A Swiss Psychologist, Jean Piaget established a work which discuss a intellectual development which was concerned with the mechanisms by which intellectual development takes place and the periods through which children develop. Piaget believed that the child explores the world and observes regularities and makes generalizations—much as a scientist does. He eventually came to believe that intelligence is a form of adaptation, wherein knowledge is constructed by each individual through the two complementary processes of assimilation and accommodation, and that intellectual development occurs in four distinct stages. The sensorimotor stage begins at birth, and lasts until the child is approximately two years old, at this stage, the child cannot form mental representations of objects that are outside his immediate view, so his intelligence develops through his motor interactions with his environment. The preoperational stage typically lasts until the child is 6 or 7, this is the stage where true "thought" emerges. Preoperational children are able to make mental representations of unseen objects, but they cannot use deductive reasoning. The concrete operations stage follows, and lasts until the child is 11 or 12. Concrete operational children are able to use deductive reasoning, demonstrate conservation of number, and can differentiate their perspective from that of other people. Formal operations is the final stage and its most important feature is the ability to think abstractly.
