General intelligence […] is the best-established, most predictive, most heritable mental trait ever found in psychology. Whether measured with a formal IQ test or assessed through informal conversation, intelligence predicts objective performance and learning ability across all important life-domains that show reliable individual differences.

Geoffrey F. Miller, Mating intelligence: frequently asked questions, in Glenn Geher and Geoffrey Miller (eds.) Mating intelligence: Sex, relationships, and the mind's reproductive system, New York London, 2008, pp. 367–391