Research on smiling started as far back as the mid-1800’s. A French doctor named Duchenne used electrical currents with research subjects. He would stimulate certain facial muscles and then take pictures of the expressions that people made. This was painful and many of the pictures look like the people are in pain.
Real or fake? — Duchenne identified two different types of smiles. Some smiles involve contraction of both the zygomatic major muscle (which raises the corners of the mouth) and the orbicularis oculi muscle (which raises the cheeks and makes your eyes crinkle). Smiles that contract both of these muscle groups are called “Duchenne” smiles. In a “non-Duchenne” smile only the zygomatic major muscle contracts, in other words your mouth turns up, but your eyes don’t crinkle.