In a new study, researchers have identified six different types of smiles.
Researchers at the University of California at Berkeley, Emiliana Simon-Thomas, a neuroscientist and Dacher Keltner, a psychology professor, have described the smiles and their distinctive characteristics.
The Duchenne smile, a genuine grin, it's named for 19th-century French scientist Duchenne de Boulogne, whose name is associated with a form of muscular dystrophy.
The flirty, coy smile, often, the person looks out of the corner of the eyes, head turned and the amused smile, it comes with the chortle after a good joke, with the head thrown back.
While those three expressions obviously convey signals to other people, Simon-Thomas said they're essentially "self-oriented."
"If you're making one of these smiles, you don't necessarily want to approach the other person to meet their needs," the Sydney Morning Herald quoted her as saying.
Contrast that with three kinds of 'pro-social smiles' that convey a desire to bond, there is, the love smile, often with a tilted head and softened eyes, the interested smile, with raised eyebrows and a slight grin and the embarrassed smile, sometimes with the eyes cast downward.
"The love smile is about embracing and caring, which we think is really different from the coy smile, which is more about getting sexual pleasure," Simon-Thomas added.