There are several well known theorists who developed their own views on human development. I am going to provide links to several of the more well known theories. Chances are you will not agree with all any one theorist has to say.
The reason I am posting these is because it is an easy way to see how your child with RAD does fit into a stage of development. Chances are it is not one that matches his or her age. Our children suffered trauma. Trauma interferes with development in every way. If you look at some of these charts and find your child's development stage it will help you figure out where you need to go back too. It helps us better understand our children. Understanding makes empathy with our children easier.
So here we go:
Kolhberg's Stages of Moral Development
Piaget's Developmental Theory
Once you start understanding trauma and how it has changed your child's brain, you will be surprised at how much less you will be angry and frustrated. It really is not their fault they have been through all these horrible things. They were not in control of the situation or the adults. They were just little ones. Makes me want to go give them a hug. Even if it is a tree hug. ; )
Have a healing evening.