Conceptual differences in the analysis of stimulus equivalence

The emergence of structure from undifferentiated beginnings has long been a fundamental problem in science. in biology the issue was one of form versu s function, and in psychology psychologists struggled with how infants make sense of, and consolidate, the flood of sensory input they are faced with. Although the concept of discriminative responding has proven useful in thi s regard, describing the emergence of structure which sometimes follows con ditional discrimination procedures as stimulus equivalence has had importan t implications for subsequent research in the field. Arising from the plethora of research on stimulus equivalence, the theoreti cal treatises of Sidman (1994), S. C. Hayes (1994), and Horne and Lowe (199 6) have distinguished themselves quickly in a crowded field. As all three o f the substantive positions appear to be developing parallel to each other, some history of the field as well as inherent shortcomings of each of the theoretical positions are discussed. Secondary theories and important new m ethodologies suggest where the field is or should be heading a we are to ke ep sight of our original goals.