For a Q&A with Rose George, click here.

The flush toilet is a curious object. It is the default method of excreta disposal in most of the industrialized, technologically advanced world. It was invented either 500 or 2,000 years ago, depending on opinion. The ancient inhabitants of the mighty Indus Valley, in present-day Pakistan, had privies above channels of running water, whereas King Minos's palace on Crete, 4,000 years ago, fed rainwater through terra-cotta pipes to flush privies below. Toilet historians, of which there are few, attribute the modern flush toilet to Sir John Harington, godson of Queen Elizabeth I, who thought his godmother might like something that flushed away her excreta and devised the Ajax, a play on the Elizabethan word "jakes", meaning privy.

The golden age of the toilet, though, only occurred in the later years of the 18th century and the early years of the next, due to the trio of Alexander Cumming (who invented a valve mechanism), Joseph Bramah (a Yorkshireman who improved on Cumming's valve and made the best lavatories to be had for the next century), and Thomas Crapper (another Yorkshireman who did not invent the toilet but improved its parts). In engineering terms, the best invention was the siphonic ush, which pulls the water out of the bowl and into the pipe. For the user, the S-bend was the godsend, because the water that rested in the bend created a seal that prevented odor from emerging from the pipe. At the height of Victorian invention, patents for siphonic ushes were being requested at the rate of two dozen or so a year.

Nevertheless, although contemporary inventions like the telephone have gone through profound changes, the modern toilet would still be recognizable to Joseph Bramah. He could probably x it. And he most likely would be astonished that we haven't substantially improved it.

The modern toilet has probably added a decade to the human life span (and was voted the biggest medical advance of the last two centuries by the readers of the British Medical Journal). But it is flawed. Seating us high—the average American toilet now measures an astonishing 16.5 inches (42 centimeters) from rim to floor—it is ergonomically questionable, as it squeezes shut the colon and in fact hampers the process of evacuation that it is designed to aid. But the Western world is happy with it.

Marketers call toilets a "distress purchase," only replaced when necessary. One country treats the toilet differently: In Japan, the toilet is modified, improved on, innovated. It is a design object, a must-have, a desirable product. Enormous sums are spent on improving its smallest parts. Japanese toilets can, variously, check your blood pressure; play you music; wash and dry your anus and "front parts" by means of an in-toilet nozzle that sprays water and warm air; suck smelly ions from the air; switch on a light for you as you stumble into the bathroom at night; put the seat lid down for you (a function known as the "marriage-saver," and one that also prevents fine particles of fecal matter being sprayed around the bathroom with every flush); and flush away your excreta without requiring anything as old-fashioned as a tank. These devices are known as high-function toilets, but even the lowliest high-function toilet will have as standard an in-built bidet system, a heated seat, and some form of nifty control panel.

The Washlet, originally a brand name for a toilet seat with bidet function, has become a generic word for a high-function toilet (usually translated as Washeretto). Since 1980, TOTO, Japan's biggest and oldest toilet manufacturer, has sold 20 million Washlets to a nation of 160 million people. According to census figures, more Japanese households now have a Washlet than a computer.

It is easy—for anyone who has not used one—to dismiss a Washlet as yet another product of Japanese eccentricity: Robo-toilets. But the stunning success of the high-function toilet holds lessons for anyone—from public health officials to marketing experts—whose work involves understanding and changing human behaviour and decision making. It is instructive because only 60 years ago, Japan was a nation of squatting pit latrines. Today, the Japanese sit, use water and expect a heated seat as a matter of course. In less than a century, the Japanese toilet industry has achieved the equivalent of persuading a country that drove on the left in horse-drawn carriages to move to the right and, by the way, to drive a Ferrari instead.

I arrange to visit the TOTO Technical Center in Tokyo. It is a low, sleek building, oddly located on a residential street. The Center is described as "[a place] where architects come to get ideas about designs." Sample bathroom sets gleam in the distance; a row of toilets automatically lift their lids as I walk past, in a ceramic greeting ceremony. Photographs are forbidden. The toilet industry in Japan is a highly competitive business, and the top three—TOTO, Inax and Matsushita—keep their secrets close. My requests to visit TOTO's product development laboratories were politely refused.

