An outline of the history of the development of psychology will remain incomplete without mentioning the contributions of Swiss scientist, Jean Piaget. His monumental theory of cognitive development, based on the observations mainly of his own children, has profound influence on contemporary developmental psychology. As a prolific writer, he published his first article in 1907, when he was only 10 years old, and since then, he has published more than 30 books and 200 articles. His theory of cognitive development has provoked hundreds of psychologists to carry out research in intellectual development of children.
He considered that human beings actively interpret information with the help of cognitive structures. Human beings, as behaviorists claimed, are not passive recipients of environmental stimulation. According to Piaget, human beings actively construct and organize knowledge, which helps them to adapt to their environment. His emphasis was on how children understand the world, and represent information in their minds.