This topic is interesting to me because I have witnessed this type of development in my own son. Also, I feel that make-believe play is very important to a child's development and their view of the world around them. Make-believe play is discussed under Piaget's theory called the Preoperational Stage. I agree that children play and interact while at the same time representing their environment. This representation moves and grows through different levels, as the child gets older.
Representation is like language to children.
This means that they are associating real objects with play rather than the real purpose of the objects. I feel like, at that age, educators are teaching children language and what things are. We say this is a telephone and this is what you do with it. I think that the child's natural development follows Piaget's theory but is also reinforced by caregivers and teachers. Also children engaged in make-believe play tend to focus on themselves at earlier ages and on external objects.