Why do we cry tears when we are emotional?

THAT'S THE WHY:If the eyes are the windows to the soul, tears surely give those panes a good wash so we can peer in.

They help keep the show lubricated, and we may start to produce more of them to help counter an irritation.

But the tears can also crank up and start spilling out of our lacrimal glands if we are highly emotional – and we humans seem to be unique among mammals in producing this kind of extreme blub in response to how we feel. Why is that?

One suggestion is that it could be a byproduct of the evolved changes in shape of the human head, while others point out that tears can alert others to our emotional state.

A 2009 study in Evolutionary Psychology showed that removing the tears from images of faces can change the viewer’s perception of the emotion being shown.

And it’s not just the sight of streaming tears that could be sending out messages – a study published in Science last January found that sniffing the tears of crying women appeared to suppress sexual arousal in men.

Research is now starting to reveal more of tears’ mystery components: a report just accepted this month in the Journal of Proteome Research screened samples of tears that lubricate the eye.

By effectively taking a snapshot of the biochemical payload relating to our metabolism, the approach identified about 60 compounds, most of which had not been reported in human tears before.