Piaget theory of cognitive development Explains how a child constructs a mental model of the world. He disagreed with the idea that intelligence was a fixed trait, and regarded cognitive development as a process which occurs due to biological maturation and interaction with the environment. Piaget was the first psychologist to make a systematic study of cognitive development. His contributions included a stage of theory of child cognitive development, detailed observational studies of cognition in children, and a series of simple but ingenious tests to reveal different cognitive abilities. He was interested in fundamental concepts like the idea of number, time, quantity, causality, justice, and so on emerged rather than in how they count, spell or solve problems. Piaget was the first psychologist to make a systematic study of cognitive development. His contributions included a stage of theory of child cognitive development, detailed observational stu...