John Piaget's four stages

            Though Piaget's observations were quite obvious, he still somehow managed to make it into the book. He declared that there are four stages of childhood: sensorimotor stage, pre-operational stage, concrete operational stage, and formal operational stage.
           
            The sensorimotor stage usually runs from about age 0-2. It is when you learn through sensing and moving, hence the name. Object permanence is common in children in this stage. It is the notion that things cease to exist when they are not visible at that moment-just one more example why babies are not the brightest beings on earth.
         
            The pre-operational stage usually is from age 2-6 in the late toddler/early childhood years like the pre-k/kindergarten kids in our school. They cannot see the world conceptually like we can when we are older. One of their limitations is object conservation, which is when they believe that the amount of liquid changes when the shape of the container changes. Another limitation in the pre-operational stage is egocentricism: kids in this stage cannot see another's point of view at all. If I am facing a kid in this stage, he will think I see what is in front of him even though it is in back of me, and he will not be able to say what I see.

          The concrete operational stage is when the kid develops the theory of mind. It usually goes from age 6-11 when the child can do so much. They lose their egocentricism and can think concretely. Their one limitation is that they are not able to think abstractly.

          Finally, when you reach the age of 12, you are finished developing cognitively. In the formal operational stage, you can finally think abstractly. You develop formal thought and judgment based on moral values.

          As obvious as these stages may seem, Piaget did manage to get his name in the book and in many more places somehow.