From Cosmo MacLellan
Smiling is one of the most basic of human expressions, and is thought to be related to the ‘silent bared-teeth display’ in other primates. Opening the mouth to show off closed teeth is a non-threatening signal of cooperation, and for us, it has become a reflex way to express happiness. There’s a difference between spontaneous smiles and forced smiles. Natural smiles are more symmetrical and involve wrinkling at the outer edges of the eyes. It’s difficult to ‘fake’ a smile convincingly, and people are normally able to distinguish between the two. However, even though people might be able to tell your smile isn’t natural, it is not wasted. Smiling at the right time is a social signal of cooperation, and can trigger a positive response in the people around you. It also affects your mood. Smiling is thought to have a feedback effect on the brain, making you feel happy.
Answered by Laura Mears for Brain Dump in How It Works Issue 97