The level of well-being that a person tends to report—and toward which one may drift back after a positive or negative experience—is thought to be determined at least partly by innate characteristics. Behavioral genetics research indicates that more genetically similar people (identical twins versus fraternal twins, in the research) tend to be closer in their levels of well-being. However, research suggests that a person’s general tendency to experience a certain amount of well-being can enduringly shift due to external factors, including life-altering experiences such as a bereavement or a long-term disability. Given that set points are not always fixed, a person may also be able to reset it in a positive direction through persistent behaviors such as pursuing altruistic goals.