Originally published in 1988, in several respects this book is a tribute to the outstanding career of the late Donald B. Lindsley (1907-2003)who, over a span of more than 55 years, had contributed greatly to the development of research in the fields of neurophysiology, psychophysiology, and experimental psychology. The impetus for the book was a conference held at UCLA to honor Professor Lindsley for his numerous and significant contributions to psychology. The chapters of this book have been written by Professor Lindsley’s colleagues and co-workers, and by former students and postdoctoral fellows. The introductory chapter, written by Lindsley himself, tells of 2000 years of "pondering". The chapter is a discussion of the lengthy history of neurophysiology, psychophysiology, and behaviour. Many of the topics mentioned in this chapter are subsequently presented in the book as reports of ongoing research in the field.