“Child does not wear nappies during the day or night. When they want to pee/poop, they ask for a nappy.
Parent has offered the toilet/potty intermittently, and occasionally talks about how "I go in the toilet... Grandma goes in the toilet... Nathan [who you completely hero worship] goes in the toilet..."
Idea of child going in the toilet/potty is met with horror.
Underwear, either just like parental ones, or with favourite cartoon characters, are rejected with disgust.
We want to avoid bribery. We certainly don't want to force child to sit on loo/potty (even assuming we could do the necessary gymnastics)
Any splendid ideas not involving bribery or forcing? It's certainly a psychological barrier rather than a physiological one.”
What is horrible about going in the toilet/potty? I think that seems like the important question to answer.
Splendid ideas not involving bribery or forcing would really hinge on what is unappealing about the toilet/potty. I think diapers are obviously unappealing… It’s pretty nasty to have poop smushed on your skin. Lovely to avoid that mess. Lovely to just flush the yucky stuff away. Lovely to be clean and dry. If I understand the situation, then this particular child already appreciates how comfortable it is to NOT wear a diaper, since diapers are requested when pee/poop is on the way, and not worn all the time. Perhaps it would be helpful to point out, explicitly, that using toilets enables one to totally skip that yucky feeling?
Maybe it’s mobility? Diapers enable people to go wherever they want without soiling anything. Portable potties can be similarly useful – you can have one in each room, and they can be used to scoot around on hardwood floors. Connected to mobility is how very boring bathrooms can be… Perhaps a few drop of red food coloring in the toilet so that pee turns the water orange? Or blue to make green? A hand held video game? Digital camera handy to document the varied shapes of the poop logs before they get flushed? And, of course, good books or magazines are a classic… Toilet paper with little flowers or hearts or teddy bears or whatnot? Step stools, smaller toilet seats, fun soap for handwashing… Taro Gomi’s book, Everyone Poops, is a fun read.
Maybe it’s the idea that giving up diapers means giving up babyhood? Even if parents never say this explicitly, it’s a concept that appears in many, many, many books and shows made for children. It’s also often implicit in lists of who uses the toilet and who doesn’t… Of course, in the eyes of a parent, any child will always be loved and cherished. Sometimes stating this explicitly helps. Just remember to really relish and enjoy the current moment. Whatever happens, however the diapers are ditched, they will eventually be ditched. So love the person. Might also be interesting to put it out there that many, many people end up in diapers again in old age. Check out the adult diaper section… Joke about the prospect of the child changing the parents’ diapers in years to come… It's also worth noting that some babies never wear diapers. Parent could offer to hold the child over the toilet the way that families practicing elimination communication in our culture do. It might be interesting to see pictures of tiny babies without diapers. Basically, separate babyhood from diapers.
Or maybe it’s a direct reaction to emotional undercurrents in the family? "This is important to other people, but I get to decide what I do with my body, thank you very much." If this is the case, then backing way, way, way off seems important. No matter what, no matter when, eventually the diapers will be ditched. And the truth is, the child is in control of this. Parents can offer information and support, or they can push and prod, or they can do a little of everything, but ultimately, the child is in control.
Or maybe it’s about ritual – diapers have become a ritual? Would it be fun to lay a diaper in the potty – not on the child’s body, the diaper is still catching the pee and poop, but the pee and poop is not trapped against the skin? This could be a way to see how potties and toilets are actually more comfortable without totally ditching the diaper ritual. A transition, if you will?
Well, there you have it -- lot of thoughts, some goofy, some serious. As always, I hope something here helps you find a solution. Honestly, I hope that in the time it took me to craft my reply you’ve already found a way forward together.