According to Piaget, cognitive development takes place at different rates at different stages of development. At the elementary level, there is not only an increase in children's capacity to learn but also a qualitative change in their thinking process. Piaget has classified the whole continuum into four stages to elaborate on the process of cognitive development. Sensory Motor Period (0-2 years) Pre-operational period (2-7 years) Concrete operation period (7- 11 years) Formal operational period (11-15 years) ​ Key Points The Formal Operational Period: Formal operational period is the fourth stage of Piaget's classification which starts at about the age of 11 years and continues till about the age of 15 years. At the stage of concrete operation (7-11 years), the child requires mainly four concrete operation stages: Mental representation, which mainly requires less inclusion, and Multiple classifications. Characteristics of formal operational period: A stage of thinking about the thinking process rather than merely thinking about the context of thought. A stage of applying different and flexible ways to think about ideas. A stage of real versus possible. Children do not think only about concrete things but start thinking about imaginary things and possible occurrences. At when elementary level children can use deductive logic, scientific approach and abstract thinking while at the primary level children prefer inductive logic. When children start thinking systematically and methodically. Thus by all these references, we can say that the teacher should have to use diagrams to depict hierarchical relationships, Present problems that require hypothetical thinking, Give opportunities to solve problems, and reason scientifically for the children of the formal operational stage. Important Points Stages Changes in child Sensorimotor stage Senses are teachers Reflex actions. Intimate behavior. Pre-operational stage Language development Irreversibility Egocentrism Animism Concrete operational stage Logic begins Reversibility Classification Conservation Formal operational stage General to specific. Abstract thinking. Divergent/Convergent. Creative thinking.