Although it can be faked, it is believed that the Duchenne
smile (named after the French researcher Guillaume Duchenne) is the only form of what one could call the “genuine” smile. It is achieved
when you curl your upper lip inward and smile with your mouth as much as with your eyes. The “Pan American Smile,” on the other hand is the smile expressed to show politeness, for example by a flight attendant on the former airline with the same
name. It only involves the muscles of the mouth and not the eyes.
Whenever you smile, do it with your eyes as much as with your mouth, knowing that this “genuine smile” has a direct positive impact on your brain.