Brickman and Campbell originally implied that everyone returns to the same neutral set point after a significantly emotional life event. In the literature review, "Beyond the Hedonic Treadmill, Revising the Adaptation Theory of Well-Being" (2006), Diener, Lucas, and Scollon concluded that people are not hedonically neutral, and that individuals have different set points which are at least partially heritable. They also concluded that individuals may have more than one happiness set point, such as a life satisfaction set point and a subjective well-being set point, and that because of this, one's level of happiness is not just one given set point but can vary within a given range. Diener and colleagues point to longitudinal and cross-sectional research to argue that happiness set point can change, and lastly that individuals vary in the rate and extent of adaptation they exhibit to change in circumstance.