Abstract
The purpose of this study is to clarify the mechanism of smiles by measuring facial muscle activities and facial surface transformation. We made it possible that the strength of the smile was fixed the same by using the biofeedback technique. And facial muscle activities that caused a change on skin surface were measured by surface electromyography and the physiological mechanism of the smile was examined. It became clear that the muscle activities of the risorius and depressor labii inferioris had a significant effect on the formation of the smiling faces. We confirmed that a change of the eye that is the symbol of the smile depended on the compression of the skin by the picture analysis of the face. The internal and external relations to make the characteristics of the smile were explained.
