An indicator of a genuine smile or true enjoyment. Smiles with Duchenne’s marker (i.e., the presence of orbicularis oculi activity) have been more often associated with the experience of positive emotions (e.g., amusement) in comparison with other forms of smiling.
Soussignan, R. (2002). Duchenne smile, emotional experience, and autonomic reactivity: A test of the facial feedback hypothesis. Emotion, 2(1), 52-74.