Research by Kurt Gray, a doctoral student in psychology at Harvard, shows that a person's capacity for willpower and physical endurance increases if they perceive themselves as good or evil. "Evil" acts in particular give a person a large boost in physical strength. From the article: “'People perceive those who do good and evil to have more efficacy, more willpower, and less sensitivity to discomfort,' Gray said. 'By perceiving themselves as good or evil, people embody these perceptions, actually becoming more capable of physical endurance.' Gray’s findings run counter to the notion that only those blessed with heightened willpower or self-control are capable of heroism, suggesting instead that simply attempting heroic deeds can confer personal power."