Robbie Case was a highly productive neo-Piagetian researcher at the University of Toronto until his untimely death in 2000. Central to Case’s theory is the notion of central conceptual structures, integrated networks of concepts and cognitive processes that from the basis for much of children’s thinking, reasoning, and learning in particular areas(Case, 1991; Case &Okamoto. 1996; Case, Okamoto, Henderson, & McKeough, 1993) Over time, these structures undergo several major transformations, each of which marks a child’s entry into the next higher stage of development.