Duchenne smile
n.— «He knows the difference between Duchenne and non-Duchenne smiles: one crinkles the orbicularis oculi muscles and the other does not. One is genuine and shows in the eyes; the other mostly involves the mouth and looks merely polite. Mr. Keltner has made sure that his smile falls on the right side of that distinction, and that it’s Duchenne all the way.» —“Smiley Faces in Our Chromosomes” by Janet Maslin New York Times Jan. 19, 2009. (source: Double-Tongued Dictionary)
Further reading
Understanding the varieties of conversational styles can mean the difference between feeling you’re understood and being insulted. “High-involvement” speakers interrupt or talk along with someone else to signal their enthusiasm...