Cognitive development involves cognitive processes such as knowing, thinking, remembering, recognizing, categorizing, imagining, reasoning, decision-making, and so forth.According to Piaget, childrens understanding of the world expands as they experience new ideas and challenges. Children construct their own knowledge through interaction with their surroundings.Cognitive development proceeds as children mature. Piaget divided cognitive development into four stages.Sensorimotor (Birth “ 2 years) & Preoperational (2-7 years)Concrete Operational (7-11 years) & Formal Operational (11 years and above)?The Pre-operational Stage:In this stage, the child faces problems with the irreversibility of thought, the concept of conservation, and struggles with the idea of centration.Conservation refers to the idea that a quantity remains the same despite changes in appearance. If you show a child four marbles in a row, then spread them out, the preoperational child will focus on the spread, and tend to believe that there are now more marbles than before.The Concrete Operational Stage:In this stage, children can solve conservation problems because of the attainment of the concept of reversibility, decentralization, seriation, and transitivity as a cognitive capacity.Reversibility is the ability by which the child becomes capable of following a series of actions and then being able to follow back or in other words reverse these series of actions mentally.Decentralization refers to the ability to consider multiple aspects of a situation. When a child can focus on more than one aspect of a situation at the same time they have the ability to decenter.Hence, it is clear that according to Jean Piaget, a childs ability to solve conservation problems depends upon an understanding of decentralization and reversibility aspects of reasoning.Additional Information Seriation: It is the ability to order items along a particular dimension such as length or weight. For instance, arranging pencils from shortest to longest.Transitive inference: It is the process of finding unknown relationships between objects by using multiple previous information. If stick A is longer than stick B and stick B is longer than stick C, children can draw the mental inference that stick A is longer than stick C.Centration: Due to the Centration in thought, the child can focus his attention only on one aspect of the situation at a time and cannot reverse the direction of his thought.