Facial Expression of Happiness

Smiling is the universal sign of happiness. A genuine smile involves the voluntary contraction of the “zygomatic major” muscles (sides of the mouth rising) and the involuntary contraction of the “orbicularis oculi” muscles (raising of the cheeks to produce crow’s feet at the eyes). A fake smile is only due to the voluntary contraction of the zygomatic major. The brain’s motor cortex controls a fake smile, whereas genuine smiles are governed by the limbic system. Research has shown that the feelings of happiness underlying true smiles tend to be “contagious,” causing people who observe a smile to become happy themselves.