Specifically, the presence of a double or bifid zygomaticus major muscle may explain the formation of cheek dimples.

The zygomaticus major muscle is responsible for pulling the corners of the mouth back when you smile, and therefore is the muscle used to test for positive emotional response.

Research with psychophysiological methods corroborated this positive effect on affective experience: easy-to-perceive stimuli were not only judged more positively but increased activation in the zygomaticus major muscle, the so-called "smiling muscle".

It primarily focuses on two major muscle groups in the face, the corrugator supercilli group which is associated with frowning and the zygomaticus major muscle group which is associated with smiling.