The use of quantitative genetic methodology to gain insights into the origins of individual differences in later life.

There is great interest in the interindividual variability in aged populations. Knowledge of the etiology of these individual differences may lead to a more comprehensive understanding of aging. The purpose of this article is to discuss the use of quantitative genetic (or behavioral genetic) methodology to identify sources of individual variation in later life. These methods can provide insights into the proportion of environmental and genetic influences on behavior. Some of the basic procedures used in quantitative genetic analyses and their rationales are provided. In addition, the use of structural equation modeling to model genetic and environmental effects is discussed. Lastly, some of the special issues involved in quantitative genetic research on aged populations are discussed.