The world's biggest toilet manufacturer was founded in 1917, when a man called Kazuchika Okura, then working for a ceramics company, thought it might be a good idea to manufacture toilet bowls. It was not the most obvious business plan in a nation that used squat latrines. Progress was slow at first. Then came World War II, which left Japan with a damaged infrastructure and a determination from planners to build superior housing connected to sewers. By 1977, more Japanese were sitting than squatting.

The new ceramic sitting toilet had disadvantages. Visiting an outhouse during Japan's freezing winters could never have been pleasant, but at least with a squat pan there was no contact between skin and cold material. The new style changed that: Now, flesh had to sit on icy ceramic for several months of the year, a situation worsened by a national resistance to central heating that persists today.

TOTO spotted a flawed design that could use some innovation. In 1964 the Wash Air Seat arrived in Japan. Produced by the American Bidet Company, this detachable seat featured a nozzle that sprayed warm water and also blew hot air for drying purposes. In the U.S., the Wash Air Seat had been aimed at patients who had difficulty using toilet paper or reaching round to wipe themselves. It was a niche item that TOTO thought had mass appeal. After all, water is better for cleansing, something that cultures who wash rather than wipe know well. For water cultures, using toilet paper to clean the dirtiest part of the body makes as much hygienic sense as rubbing oneself with a towel instead of taking a shower.

But TOTO's version failed. It was too expensive. The bidet function was too foreign. And Japanese also didn't know they wanted better toilets. The privy was neither talked about nor acknowledged, a cultural convention demonstrated by the common proverb Kusaimono ni futa wo suru (to keep a lid on stinky things). The toilet could not be advertised. So the Washlet languished in obscurity for years.

At TOTO I am joined by Ryosuke Hayashi, a senior engineer and important man. Of the 1,500 patents that TOTO has filed in Japan (and 600 internationally), the Restroom Department is responsible for half. Rick finds my interest in the Washlet quaint. I say that for any non-Japanese person used to a cold, ceramic toilet that does nothing but flush, the Washlet is extraordinary. He's unconvinced.

He'd rather talk about the Neorest, TOTO's top of the line toilet and, in his engineering eyes, an infinitely superior combination of plumbing and computing. Certainly, the Neorest looks gorgeous. It should, when it retails in Japan for $1,700, and in the U.S. for $5,000. Rick thinks that the price is a bargain, considering that "it has a brain." The Neorest takes two days to learn its owner's habits, and adjusts its heating and water use accordingly. It knows when to switch the heat off and which temperature is preferable. It has sensors to assess when the lid needs to be put down or when the customer has finished and the nozzle can be retracted.

All this technology has come from years of research, billions of yen and many great minds (TOTO has 1,500 engineers)—and a visit to a strip club. I persist in asking about the genesis of the Washlet and how it changed Japan, and Rick finally humors me. To sell the Washlet to an unwelcoming public, it had to work properly. The Wash Air Seat and the early Washlet operated mechanically. It took several minutes for the spray to spray and for the water to heat. TOTO solved this by making the workings electronically operated, the spray instant, and the angle perfect. The Washlet nozzle extends and retracts at exactly 43 degrees, a position precisely calibrated to prevent any cleansing water from falling back on the nozzle after doing its job. (This is known as "backwash".) Determining the angle was a long, careful process, Rick says. I ask him how the research was done. He says, "Well, we have 20,000 employees," and stops. I wait for enlightenment.

The answer lies in a comic book. This is a 48-page TOTO history published by Weekly Sankei magazine in 1985, five years after the company had relaunched the Washlet. Its heroes are Mr Kawakami, a TOTO engineer, and his portly, cheery colleague, Mr. Ito. Kawakami and Ito are entrusted with improving the Washlet. The nozzle has to be accurate, and to make it so, they need to know the average location of the human anus. Facts like this are not easy to find, so they turn to the only source material available, which is anybody on the company payroll. Their workmates aren't impressed. "Though we are colleagues," one says with politeness, "I don't want you to know my anus position."

But Kawakami and Ito eventually prevail. Three hundred colleagues were persuaded to sit on a toilet—in private—and to mark the positions of their anuses by fixing a small piece of a paper to a wire strung across the seat. The average is calculated (for males, it comes to between 27 and 28 centimeters, or 10.5 and 11 inches, from the front of the toilet seat), but that's only the first hurdle. Mr Kawakami is now tasked with improving the Washlet's ability to wash "the female place". He needs to know how many centimeters separate a female's two places, and is initially at a loss. Obviously the best place to research female places is in a place with females, preferably naked ones. That's where the strip club comes in, though most strip club clientele are unlikely to react as Mr. Kawakami does, by shouting, "Three centimeters!"

