It was originated by the Swiss developmental psychologist Jean Piaget (1896–1980 ... By thinking that children have great cognitive abilities, Piaget came up with four different cognitive development ...

Gradually he pieced together a "blueprint" for normal cognitive development in children ... the toy still existed. Piaget found four major developmental stages (with many subdivisions).

"At four or ... preoperational stage at around two years old Despite being over 70 years old, Piaget's theory is "still one of the prevailing theories in terms of cognitive development," Dr ...