The following are some of the important characteristics of the five factors. First, the factors are dimensions, not types, so people vary continuously on them, with most people falling in between the extremes. Second, the factors are stable over a 45-year period beginning in young adulthood (Soldz & Vaillant, 1999). Third, the factors and their specific facets are heritable (i.e., genetic), at least in part (Jang, McCrae, Angleitner, Riemann, & Livesley, 1998; Loehlin, McCrae, Costa, & John, 1998). Fourth, the factors probably had adaptive value in a prehistoric environment (Buss, 1996). Fifth, the factors are considered universal, having been recovered in languages as diverse as German and Chinese (McCrae & Costa, 1997). Sixth, knowing one's placement on the factors is useful for insight and improvement through therapy (Costa & McCrae, 1992).