I argue that the g factor meets the fundamental criteria of a scientific construct more fully than any other conception of intelligence. I briefly discuss the evidence regarding the relationship of brain size to intelligence. A review of a large body of evidence demonstrates that there is a g factor in a wide range of species and that, in the species studied, it relates to brain size and is her...

The purpose of this article is to present the value of using quantitative genetic approaches to understanding individual differences and ethnic diversity in aging. There are three major points to be discussed: 1) the difference between race and ethnicity, 2) inter-versus intra-group differences, and 3) the contribution of quantitative genetics methods to understanding individual variation withi...

Epistasis, i.e., the fact that gene effects depend on the genetic background, is a direct consequence of the complexity of genetic architectures. Despite this, most of the models used in evolutionary and quantitative genetics pay scant attention to genetic interactions. For instance, the traditional decomposition of genetic effects models epistasis as noise around the evolutionarily-relevant ad...

Genetic analysis of quantitative traits is applied in a wide variety of substantive research areas. Many human characteristics exhibit continuous variation, such as height, weight, intelligence or personality, but the application of quantitative genetics is not limited to traits thought to be continuous. For example, eye color may be assessed in a qualitative fashion – blue versus brown versus ...

Essentially all characters show some phenotypic variation, either between individuals within a population and/or between populations. Such variation is probably due to both genetic and environmental differences. Sorting out the nature of these genetic differences, the relative importance of genetic versus environmental factors, and how this phenotypic variation translates into evolutionary chan...

Introduction In the chapter on Mendel and Morgan, we saw how the transmission of genes from one generation to another follows precise mathematical formula. The traits discussed in that chapter, however, were discrete traits—peas are either yellow or green, someone either has a disorder or does not have the disorder. But many behavioral traits are not like these clear-cut, have-it-or-don’t-have-...