Why do some people risk their lives regularly by placing themselves in extreme and challenging situations? For some, such as astronauts, the extreme environments are part of the job. For others, they involve the thrill and competition of extreme sports, or the achievement of goals such as being the first to reach the South Pole or climb Everest. Whether for sport or employment, all these people have made the personal choice to put themselves in environments in which there is significant risk. What drives such people? And what skills and personality traits enable the best to succeed? What...