potty-training Chinese toddlers often wear split pants, so that they can be held out to relieve themselves on to the ground without soiling their clothes. In the West, however, babies wear nappies or diapers until they learn to use a pot. For many parents, the learning process becomes a battleground.

There are three probable reasons why young babies cannot learn to use pots. First, their sensory nerves (or the interpretation of their signals by the brain) are not well enough developed for them to know when they have excreted, let alone when they are ready to do so. Second, they do not know how to control their sphincters; so they can't perform on cue. Third, even though the thought of a wet or dirty nappy is horrible to the parents, most babies do not mind it at all.

Some parents try desperately to potty-train their children much too young, and may think not only that they have succeeded, but also that they, the parents, have made a great achievement. But then at the age of 3 or even 4 the children suddenly realize they have a wonderful weapon at their disposal, and start performing at the most inconvenient moments — in the supermarket, for example, or in the middle of lunch with Grandma…

A 1989 survey in Minneapolis reported that three-quarters of parents started potty-training when the child itself was apparently ready; 30.5% between 18 and 23 months, 42.6% aged between 24 and 29 months. The average age for completion was between 24 and 27 months.

Advice to mothers has gradually softened during the last two centuries. Pye Henry Chavasse suggested in 1839 that the baby should be held out over a pot at least a dozen times a day at 3 months old; if this were done, there need be no more nappies at 4 months!

Around the turn of the century, the now less-influential Sigmund Freud regarded sphincter control as part of the second, or ‘anal’ phase of development, and Freudians suggest that babies become aware that what they produce is theirs, comes out of their bodies and is part of them. Therefore it does not belong to the mother, and should not necessarily be given to her, let alone thrown away in the lavatory. Since then, psychoanalysts have suggested that much of our behaviour stems from the way we were toilet trained. To take just one example, a 1992 paper suggested that François Mittérand's toilet training accounted for his stiffness, obstinacy, shyness, anxiety, attitudes towards money and time, ambivalence, hesitations, contradictions, and desire for power.

In 1912 Edward Mansfield Brockbank said that ‘After the second month, the baby can be held … in a sitting position, with some weight on the chamber. … It should be put on the chamber before, during, and after each meal…’

In 1939 Marie Stopes wrote, ‘When a baby has responded to the touch of the chamber and passed either water or a motion, he should be rewarded by an expression of pleasure by nurse or mother. “That's right. Good baby” … On the other hand it is a cruel mistake to show signs of displeasure or annoyance about wet or soiled nappies.’

Many clever devices are available to help anxious mothers and encourage the babies, including a musical potty, marketed with the slogan ‘Make toilet-training fast, easy, and fun!’. When gold-plated sensors register moisture they trigger one of sixteen cheerful tunes, including Yankee Doodle, Little Brown Jug, and Chim-Chim-Cheree.

Adam Hart-Davis