When Middle Son was very young, around 20 months, we began to be concerned about him. He didn't respond at all to his name. The first thing that we did was have his hearing tested. When the hearing tests came back positive, we moved on to other tests which eventually led to the diagnosis of autism.
Now we knew that he could hear, but he still didn't listen.
When he was about 2 1/2, he started climbing up on the kitchen counter. His favorite thing to do was stand on the lip of the sink and jump up and down. This was very alarming. The lip of the sink is a very small surface, it's often wet, and it put Middle an entire body length above the floor. I was afraid that he would fall and hurt himself.
MomC and I would tell him to get down and he ignored us. So I decided to devote some serious effort to the problem. I stood at the kitchen counter with a magazine. Every time Middle climbed up on the counter I would say "no Middle, get down." I would pick him up and put him back on the floor. Then I would read my magazine for a few minutes until he climbed back up on the counter and we'd repeat the process.
After a couple of weeks of this, when I would tell Middle to get down he actually got down. It was a huge breakthrough. By this team we were working with speech therapists, behavior therapists, and lots of other professionals. One of the things I learned from them was the utter necessity of consistent behavior with Middle. In a lot of ways it reminds me of training a dog. I don't like the analogy--Middle is a human being, not a dog--but it conveys information well, so I use it. When you are training a dog, they tell you to always make the dog obey a command; communicate to them that disobedience is not an option. If you tell him to sit and he doesn't, kick his back feet out from under him so that he falls on his butt. Then say "good sit."
So I took get care about when and how I asked Middle to do things. I gave very simple, clear, one-step instructions. Rather than saying "put your coat away," I would say "come here" and wait for him to comply, "pick up your coat" and wait, "go over there" and wait, then finally "hang your coat on the hook." If at any step he didn't do what I asked, I would go to him, take his hand, and physically take him where I had told him to go. Eventually Middle concluded that if I told him to do something he was going to end up doing it, so he might as well do it now rather than wait for me to come get him.
MomC never made that investment. She finds it very difficult to get him to listen. She complains that he ignores her. I've seen him do it. More than once when I've arrived at her house to pick up the boys, Middle has been out in the back yard. She calls for him to come in and he ignores her. She calls 2, 3, half-a-dozen times, and it's like he doesn't even hear her. Sometimes I want to yell at her to get her rear end out there and make him come inside. As long as she tolerates him ignoring her he will continue to do so. Then I call out to him to come get in the car to go to my house. He immediately comes inside. MomC glares at me and says "that is soo frustrating."
I taught Middle to listen to me. She never taught him to listen to her.