G enetic and environmental sources of covariation among cognitive measures of verbal IQ, performance IQ (PIQ), academic achievement, 2-choice reaction time (CRT), inspection time (IT) and the 6 Openness facets of the NEO Personality InventoryRevised (NEO PI-R) were examined. The number of twin and twin-sibling pairs ranged from 432 (182 MZ, 350 DZ/sibling) to 1023 (273 MZ, 750 DZ/sibling) for cognitive measures, and between 432 (90 MZ, 342 DZ/sibling) -437 (91 MZ, 346 DZ/sibling) for Openness facets. Structural equation modeling best supported a model with a 3-factor additive genetic structure. A genetic general factor subsumed the 5 cognitive measures and 5 of the 6 Openness facets (Actions did not load significantly). A second additive genetic factor incorporated the 6 Openness facets, and a third additive genetic factor incorporated the 5 cognitive measures. Specific additive and dominance genetic effects were also evident, as were shared common and shared unique environmental influences, and specific unique environmental effects. The Openness facets of Ideas and Values evidenced the strongest phenotypic correlations with cognitive indices, particularly verbal measures. The genetic correlations among Openness facets and cognitive measures ranged from -.06 to .79. Results were interpreted as suggesting that Openness is related to general cognitive ability (g) through a genetic mechanism and that g engenders a minor but discernable disposition towards Openness for the majority of facets.There has been growing interest in clarifying the relationship between openness to experience (Openness) and cognitive measures such as IQ and basic mental speed tasks (e.g., Bates & Shieles, 2003; ChamorroPremuzic et al., 2005;Gignac et al., 2004). Recent evidence has indicated that measured aspects of Openness (facets) may be related to general cognitive ability (g; Chamorro-Premuzic, et al., 2005;Gignac, 2005;Gignac et al., 2004), suggesting that shared genetic influences may be implicated. In this article, we examine genetic and environmental structures underpinning relationships among the six facets of the Openness domain of the Revised NEO Personality Inventory (NEO PI-R) and cognitive variables including Verbal IQ (VIQ) and Performance IQ (PIQ), academic achievement (Queensland Core Skills Test [QCST]), and two measures of processing speed, choice reaction time (CRT), and inspection time (IT).Openness is one of five core domains of personality defined by the NEO PI-R. It is composed of six facets characterized by: 1. appreciation of art, poetry, music, and beauty (Aesthetics) 2. engagement of one's imagination (Fantasy) 3. valuing of emotion, and the experiencing of more intense emotions (Feelings) 4. involvement in varied experiences, and enjoyment of novelty (Actions) 5. pursuit of a manifold array of cultural and intellectual interests (Ideas) 6. questioning of conventional norms and receptivity to unconventional principles (Values; Costa & McCrae, 1992).In contrast to an abundance of studies of heritability of g, whic...