Stephen Rollnick, PhD, is Honorary Distinguished Professor in the School of Medicine at Cardiff University, Wales, United Kingdom. He is a cofounder of motivational interviewing, with a career in clinical psychology and academia that focused on how to improve conversations about change, and helped to create the Motivational Interviewing Network of Trainers.

He has worked in diverse fields, with special interests in mental health and long-term health conditions like diabetes, heart disease, and HIV/AIDS. Dr. Rollnick has published widely in scientific journals and has written many books on helping people to change behavior. He is coauthor (with William R. Miller) of the classic work Motivational Interviewing: Helping People Change, now in its third edition. He has traveled worldwide to train practitioners in many settings and cultures, and now works as a trainer and consultant in healthcare and sports. 

William R. Miller, PhD, is Emeritus Distinguished Professor of Psychology and Psychiatry at the University of New Mexico. Fundamentally interested in the psychology of change, he is a cofounder of motivational interviewing and has focused particularly on developing and testing more effective treatments for people with alcohol and drug problems. Dr. Miller has published over 400 scientific articles and chapters and 50 books, including the groundbreaking work for professionals Motivational Interviewing, Third Edition. He is a recipient of the international Jellinek Memorial Award, two career achievement awards from the American Psychological Association, and an Innovators in Combating Substance Abuse Award from the Robert Wood Johnson Foundation, among many other honors. The Institute for Scientific Information has listed him as one of the world's most highly cited researchers.