David M. Williams is an Associate Professor of Behavioral and Social Sciences and Psychiatry and Human Behavior, and the Director of the Center for Health Equity Research at Brown University School of Public Health. He studies the interplay between affective and cognitive factors in determining health-related behavior, and the application of this knowledge to the design of health behavior interventions. He has over 70 publications in these areas of research and has received continuous funding from the National Institutes of Health since 2004. Ryan E. Rhodes is a Professor in the School of Exercise Science, Physical and Health Education, the Director of the Behavioral Medicine Laboratory, and the Associate Director of the Institute on Aging and Lifelong Health at the University of Victoria. His primary area of research is the psychology of physical activity and sedentary behavior. He has held over 90 grants for this research and has contributed over 275 publications as well as 20 book chapters and an undergraduate textbook. Dr. Rhodes is a fellow of the Canadian Academy of Health Science, the Society of Behavioral Medicine, and the Academy of Behavioral Medicine Research. He is also a College Member of the Royal Society of Canada. Mark T. Conner is a Professor of Applied Social Psychology at the University of Leeds. He is one of the most highly cited experts on health behavior in the world. His work focuses on understanding, predicting and changing health behaviors. His work includes a number of important empirical studies and reviews of the determinants of health behaviors and intervention studies to change health behaviors in different groups.