BEHAVIORAL GENETICS is a theory and a set of methodologies that assesses the etiology of individual differences in a population. Behavioral genetic methodologies can answer questions about why some children develop diabetes or why some individuals are more prone to heart attacks or high blood pressure, but the approach is less relevant to questions regarding group differences, such as why women on average live longer than men. In other words, this theory is applicable to individual differences in behavioral characteristics but can provide little information about the average differences between groups (e.g., differences between males and females or between members of different cultures). Although the focus of research in this area is often on genetic influences on health and behavior, the theory is also useful for describing environmental sources of variance that contribute to individual differences. Thus, the label of behavioral genetics is misleading, because the theory and methods are as informative about environmental influences on characteristics as they are about genetic factors.