We begin with the type of smile known as the “Duchenne” smile. It is named after Guillaume Duchenne, a French neurologist. He noticed that most people smile with their eye muscles and their mouth muscles simultaneously. Therefore, the Duchenne smile occurs when people’s eyes “crinkle” when they smile. This smile can not be faked, and you can always tell when someone who smiles like this is smiling genuinely. Just look at the eyes.
The Pan Am smile is the opposite to the Duchenne smile, in that it is fake as opposed to genuine. With this smile, the eyes do not move, and it is only the mouth that “smiles.” This smile was named after flight attendants, since they often fake their smiles, although these fake smiles are hard to spot and seem real.
The Botox is almost identical to the Pan Am smile, except for the fact that it’s not forced. The botox smile is relaxed and natural, it just doesn’t include the movement of the eye muscles. It may just be someone who regularly smiles with a Duchenne smile, but is tired or drained, and so doesn’t use the eye muscles as usual.