The authors describe a program of research in the application of scalogram analysis to the validation of learning hierarchies, together with the development of an alternative method for assessing hierarchical relationships among tests of instructional objectives. The relationship between scalability of tests and positive transfer between objectives in the course of learning is discussed and experimental transfer studies testing hierarchical hypotheses are described. Related research by developmental and learning psychologists and by test designers is discussed along with the authors' own research. (Author)