As any family doctor can tell you, the greatest potential for improving health care isn’t discovering new treatments for disease, it’s getting patients to do the things we already know work—exercising, quitting smoking, eating right, and taking medications regularly. Despite astounding success in highly technical areas such as immunotherapy, genome editing, and surgical robotics, medicine has been unable to solve the most basic challenge of helping patients make good decisions for themselves. This challenge lies at the heart of the nation’s most pervasive health problems: diabetes, obesity, cardiovascular disease, depression, chronic pain, and many cancers.