KEY POINTS:
It's as natural as breathing, as falling asleep. We do it, if we're lucky and healthy, about six to eight times a day. But our toileting habits, and hang-ups, are banished from polite conversation to school playgrounds, blokey pub talk and leery girls' nights out, their public airing cloaked in toilet humour.
Yet, once you get past the cringing, experts say toilets - especially our behaviour in public toilets - reveal much about our inner selves.
We all know toilets are handy sites for other activities, such as skivving or stealing quiet time with the paper. In a recent Australian survey, 53 per cent of men and 39 per cent of women took magazines or newspapers to the loo with them. Crosswords and daydreaming were also mentioned.
And, rather disconcertingly, 11 per cent of respondents admitted to having used a mobile phone while otherwise engaged.
The Herald on Sunday's own informal survey turned up other forms of multi-tasking - including using a laptop and, ugh, eating. Then there are the furtive sexual encounters and taking of illicit substances, although fewer will admit to these.
The Aussie survey also asked if people would be comfortable relieving themselves in front of partners - a surprising 60 per cent said they were. But when it comes to public settings, embarrassment and concealment rule.
Ally McBeal and her colleagues may launch into impromptu Barry White numbers by the basins, but the rest of us tend to keep things as low key as possible. Our survey found an array of strategies to mask tell-tale sounds and smells in office and other public toilets, many involving carefully placed toilet paper and perfectly timed flushing. Many simply avoided passing bowel movements outside of home.
Urinals confront men with vast potential for social humiliation, as well as blokey bonding, sometimes at the same time. Ruth Barcan, a gender studies lecturer at University of Sydney, interviewed men about using public toilets. They described the competitive peeing games played by school boys and drunken men - "sword fights", seeing who can pee the highest or hit the "trough lolly" (urinal cake).
The tongue-in-cheek symbolism is obvious. As an online lads' mag puts it when describing the game "Blast Off", the winner is "letting you know his stream is more powerful than yours, hence he is the superior male".
Not surprisingly, men also mentioned urinal "stage fright" - seizing up in front of others. Writes Barcan: "The design of the urinal throws down a gauntlet to users; 'are you man enough?' it seems to ask."
Beyond their sanitary function, she argues, men's public toilets are "filled with anxiety and rules", places where heterosexual masculinity is defined, tested and policed.
There are even internet "urinal games" that test your knowledge of correct urinal etiquette. Apparently, when faced with three urinals, all empty, you go to the one farthermost from the door. If someone's already taken that one, you go to the one closest to the door because it's farthermost from him. If only the middle one is free, the safest thing is to wait. And, at all times, keep your eyes straight ahead.
Confirms one of our male respondents: "Guys should never look or stand too close or say things like 'So this is where the big nobs hang out!' (A favourite joke of my dad's)."
A contender for the most excruciating movie moment must surely be the scene in Trainspotting when Ewan McGregor's character dives into "the dirtiest toilet in Scotland" to retrieve the drug he accidentally released into the scum-coated bowl.
The scene taps our deep collective disgust at toilets and what happens there. There's more to this than an evolved response to substances that could make us sick.
Barcan observes our "fetish for the appearance of hygiene" - the urinal cakes, the air fresheners that make things seem clean but have little hygienic power. In fact, a British study found more bacteria on the mobile phones it tested than the toilet seats.
Our desire for this semblance of hygiene, she argues, is to do with the crossing of boundaries that give us a sense of order but are often flimsier than we like to admit.
Like the boundary between humans and animals.
Observes one of our survey respondents, "We like to say we are humans, and sophisticated, intriguing creatures, but we are animals. We laugh at toilet humour because it is kind of embarrassing - it reminds us of who we really are. It also connects us, I mean even the Queen farts."
A challenge to the boundary between private and public at public toilets helps explain why public toilets can cause so much discomfort.
Not only may your most private activities be heard or smelt by strangers, others have sat on that seat, fingered the same flush button.
Almost all our respondents reported wiping seats or hovering above them; one woman said she prefers to "drip dry" rather than touching a toilet paper dispenser.
Waikato University human geographer Robyn Longhurst points to another, fundamental boundary crossed at the loo - the body's boundary. "When the body breaks its boundaries in any way there are social taboos around that.
"Where we break the body's boundaries are sites of vulnerability, so there's always rituals around them."
Toilet humour - like a lot of humour - derives its humour from our squirming.
"We tend to joke about things we're uncomfortable about."
There was a lot of joking around in the interviews Longhurst conducted with 18 (straight) men about using the bathroom. "Bodily fluids are often associated with femininity rather than masculinity, so men feel especially uncomfortable talking about their bodily fluids."
When it came to solids, however, Longhurst discovered the men had a "whole vocabulary I was unaware of".
But while it breaks some dearly held boundaries, toileting reinforces others. Separate men's and women's loos reinforce the gender boundary.
And although toileting can be seen as a social leveller, class and cultural differences are clearly still at play.
Some workplaces have different toilets for management.
And, it's been speculated, using the word "toilet" instead of "loo" was among a series of middle-class-betraying gaffes with which the mother of Kate Middleton, Prince William's one-time girlfriend, flushed her royal aspirations for her daughter down the proverbial.
Loo Lowdown
The average person goes to the toilet 2500 times a year and spends some three years of his or her life in the loo.
The Singapore-based World Toilet Organisation, www.worldtoilet.org, established in 2001, is part of an international movement for improved public sanitation. It organises the annual World Toilet Summit and Expo and has declared November 19 "World Toilet Day". Its 10 tips on toilet etiquette include wiping the seat before and after and not taking too long.
The Sulabh International Toilet Museum in India has latrine exhibits dating back to 2500BC.
This year, Japan's second biggest toilet maker admitted its automatic bidet-model lavatories are prone to overheating and catching fire.
The Chinese city of Chongqing is hoping its new state-run, four-storey block will earn a Guinness world record for the biggest block. The structure contains more than 1000 loos and themed "sculpted" urinals.
Around 40 per cent of the world's population doesn't have clean sanitation.
At least four million Britons are affected by toilet phobia, according to Britain's National Phobics Society. Paruresis, or shy bladder syndrome, is the fear of urinating in the company of others, while parcopresis is bashful bowel syndrome.
Sigmund Freud believed our toilet-training experiences shaped our personalities. Too lenient an approach fosters a messy, wasteful and destructive "anal-expulsive personality". Training that's too strict or too early encourages a stringent, orderly and obsessive "anal retentive personality".
