Tearing: Breakthrough in human emotional signaling

From the book : Evolutionary Psychology 7 issue 1 : 52-56.
Tearing is not a benign secretory correlate of sadness or other emotional state, but a potent visual cue that adds meaning to human facial expression, the tear effect.
Although tearing (lacrimation) provides ocular lubrication and is a response to irritation in many animals, emotional tearing may be unique to humans and does not develop until several months after birth.
This study provides the first experimental demonstration that tears are a visual signal of sadness by contrasting the perceived sadness of human facial images with tears against copies of those images that had the tears digitally removed.
Tear removal produced faces rated as less sad.
Anecdotal findings suggest further that tear- removal often produced faces of uncertain emotional valence, perhaps awe, concern, or puzzlement, not just less sad.
Tearing signaled sadness and resolved ambiguity.
The evolution and development of emotional tearing in humans provide a novel, potent and neglected channel of affective communication.