My daughter lies on the floor, waving her legs around so I can't get her tights on. She can't do it herself; her legs are broken. This one needs to be amputated. It hurts right here. She's too tired and floppity. I catch one kicking foot, but she's off, she just needs to check something in her game. She is always playing some imaginary game or another, usually 'being' some character of her own invention. The tights have to go on before it's time for preschool, so I get up and follow after her. This is demand avoidance in action, and it goes on *all*day*long* in our house. But this isn't my PDA child.
This isn't just learned behaviour, either. Some of it undoubtedly is, but for the most part the tactics are not the same as her older sister's, and nor are the triggers. This is a child with a more typical, and milder, presentation of ASC (autism spectrum condition) traits. And the demand avoidance is part of that.
So how do I know she doesn't have PDA? She spends a lot of time and energy avoiding demands, and a lot of time engaged in imaginative role play. Several people have mentioned that she acts a lot like their suspected-PDA pre-schoolers, some have questioned whether she might just have a milder presentation than her sister. I could be wrong, but I still maintain that it is a typical presentation of mild ASC traits in a four-year-old girl.
The demand avoidance is natural. She is busy with her own happy little world, and doesn't want to be interfered with and made to conform to another person's agenda. Perfectly normal for a child with Asperger's or even maybe ADHD, or maybe just a strong will, deep imagination, and some mild autistic tendencies. What this behaviour lacks, when compared to my PDA child, is the pathological aspect to the demand avoidance, the obsessive feel to the behaviour.
With child number 2, if I keep pushing and hold firmly but gently to the boundaries, it may take a while, but she will eventually comply. With my PDA child, any attempt to push toward compliance will inevitably escalate to an explosion. It might happen either sooner or later, depending on demand tolerance at that particular point in time, but she will explode. Not out of temper or defiance, but out of desperation. She needs to avoid demands placed on her. She avoids them like a wild colt avoiding rough attempts at 'breaking in'. Like being made to put socks on is a life or death situation. Pushing her will break her and she will explode in a wild attempt at self-preservation.
And that, in essence, at least as far as my experience with two very different children, is the difference between just plain demand avoidance and Pathological Demand Avoidance. One avoids demands because she can, the other because she has to.