Piaget found four major developmental stages (with many subdivisions). For the first year and a half or two years of life, infants are only aware of sensorimotor experience, and do not connect it ...

"At four or five months ... evidence showing that some skills develop in children much earlier than Piaget's stages suggests. This is partly down to the limitations of 1950s technology.

By thinking that children have great cognitive abilities, Piaget came up with four different cognitive development stages, which he put out into testing. Within those four stages he managed to group ...