Understanding the Genetics of Intelligence: Can Height Help? Can Corn Oil?

Although the subject is controversial, identifying the specific genes that contribute to general cognitive ability (GCA) has seemed to have good prospects, at least among psychological traits. GCA is reliably and validly measured and strongly heritable, and it shows genetically mediated physiological associations and developmental stability. To date, however, results have been disappointing. Human height shows these measurement characteristics even more strongly than GCA, yet data have indicated that no individual gene has more than trivial effects and this is also true for corn oil. The potential for environmental trigger of genetic expression, long recognized in evolutionary and developmental genetics, as applied to these seemingly disparate traits, can help us to understand the apparent contradiction between the heritability of intelligence and other psychological traits and the difficulty of identifying specific genetic effects.