Steven C. Hayes, Ph.D. is Nevada Foundation Professor at the Department of Psychology at the University of Nevada. An author of more than twenty books and more than 325 scientific articles, his career has focused on an analysis of the nature of human language and cognition and the application of this to the understanding and alleviation of human suffering. In 1992 he was listed by the Institute for Scientific Information as the 30th "highest impact" psychologist in the world during 1986-1990 based on the citation impact of his writings. Dr. Hayes has been President of Division 25 of the American Psychological Association, of the American Association of Applied and Preventive Psychology and of the Association for Advancement of Behavior Therapy. He was the first Secretary-Treasurer of the American Psychological Society, which he helped form. He has received the Don F. Hake Award for Exemplary Contributions to Basic Behavioral Research and Its Applications from Division 25 of the American Psychological Association and was appointed by HHS Secretary Donna Shalala to a 5 year term on the National Advisory Council on Drug Abuse in the NIH.