Piaget's Cognitive Developmental Theory

Jean Piaget was a child psychologist, professor, author, and biologist. Though he had many academic interests, his primary focus was the child psyche. He did a lot of research in the area of child psychology and his conclusion is what is known as Piaget's Stages of Mental Development. He recognizes four main stages in a child's life:

The Sensorymotor Stage (ages: birth to two),
The Preoperational Stage (ages: 2-7),
The Concrete Operational Stage (ages: 7-12), and
The Formal Operational Stage (ages: 12-15).

The Sensorymotor Stage, says Piaget, is when infants and babies are more concerned with learning about the physical world, objects, and their own physical development.

The Preoperational Stage is when a child is learning and developing verbal skills, including reading and writing.

The Concrete Operational Stage is when a child is beginning to understand abstract concepts, such as numbers and relationships. And, finally,

The Formal Operational Stage is when a child "begins to reason logically and systematically