Abstract
Although research findings have revealed that both genetic and environmental factors contribute to variation in IQ at the individual level, no studies have examined how genetic differences contribute to differences in IQ within and between families. The current study uses data drawn from the National Longitudinal Study of Adolescent Health (Add Health) to examine the potential role genetic factors play in shaping differences in IQ scores within and between families. The results revealed that while genetic variation between family members did not significantly predict differences in IQ scores, family-level dopaminergic risk scores did significantly predict differences in family-level IQ. The implications of the results are elaborated upon, and suggestions for future research are discussed.