Methodology for Genetic Studies of Twins and Families

Abstract

This book has its origin in a week-long intensive course on methods of twin data analysis taught between 1987 and 1997 at the Katholieke Universiteit of Leuven in Belgium, the University of Helsinki, Finland, and the Institute for Behavioral Genetics, Boulder, in Colorado. Our principal aim here is to help those interested in the genetic analysis of individual differences to realize that there are more chal- lenging questions than simply Is trait X genetic? or What is the heritability of X? and that there are more flexible and informative methods than those that have been popular for more than half a century. We shall achieve this goal primarily by considering those analyses of data on twins that can be conducted with the Mx program. There are two main reasons for this restriction: 1) the basic structure and logic of the twin design is simple and yet can illustrate many of the conceptual and practical issues that need to be addressed in any genetic study of individual differences; 2) the Mx program is well-documented, freely available for personal computers and Unix workstations, and can be used to apply all of the basic ideas we shall discuss. We believe that the material to be presented will open many new horizons to investigators in a wide range of disciplines and provide them with the tools to begin to explore their own data more fruitfully.