Back to the tear ducts, for example. “There are several studies over the years that have shown that men have larger tear ducts in their eyes, so that it is less likely for the tears to well up to the point of spilling over the eyelid onto the cheek,” said Dr. Geoffrey Goodfellow, an associate professor at the Illinois College of Optometry in Chicago. There’s also this paper from the 1960s, in which a physician from the University of Michigan reports how he used male and female skulls to measure the length and depth of tear ducts, finding that women’s were shorter and shallower.
Hormones also may provide an explanation, too, including testosterone, which, Vingerhoets believes, inhibits crying. Male prostate cancer patients, for example, tend to become more emotional when treated with medications that lower their testosterone levels. But this isn’t just about testosterone: Back in the 1980s, biochemist William H. Frey and his team analyzed the chemical makeup of emotional tears and compared them to tears caused by irritants. They found, among other things, that emotional tears tend to contain prolactin, a hormone produced by the pituitary gland that is associated with emotion. Vingerhoets passed on a 2012 paper from a team of Nigerian scientists that he said may help connect this to the gender difference in crying.
From the paper:
[A]dult women have serum prolactin levels almost sixty percent above the average male. This difference may help to explain why women as a whole cry more frequently … . Before puberty, the serum prolactin levels are the same in both sexes, and studies have found that the crying level of boys and girls is much more similar before puberty.
--Melissa Dahl, New York, on the biology of crying