Piaget’s theory of cognitive development stages consisted of four stages. The first was the Sensory Motor Stage, birth-2 years. The pre-operational Stage, 2-7 years old. Children aged around 7-12 go through the Concrete Operational stage, and adolescents go through the Formal Operations Stage, from 11-16 perhaps till adult. In the video above the child is in the pre-operational stage, she’s not able to reason at her max, conservation isn’t acquired from the ages 2-7. Children during the pre-operational state only perceive things accordingly to how things appear, they don’t rationalize when making make decisions..