Although it is well established that experience seeking behavior (ES) ispositively related to cognitive functioning, the mechanisms underlying thisassociation are not clearly understood. In a large sample of adult twins andsiblings (N = 864, age range 23–75), we studied the causes ofcovariation between ES and general cognitive ability and we studied whether ESmoderates the genetic and environmental causes of variation in general cognitiveability. Results demonstrate a phenotypic correlation of .17 (p <.001)between general cognitive ability and ES, with a common genetic and commonenvironmental background. Moreover, the extent to which genetic andenvironmental factors are shared between general cognitive ability and ES isincreased in individuals with either lower or higher levels of ES. In addition,the extent to which genetic and environmental factors influence individualdifferences in general cognitive ability in adults partly depended on ES.Standardized influences of additive genetic factors on general cognitive abilityranged from 13% to 99%, with lower estimates in higher levels of ES, whilestandardized estimates of environmental factors ranged from almost 1% to 87%,with higher estimates in higher levels of ES. Hence, ES and cognitive abilityare not only associated through common genetic and environmental factors, butalso via moderating effects of genetic and environmental influences on cognitiveability by ES. These findings have implications for future studies on theassociation between ES and general cognitive ability, and for future research onthe genetics of cognitive ability.