"The scientific study of cognitive development in young children traces its roots back to Jean Piaget, a pioneer of this field in the twentieth century (Piaget, 1954, 1983). From infancy to adolescence, children progress through four psychological stages: (1) the sensorimotor stage from birth to two years (when cognitive functioning is based primarily on biological reactions, motor skills and perceptions); (2) the preoperational stage from two to seven years (when symbolic thought and language become prevalent, but reasoning is illogical by adult standards); (3) the concrete operations stage from seven to twelve years (when logical reasoning abilities emerge but are limited to concrete objects and events); and (4) the formal operations stage at approximately twelve years (when thinking about abstract, hypothetical, and contrary-to-fact ideas becomes possible). According to Piaget, the child, like the logician or mathematician, "models" objects, their properties, and their relations through a succession of cognitive frameworks, from primary biological reactions and motor skills to high-order formal thinking. After the age of twelve, children model a formal hypothetico-deductive logic that ultimately resembles the rational logic of scientists and mathematicians. Piaget was the first psychologist to take children's thinking seriously. His genius was based on the idea of building his child development theory on triple roots in epistemological, biological, and logico-mathematical foundations. Consequently, Piaget is now recognized as one of the precursors of cognitive science during the last century (Fischer & Kaplan, 2003)"--