By contrast, if you were to smile spontaneously, in the presence of genuine emotion, you would not only flex your zygomatic but also tighten the orbicularis oculi, pars orbitalis, which is the muscle that encircles the eye. It is almost impossible to tighten the orbicularis oculi, pars orbitalis on demand, and it is equally difficult to stop it from tightening when we smile at something genuinely pleasurable. This kind of smile “does not obey the will,” Duchenne wrote. “Its absence unmasks the false friend.”
