Video of Bat Kid in San Francisco; a romcom; the heating was broken two weeks ago when it snowed. These are just some of the answers to the question "why did you last cry?" in a recent poll I did of about 60 friends and acquaintances.

The first two reasons came from men, and perhaps they back up the assertion that men are more likely to cry out of empathy or over a failed relationship, whereas women cry when they feel inadequate, are confronted by difficult situations or when they remember past events. So says a study by the German Society of Ophthalmology from 2009.

Until recent decades, studies of emotional crying in humans were few and far between. Even Charles Darwin, that arbiter of human behaviour, dismissed weeping as "an incidental result, as purposeless as the secretion of tears from a blow outside the eye or as a sneeze from the retina being affected by a bright light". If only it were that simple.

In an effort to understand this most unique of human behaviours – for we are the only species that sheds emotional tears – the Dutch researcher Ad Vingerhoets, in his book Why Only Humans Weep , raises the spectre of a tearless world and asks: "What would the consequences be for mankind and society?"

For anyone suffering from Oscar fatigue – okay, okay, we might have had something in our eye during Lupita Nyong’o’s acceptance speech – a world without weeping might sound like a utopian dream come true, but there’s more to the sob story than you might think.

Tears, says Vingerhoets, in particular those we shed in the presence of others, have huge cultural and social importance, as well as their biological function, and our crying is “the result of an interaction of psychobiological, cognitive, emotional and sociocultural processes”.

In a tome densely packed with the latest research on weeping, Vingerhoets explains why tears have developed as the solution to the problems and challenges of our ancestors, from infants eliciting care and protection to adults seeking to bond and reduce aggression. “These functions,” he suggests, “also explain why crying is a behaviour that occurs most frequently in children and women, who may lack the strength and power.”

The ancient Egyptians believed that tears originated from the heart, while in the Old Testament it is written that tears result from a weakening of the firm substance of the heart, which turns into water.

This “cardiocentric” theory of the origin of tears persisted with Aristotle. Even Leonardo da Vinci, whose drawings of the human anatomy are mostly accurate down to the smallest detail, believed that tears welled up from the heart to the eyes, in tubes that passed from the tear ducts straight to the heart, passing through the canal of the nose.

The Danish scholar Niels Stensen (also known as Nicolaus Steno) discovered the lachrymal gland in 1662 and, by the end of the 17th century, a valid anatomical conception of the entire lachrymal system, including the lachrymal duct, was widely available.

The benefits of female tears
While some theories posit a scenario in which men evolved the ability not to cry, others instead suggest that women developed the capacity for tearful crying because of its benefits. Vingerhoets quotes a 2006 study that suggests "female crying acts as a signal to alert males during a conflict that they have overstepped boundaries and it thus prevents conflict escalation and reduces aggression". Tears have also been shown to help social bonding among women, but does this function translate to the workplace?

Sheryl Sandberg certainly thinks so. Facebook's chief operating officer and the author of Lean In encourages the odd weep in the workplace. In a speech to graduating students at Harvard Business School, she said: "I've cried at work . . . And it's been reported in the press that Sheryl Sandberg cried on Mark Zuckerberg's shoulder, which is not exactly what happened."

Rather, Sandberg tries to be herself, to be “honest about my strengths and weaknesses, and I encourage others to do the same. It is all professional and it is all personal, all at the very same time. I talk a lot about bringing your whole self to work – something I believe in deeply.”

She officially became a billionaire at the beginning of this year, but it is only recently that she “started speaking up about the challenges women face in the workforce”.

The message seems to be filtering down.

A Dublin-based employee at one of those mega multinational communications corporations we hear so much about – let’s call it “Twaceboogle” – says: “One of the downsides I see to our work culture is that people are encouraged to throw everything at their job and we hire over-achievers who put huge pressure on themselves. Sometimes this results in a pressure cooker of stress when people can’t step back from their jobs.

“I’ve definitely done this in the past, and have cried at least three times at my current job. All three times I was stressed out to the max.”

It’s not always a bad thing, however, says the thirtysomething team leader, who wishes to remain anonymous. “I really understood in a different way this year what Sheryl Sandberg means by bringing your whole self to work. I was holding back a lot of what was happening outside of work and was finding it increasingly difficult to do my job well. My team could sense this, but interpreted it as me being distant and not engaged.

“I realised that I had to let people know that I was going through a rough time, even though I didn’t want to say why. This type of relationship is becoming more expected in work cultures and I think it’s particularly important for managing millennials, who are a lot more emotional and have less of a barrier between work and home.”

Mere mortals
But what about those of us who don't work at a forward-thinking frontier like Twaceboogle – us mere mortals who are still confined to a silent sob over the cistern if our eyeballs spring a leak?

Encouraging as it is to hear the likes of Sandberg making corporate virtues of feminine qualities, she acknowledges her rise up the ranks was a different story. “I never told anyone I was a girl . . . I left the lights on when I went home to do something for my kids. I locked my office door and pumped milk for my babies while I was on conference calls.”

Eve Ensler has a theory about this suppression of our "inner girl", as she calls it. The author of The Vagina Monologues and creator of V-Day, a global activist movement to end violence against women and girls, maintains "the whole world has essentially been brought up not to be a girl".

In a Ted talk, filmed in India a couple of years ago, Ensler says: "To be a boy really means not to be a girl. To be a man means not to be a girl. To be a woman means not to be a girl. To be strong means not to be a girl. To be a leader means not to be a girl."

Associating this “inner girl” with emotions and empathy and compassion, Ensler says we have systematically annihilated it – in men as well as women. And why? Because, she says, “feelings get in the way of empire-building”.

Indeed, an Israeli study in 2011, published in the journal Science , found that female tears contain a chemical that may reduce testosterone levels in men. Could it be that crying is nature's way of toning down the testosterone – and the associated aggression – in the room? And would that be such a bad thing in the workplace?

If women's tears have evolved as what Vingerhoets terms a "weapon of the weak", maybe it's time to make like Sheryl Sandberg and start crying all the way to the bank. That doesn't mean advocating "crocodile tears" or bawling on demand, but rather ditching long-held notion that big girls – and boys – don't cry. Ever.


THE CRYING GAME: DIFFERENCES BETWEEN WOMEN AND MEN

According to a study by the German Society of Ophthalmology, women shed tears on average 30- 64 times a year, whereas men cry just six to 17 times during the same period.

Men tend to cry for two to four minutes, the study found. Women cry for about six minutes and weeping turns into full-blown sobbing in 65 per cent of cases, compared with 6 per cent for males.

Women cry when they feel inadequate, when they are confronted by situations that are difficult to resolve or when they remember past events. Men, meanwhile, tend to cry from empathy or when a relationship fails.

Another study in Britain in 2004 showed that not only were there differences between genders when it came to crying, but also regional differences. For exam- ple, the break-up of a relationship and an argument with a partner both elicit more crying in London (47 per cent of women and 31 per cent of men) than in Scotland (33 per cent and 15 per cent). On the other hand, men in Scotland are found to be more likely to cry at the birth of a baby and at weddings than men in London.