General Intelligence (g): Overview of a Complex Construct and Its Implications for Genetics Research

Current technology has dramatically increased the prevalence of studies to establish the genetic correlates of a wide variety of human characteristics, including not only the physical attributes that determine what we look like and the risk of physiological disease but also the psychological and cognitive characteristics that often define who we are as individuals. Perhaps one of the most deeply personal and often controversial characteristics is the concept of general intelligence, known in the psychological literature as "g." As with the genetic study of any complex trait, the first step in studying the genetics of g is to carefully define the characteristic of interest. For g, this entails establishing what intelligence means and providing a clear operational definition for how it will be measured. In this paper, we provide a brief historical and theoretical overview of the construct of general intelligence, describe its relationship to the contemporary measurement of intelligence, and discuss these concepts in light of the challenges associated with defining g as a characteristic in the study of genetics.