What exactly is a smile for, how do we do it and if we lose it, can we get it back?
It’s one of the most fundamental things that humans do. Smile. Newborns can manage it spontaneously, as a reflex, and this is sometimes misinterpreted by new parents as a reaction to their presence, although it’s not until six to eight weeks of age that babies smile in a social way. That new parents optimistically interpret the first reflex smiles reflects the complexity of smiling: there is the physical act and then the interpretation society gives to it – the smile and what the smile means.
On a physical level, a smile is clear enough. There are 17 pairs of muscles controlling expression in the human face, plus the orbicularis oris, a ring that goes around the mouth. When the brain decides to smile, a message is sent out over the sixth and seventh cranial nerves. These branch across each side of the face from the eyebrows to the chin, connecting to a combination of muscles controlling the lips, nose, eyes and forehead.