(Hadley Hooper for The Washington Post)

Q. I’ve been a full-time nanny for six years and have run out of potty-training ideas.

I care for three boys — a 6-year-old and a set of 3-year-old twins — but their parents can’t toilet train one of the twins and neither can I. Although he pees in the toilet, he waits as long as two to three days for the house to get real noisy and then he sneaks away and poops in his underpants. Apparently he hopes that no one will notice what he’s done, but then he quickly tells us about it because he wants to be changed right away.

I don’t know why he won’t use the potty. His parents have never punished him or treated him badly when he’s had an accident, and neither have I. We may act disappointed and say things like, “Oh, I wish you had used the toilet,” or “Ask me when you want to go,” or “What can I do to help you?” We’re very patient with him, too. We also give him rewards and bribes for using the potty, including favorite foods, new toys, a trip to the zoo — the usuals. He seems interested at first and says that he will try to use the potty, but he never tells us when he has to go.

Are there any tricks that might encourage him to use the potty?

A. You’re counting your calamities too soon. Very few children wear diapers to their senior prom.

In fact, most children are trained between the ages of 1 and 4, depending on the meshing of their bodies, their minds, their temperaments and maybe their birth order, too. The youngest child in a family often trains quickly, particularly if he’s a sanguine person who likes to imitate his older siblings. A firstborn usually won’t sit on the potty for quite a while; he’s too cautious for that.

A child may also be reluctant if he is a contrarian (or in a contrary stage) or if he thinks that he gets more attention for being bad than he gets for being good. Those aren’t the only reasons that it can take so long to train a child, however. A masterful block builder — the kind of child who cantilevers his Legos — may not go near the potty until he knows where his poop is going to go and exactly how it will get there. His friend, however, may not flush away his poop because he’d either feel like he was flushing away part of himself or worry that he could go down the drain, too. Young children find it hard to judge the size of anything, including themselves and the pipes in their house.

And then there are those children who simply refuse to use the potty — who knows why — and they won’t behave without a bribe. But please, make it a big bribe, like a classic tricycle, and only give it to him when he’s completely trained and out of pull-ups. Giving a piece of candy to a child each time he uses the potty is like giving him a dollar each time he does a chore or gets an A. The child who gets little rewards, bit by bit, will soon get tired of them and beg for bigger prizes.

There are better ways to toilet train a child.

Because this little boy is causing the problem, he should help you fix it. Have him dump this bowel movement into the toilet and flush it himself.

Then he should rub his underpants with soap, scrub them and rinse them in the basin and lay them out to dry. Although you’ll throw them in the washer later, these jobs will be interesting for the child; they will make him feel industrious; and, best of all, they will make him feel like a big boy. Once he makes that leap, he will want to use the potty, not because you tell him to use it, but because that’s what big boys do.

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