Children's understanding of class inclusion hierarchies: the relationship between external representation and task performance.

Three experiments were designed to investigate children's understanding of class inclusion hierarchies and to determine whether such understanding may be related to children's ability to construct external representations for information that was hierarchical in nature. Understanding of hierarchies was studied through tasks designed to demonstrate children's ability with subset/superset classification and knowledge of asymmetric and transitive relations. Children were asked to construct their own external representations for passages containing information that could be represented hierarchically. It was hypothesized that the quality of children's external representations would be related to their ability to respond to questions related to the passages. Children's responses to questions, as well as their external representations, suggested that children as young as second grade have substantial understanding of hierarchical relations. Although the external representations were constructed in drawing, written, or structured modes, the data revealed a strong relationship between the quality of children's external representations and their performance on question tasks requiring both recognition and reasoning. Finally, children understood the relationships expressed in tree diagrams and could construct such diagrams to respond to questions. Implications of the findings, particularly as related to note-taking skills, and suggestions for further research are discussed.