What is the developmental mechanism that Piaget proposed to account for movement to higher stages of cognitive development? In other words, why do children begin to construct a different type of cognitive structure at different stages? Solution The following are the assumptions of piaget’s about the children. The first important assumption is that the children usually construct their own knowledge .This knowledge is usually In response to their experiences in life.Another important fact is that the children have the power to learn various things on their own without the intervention of older children or adults..It has the following stages Piaget’s Stages: 1)The first one is Sensorimotor stage (birth to 2 years) in which the child grows. 2)The second one the Preoperational stage(2 to 7 years).In this stage the knowledge which is gained by the child is represented by language, mental imagery,and symbolic thought. 3)The third one is the Concrete operational stage(7 to 12 years).In this stage the Children are able to reason logically about concrete objects and events. 4)Finally we have the Formal operational stage(12 years and up)-In this stage the Children have the ability to think deeply about concrete events .They can also reason abstractly and hypothetically at the same time..