Very interesting.
I said to DS that I want to find a way for there to be less shouting in the house, and I'm reading about things that might help.
I gave him a cuddle, and mentioned the shoes incident and asked him about what he feels like when I ask him to do something. He said that when I ask him to do simple things, it makes him feel sick. He said it's not complicated things, only simple things. (That last bit was unprompted - I never suggested there could be any difference between simple tasks and complicated tasks).
I tried to ask questions as neutrally as possible, without putting ideas into his head as that wouldn't help at all! It was really interesting that he said simple instructions made him feel sick, could that be anxiety then?
I asked what I could do to make it better - how could I ask him to do things in a way that doesn't make him feel sick. He said he didn't know how to answer as he thought it might be a trick question. I reassured him it wasn't a trick question, but he didn't have an answer, I said that was OK.
I said, OK, how about we play opposites, Maybe if we know when it's worst, we can find the opposite and it might be the best? So, when does it make you feel most sick? And he said when I shout. I said, so how about I try to ask you really softly to do things, do you think that would help not make you feel sick? And he said, no, you already ask me softly. (But in reality I could ask more softly).
I gave him another cuddle and said we didn't need to talk about it any more right now but that I was still going to try to think of ways to stop the shouting.
Not long later he had to get dressed. I asked him, softly, to put his clothes on, he started getting distracted (picking up toys, avoiding going to his drawers etc). I asked him again to put his clothes on. He said he didn't like being asked, and that it made him feel bad. I said but if you put the clothes on, then it'll be over and done with, you won't feel bad then. He said, "but I still feel bad after".
I then changed tack and started doing something I used to do to good effect when he was little - turning it all into a game, so we pretended he was getting dressed to be in a running competition, and suddenly he wanted to and was dressed in no time.
Then a bit later, when I asked him to put his shoes on, he said he didn't want to because of "you know, what we talked about". I said "sweetheart, just because we talked about it doesn't mean you don't have to do it. You still need to do things like put your shoes on".
I think I'm going to take a step back and try to make more things a game, he loves fantasy. We used to do it when he was younger and I suppose I thought he was too old to be doing that all the time now, but if it helps, it's worth a shot I guess?