Jean Piaget was a Swiss cognitive theorist who has been one of the most influential researchers on child development. He developed his cognitive-developmental theory based on the idea that children actively construct knowledge as they explore and manipulate the world around them. Piaget was interested in the development of "thinking" and how it relates to development throughout childhood. His theory is one of the most famous and widely-accepted theories in child cognitive development to this day.
The Piaget Model of Development
Piaget believed that as children grow and their brains develop, they move through four distinct stages that are characterized by differences in thought process. In his research, he carefully observed children and presented them with problems to be solved related to object permanence, reversibility, and deductive reasoning. Each stage builds upon knowledge learned in the previous stage. His four stages correspond with the age of the children and include: sensorimotor, preoperational, concrete operational, and formal operational.
The sensorimotor stage occurs from birth to age 2. It is characterized by the idea that infants "think" by manipulating the world around them. This is done by using all five senses: seeing, hearing, touching, tasting and smelling. Children figure out ways to illicit responses by "doing", such as pulling a lever on a music box to hear a sound, placing a block in a bucket and pulling it back out, or throwing an object to see what happens. By the end of this stage, children start to form true mental representations, which is known as deferred imitation.
The preoperational stage occurs from age 2 to age 7. It is characterized by the idea that children use symbols to represent their discoveries. Language development and make-believe play begin during this stage. Logical thinking is still not present, so children cannot rationalize, or understand, more complex ideas. Children at this stage are very egocentric, meaning they focus on themselves and how actions will impact them, rather than on others. By the end of this stage, children start to replace imaginative thought with more realistic ideas of the world.
The concrete operational stage occurs from age 7 to age 11. It is characterized by the idea that children's reasoning becomes focused and logical. For example, children realize a ball does not disappear because a bucket is placed over it; rather, they realize the ball is under the bucket. Children also demonstrate a logical understanding of conservation principles, the ability to recognize that key properties of a substance do not change even as their physical appearance may be altered. For example, a child who understands the principles of conservation will recognize that identical quantities of liquid will remain the same despite the size of the container in which they are poured. Children who do not yet grasp conservation and logical thinking will believe that the taller or larger glass must contain more liquid. Children begin to organize objects by classes and subclasses, but they still think in very linear ways, and can only perceive of ideas that can be observed directly. By the end of this stage, children will develop true mental operations and master the concepts of reversibility, transitivity, and assimilation. Reversibility is the idea that something can be changed back to its original state after it has been altered. Transitivity is the concept of relation - for example, if A is related to B and B is related to C, than A must also be related to C. Finally, assimilation is the absorption of new ideas into a person's existing cognitive structure.
The formal operational stage occurs from age 11 to adulthood. It is characterized by the idea that children develop the ability to think in abstract ways. This enables children to engage in the problem-solving method of developing a hypothesis and reasoning plausible solutions. Children can think of abstract concepts and have the ability to combine various ideas to create new ones. By the end of this stage, children have developed logical and systematic thinking, and can create hypothetical ideas to explain various concepts.