This book was conceived many years ago as an abstract goal for a father-son team when the father was working in university administration and the son was just getting into the academic business. Eventually, the father returned to the laboratory, the son began to get his feet on the ground, and the goal became concrete. Now the work is finished, and our book enters the literature as, we hope, a valuable contribution to understanding the terribly complex and subtle problem of the neuro- biology of motivated behaviors. We would also like the book to stand as a personal mark of a cooperative...