Piaget's theory of cognitive development explains how a child constructs a mental model of the world. His contributions focus on a stage theory of child cognitive development, detailed observational studies of cognition in children. An example that I could think of a child that was born with a certain ability to construct the thought is that my youngest sister thought an object did not exist anymore when she did not see the object. When I took her toys away, she completely lost the interest, and did not look for it. However, when she got older, when I took her toy, she looked behind my back and tried to find it. She knew that the toys were somewhere and did existed even she did not see them. Moreover, she called any furry animal a dog because
