In the early 1980s, the Wisconsin Center for Education Research sponsored a conference that brought together researchers from the United States and abroad who were beginning to focus their attention on children's addition and subtraction concepts and skills. The publication of Addition and Subtraction: A Cognitive Perspective1 was an outcome of this conference. Following the conference, a number of researchers adopted common perspectives on critical problems in the study of the development of addition and subtraction concepts. Since the early 1980s, a great deal of progress has been made in understanding how addition and subtraction concepts develop in children. Furthermore, recent studies have begun to demonstrate that this knowledge has major implications for classroom instruction and student learning.
Current research on the teaching and learning of rational number concepts is about where addition and subtraction research was at the time of the conference. There is an emerging consensus regarding some of the most critical problems in studying the teaching and learning of rational number concepts and skills, and researchers are beginning to share a common perspective for studying them. But there are some important differences between the earlier work on addition and subtraction and the work that is represented in this volume. In the early 1980s, the emphasis was on student thinking; there was almost no discussion of classroom instruction. This volume is concerned with the integration of research on teaching,____________________