By 1995, 23 per cent of Japanese houses had some kind of Washlet, according to a Cabinet Office survey, and by the end of the next decade, the figure had doubled. The obvious business plan was to go global. In toilet terms, the wealthy consumers of the United States are the next frontier. TOTO opened its first U.S. office in 1989. Its current premises in New York City are in downtown SoHo, where the window display—a glossy, sleek Neorest—somehow fits in well on this street of designer shops.

TOTO's initial success in the U.S., though, had nothing to do with aesthetics. In 1992, after it was noted that a flush toilet uses 40 percent of a household's water, the United States government passed the Energy Policy Act (EPAct), requiring all new toilets within two years to use only 1.5 gallons (5.5 liters) for each flush, when the average was an astonishing eight gallons (30 liters). The toilet industry was wrong-footed. Two years was barely enough time to change production lines, let alone reconfigure a toilet design that relied on a set volume of water to function. Consequently, the next several years are still known as the time of clogging.

American manufacturers' loss was initially TOTO's gain. TOTO's success in Japan had come through clever advertising and marketing, but it was also due to a brown, gloopy material called gi ji obutse, which translates as "fake body waste". It is, TOTO staff in Japan tell me, "a key part of TOTO," and so key, the recipe is top secret, though they will reveal that it involves soybean paste.

Soybean paste (miso) is a lethal weapon in the battle for toilet market victory, because toilet-makers need to test ushes, and they need test media to do it with. A ush is a chaotic event. Various media bounce around trying to get through one small opening. The more realistic the test media, the closer its properties—buoyancy, density—to human feces, the better the ush. Toilet engineers have always known this: When George Jennings's Pedestal Vase won a gold medal at a Health Exhibition in 1884, it had successfully ushed 10 apples, one at sponge, three "air vessels" (crumpled paper) as well as cleaning the "plumber's smudge" smeared on the bowl's surface.

When the National Association of Home Builders (NAHB) published a survey in 2002 testing toilets for ush performance, TOTO models were ranked rst, second and third. This helped TOTO's reputation and sales: Since 2003, annual U.S. sales have doubled (from 14.4 billion to 30.1 billion yen, or $257 million). TOTO won't release sales gures—beyond saying unhelpfully that the company is "the recognized leader in the toilet category," which would puzzle industry leader Kohler—but, at least temporarily, gi ji obutse helped to give them the ushing edge in a clogged nation.

Also, TOTO had successfully sold its toilets on the concept that they could keep the consumer clean, rather than the other way round. It would do the same in America. In 2007 the expensive "Clean is Happy" campaign was introduced to the American public. There were viral Internet ads and a lavish Web site featuring disturbingly cheery people telling you what Washlets could do in language Americans could understand. The deodorizer, one cheery person explained, "is kind of like the catalytic converter in your car." It is "a hands-free clean," said another. It uses water, and what's so scary about that, when "we wash our faces and hair with water! Humans love water!" It will be a hard sell in a county that still associates bidets with louche behavior and Parisian debauchery. Anal washing still means dirty naughtiness, as many Muslim-Americans revealed in a 2005 show called Lota Stories, where Americans recorded their experiences of using a lota—a cupful of water—in their toilet habits. One contributor left some useful advice gained from several years of trying to use water in a culture content with "the complex, ridiculous thrones" (as described by philosopher Alan Watts) and unsatisfactory paper-cleaning methods. Keep a plant in the bathroom, the contributor wrote, to explain away the watering can or cup. Above all, use discretion. "Ignore the impulse to explain what you are doing, even to friends. Unless people have been using a lota all their lives, the benets completely escape them, and they will view you as a freak with a freakish bathroom custom."

TOTO won't admit sales figures, but its American reach is nothing like back home. Perhaps the robo-toilet revolution is simply taking its time. But Tomohiko Satou of TOTO's archrival Inax is noticeably lacking in TOTO-style optimism. He spent time posted in Inax's San Francisco office, where sales, he admits, were "not so much." "Japanese people," he tells me, "understand that our product is very sanitary and clean." But years of trying to explain that to Americans taught him a painful truth. "Americans just don't want to use it. They're not scared. They're just not interested."