In the mid 19th century, French neurologist Guillaume Duchenne wanted to distinguish real smiles from fake. Interested in the response of nerves and muscles to stimulation, he applied electricity to particular parts of faces to see the results.
원문출처 : https://www.cnn.com/2018/06/13/health/types-of-smile-partner-intl/index.html
원문출처 : https://www.cnn.com/2018/06/13/health/types-of-smile-partner-intl/index.html