There has been a continuing increase in the application of hierarchy theory to the problems of instruction and evaluation, since Gagn6 first used the term "hierarchy" in his theory of how human beings acquire complex skills and knowledge. This article, based on a 1970 symposium of the American Educational Research Association, presents an overview and analysis of the use of learning hierarchies in instruction and research, examines some current research on learning hierarchies, and considers the implications of this research for instructional psychology and for theories of cognitive development.Since Gagn6 first used the term "hierarchy" in his theory of how human beings acquired complex skills and knowledge (Gagn6, 1962), there has been a continuing increase in the application of hierarchy theory to problems of instruction and evaluation. Simultaneously, but apparently independently, developmental psychologists have begun to use concepts of hierarchical dependency in studying sequences of cognitive and psychosocial development. This article examines some current research on learning hierarchies and considers the implications of this research for instructional psychology and for theories of cognitive development.This article is based on the proceedings of a symposium held at the 1970 meetings of the American Educational Research Association. The opening section presents an overview and analysis of the key issues in the study and use of learning hierarchies in instruction and in psychological research. This is followed by summaries of four empirical studies, each of which was presented in detail at the symposium, as an example of a particular approach to work in the field. The concluding section contains commentary of three discussants, representing learning, psychometric and developmental psychologists' points of view.
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