Jean Piaget is one of the most influential psychologists of the 20th century. He pioneered research on the development of cognition in children, and his theory has been widely recognized in psychology, education, and many other disciplines related to the human mind.

Why are his search and theory so important?

Reason #1. Piaget's research demonstrates that the development of the human mind is similar to the evolution from egocentrism to social centrism.

Newborns recognize everything they sense as extensions of their selves, including their reflexes, sensations, and movements. Anything out of their direct senses does not exist. As they grow, they gradually establish the theory of mind –– to understand that other people have their own thoughts, beliefs, and desires, which may differ from theirs.

Reason #2: Piaget's research shows how children's reasoning gradually separates from perception.

In newborns' minds, they are their own senses. Around the age of 4, they start to realize that things are not what they appear. This developmental process enables the children to view the external world objectively. 

Here is an example Robert Kegan gave in his book The Evolving Self. A father brought his two boys to the top of the Empire State Building. The younger boy exclaimed: "Look at the people. They're tiny ants." the older boy said, "Look at the people; they look like tiny ants." 

Reason #3:Piaget's theory suggests schema assimilations and accommodations underlie learning and cognitive growth.

Piaget's research supports the idea that concepts and schemas shape human intelligence. When children perceive novel objects or events, they first respond to assimilating them in a way consistent with their existing mental schemas. If they experience differences or conflicts, they would either modify the existing schemas or create new ones to make fit. Piaget refers to the process as accommodation. The constant assimilations and accommodations drive children's cognitive learning and intelligent growth since birth.

Reason #4:Piaget's theory emphasizes the developmental and transformative nature of human intelligence.

The human mind develops and matures through the progressive transformations of mental processes in an orderly fashion marked by the biological maturation and corresponding environmental experience. Piaget's theory provides a theoretical framework to examine the crucial impacts of social and cultural factors on human cognition (and emotion) throughout growth.

In sum, Piaget's pioneer work has provided a successful framework for how the human mind gradually makes sense of the world from birth through adolescence to adulthood. The process is not linear but a spiral-like growth that establishes new concepts and schemas with a new equilibrium at each developmental stage.