Behavioral and clinical scientists are largely interested in the behavioral manifestation of a given disorder, which can be thought of as a phenotype. The behavioral phenotypes used in many of the association studies, mostly consisting of diagnostic phenotypes such as alcohol abuse or dependence, are influenced by many different genetic as well as environmental factors. Because there are so many different factors that influence whether an individual receives a diagnosis of alcohol abuse or dependence, it has become increasingly important to identify more specific and narrowly defined behavioral phenotypes (i.e., intermediate phenotypes or “endophenotypes”) that are related to the larger disorder. Endophenotypes are thought to facilitate research in the neurobiology of psychiatric disorders by being more homogenous and narrowly defined than the larger diagnostic phenotype (Gottesman & Gould, 2003). Recent research in behavioral genetics has focused on identifying specific genes underlying individual differences in the vulnerability for the development of an alcohol use disorder. In light of such efforts, the identification of more narrow behavioral phenotypes, or endophenotypes, for alcoholism has received increased attention (e.g., Hines et al., 2005), as
