Wrinkles should merely indicate where smiles have been.
~Mark Twain
I have been interested in the art of smiling since my first graduate school paper The Biological and Maturational Development of the Smile in the Neonate. You don’t really want to know how long ago that was, but to give you a rough idea — I wrote it while wearing my bellbottoms.
Back then I learned that infants initially smile as a type of reflex, almost as a way of getting them jump-started, but very soon afterward that grimace emerges into a social smile. They learn how to engage their caretakers, get some attention, be loved and, most importantly, survive. This means that a social smile has Darwinian value. But more than survival, a smile may be the doorway into understanding what brings us the good life.
Researchers LeeAnne Harker and Dacher Keltner (2001) analyzed college yearbook photographs of women displaying what is known as a Duchenne smile — an honest, genuine, bona fide smile — versus a non-Duchenne smile.