Rodent tears contain a chemical signal that reduces aggression in conspecifics. This study shows that human tears similarly contain a chemical signal that, although odorless, activates human olfactory receptors in vitro, alters neural activity in an olfaction-aggression brain network, and lowers male aggressive behavior.
I wonder whether female tears also influence females, and if yes, how. And what about male tears? In rodents, they carry a signal too. And what about the real experts on crying - children?