The papers in this volume were prepared after a preliminary symposium held at The University of Michigan in honor of Clyde Coombs. Following the symposium, each paper was extensively revised and in many instances completely rewritten to provide a timely and provocative survey of current works in mathematical psychology in the style of Clyde Coombs. All of the authors were students or colleagues who were closely influenced by Coombs and our intention was not to cover all approaches to the field, but rather to illustrate the continuing influence of Coombs's work and approach to the application of mathematics to basic psychological phenomena. If we are successful, it is because of his influence on the contributors. v Acknowledgements The preparation of this volume in memory of Clyde Coombs owes much to the many friends, students, and colleagues of Clyde Coombs who generously provided their support and encouragement. Funding was provided by Dean John D'Arms of the Horace H.