url=https://web.archive.org/web/20030925150701/http://www.science.edu.sg/ssc/detailed.jsp?artid=4862&type=6&root=4&parent=4&cat=40 |url-status=dead }}</ref> They are caused by the flesh underneath the skin, that forms on some people's cheeks, especially when they smile. Some people may only have one dimple on only one side of the face. == Duchenne smile == Although there are many different types of smiles, researchers are interested in the duchenne smile because it is done with the eyes. The Duchenne smile was named after the French physician [[D