Stall talk: The arcane rules of chit-chat that take place in the gents'

Royal flush: a scene from 'Powder Room'

Nearly 50 years after John Osborne and Arnold Wesker gave the world the kitchen-sink drama, a new dramatic form has entered the fray: the bathroom-sink drama.

Powder Room, a low-budget British film released today, is the first of the newly minted genre. Why? Because it has the notable distinction of being the first feature-length film to be set in its near entirety in a women's lavatory.

Based on a 2009 play by Rachael Hirons – entitled When Women Wee – the all-female film, led by Sheridan Smith and Kate Nash, promises to take us behind the door of the ladies', showing us the not-for-public-consumption interactions of six friends on a night out in a provincial nightclub. Which seems to mean: hugging, rowing, chatting, fighting, throwing up and taking drugs in unexpectedly large cubicles.

Having not really spent any significant amount of time in a female loo, I found myself watching the trailer and nodding along. It was a sort of confirmation. Of two things. Firstly, a-ha, I thought, so that is what they spend so much time doing in there – I knew the queue couldn't be that long. And then, in short order, I came to another conclusion: women are just so much more grown up and civilised than men.

On what do I base this conclusion? Well, approximately four times every working day I find myself in the gent's toilet at The Independent. Now, this is a compassionate, liberal-leaning newspaper staffed by people of wit and charm, but all that matters not one jot when you walk into the lavatory.

Just pushing open the door one feels an unmistakeable diminution of self. You become a schoolboy with tied tongue and you hope and pray that you don't see anyone you know. If you do, you nod or grunt; strike up a conversation and quite frankly you're sunk. You just end up coming across as a bit, well, weird. Much better to hide in the cubicle until you hear the door go and you know you can escape without saying hello to Larry in accounts. One doesn't want to behave like that but still these are the immutable rules of the men's lav. No one explains them to you, of course. You absorb them by osmosis and only extreme drunkenness can be used in mitigation for fracturing them.

How to explain this? Well, according to Phillip Hodson of the UK Council from Psychotherapy, when we walk into a lavatory we regress by a few millennia.

"Men become primitive: both suspicious and anxious. In that situation we are back as hunter gatherers and become preoccupied by both our place in the pecking order and also become worried sexually," he says.

The difference between the sexes on washroom etiquette can be traced back to birth, says consultant psychologist Ingrid Collins.

"When women are born, their first experience of another being is someone of the same gender and when they begin to individuate they do so within the same gender group" she says. The upshot: women can chat to each other while having a wee. Men, on the other hand, are much more likely to keep their mouths shut and their eyes looking only forward. This, says Ms Collins, is because soon after birth men become conscious that their mother is a different gender which can lead to feelings of isolation and loneliness.

"Men have to work harder at creating bonds. Groups of men tend to use rules and regulations as the glue of friendship. In a toilet with lots of random people there isn't much chance of that," she says.

In the absence of that loo rubric, men are left to flail. We repress ourselves monstrously and twist ourselves into the most frightful knots. I can quite confidently say that if you tried to make a film out of the classic male social encounter in a urinal it wouldn't last 90 seconds, let alone 90 minutes. When it comes to lavatories, men aren't just from Mars and women Venus – we are from whole different solar systems.