Contagious lawning is a sign of empathy, and it turns out that chimpanzees sympathy-yawn too. More, they do so with familiar chimpanzees, but not with strangers.
Are there any literary examples of sympathy-yawning? If so, are there examples of characters who do not participate? It would seem to me that non-participation in sympathy-yawning would be very telling of a character or characters -- whether they are non-sympathetic, or the one yawning is a stranger.