Are bottom-up and top-down traits in dual-systems models of risky behavior genetically distinct?

Numerous dual-systems models of personality have been posited, which propose that behavior is influenced by two complementary systems. A bottom-up system is characterized by emotion-based drive (e.g., urge for rewarding experience), and a top-down system is characterized by the ability to control those urges. Although evidence suggests that these two systems are distinct and may be important in explaining some behaviors, these constructs are also moderately correlated. Notably, there has been little molecular or behavior genetic research on the genetic distinctness of the two systems central to the dual-systems model. The current study used a national twin sample to investigate the degree to which bottom-up and top-down systems, measured here as personality traits of sensation seeking and lack of planning, respectively, covary through genetic and environmental influences. Whereas the overlap between these systems was primarily comprised of unshared environmental influences (e.g., measurement error and unshared systematic variation) in females, a statistically significant proportion of the overlap was accounted for by genetic factors in men. Further, the genetic factors for these systems were moderately to highly correlated in men (rG = 0.62-0.79). These results provide clear support for a dual-systems model in women; however, these systems appear to share some common genetic influences in men.