Three studies investigated second-, fourth-, and sixth-grade students' understanding of class inclusion hierarchies and the relationship of such understanding to the ability to construct external representations for hierarchically structured information. Children understood hierarchical relations and relations expressed in tree diagrams as early…

Thirty-six kindergartners were asked to respond to questions and construct figures designed to test their knowledge of hierarchical relations. Subjects had considerable knowledge of subset and superset classification, and could draw transitive inferences with little difficulty; however, they appeared to have little appreciation of the asymmetry…

Second, fourth, and sixth graders were given passage of text whose material could be represented as four-level class inclusion hierarchy. Students were asked to construct external representation of passage and answer questions that required them to reason about contents of passage. Quality of representation and performance on question tasks were…