Hal Arkowitz, PhD, until his death in 2019, was Emeritus Associate Professor of Psychology at the University of Arizona. His life work was dedicated to understanding how people change and why they don’t. Dr. Arkowitz has published widely in the areas of psychotherapy and motivational interviewing. A scientist-practitioner for his entire career, he was deeply interested in how science can inform practice and how practice can inform science. William R. Miller, PhD, is Emeritus Distinguished Professor of Psychology and Psychiatry at the University of New Mexico. He introduced motivational interviewing in a 1983 article and in the first edition of Motivational Interviewing(1991), coauthored with Stephen Rollnick. Dr. Miller’s research has focused particularly on the treatment and prevention of addictions and more broadly on the psychology of change. He is a recipient of two career achievement awards from the American Psychological Association, the international Jellinek Memorial Award, and an Innovators Award from the Robert Wood Johnson Foundation, among many other honors. His publications include 65 books and over 400 articles and chapters. His website is https://williamrmiller.net. Stephen Rollnick, PhD, is Honorary Distinguished Professor in the School of Medicine at Cardiff University, Wales, United Kingdom. He is 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 (https://motivationalinterviewing.org). He has worked in diverse fields, with special interests in mental health and long-term health conditions such as 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 four editions of the classic work Motivational Interviewing. He has traveled worldwide to train practitioners in many settings and cultures, and he now works as a trainer and consultant in health care and sports. His website is www.stephenrollnick.com.