Using LISREL to analyze genetic and environmental covariance structure.

Martin and Eaves (1977) developed a method for the analysis of genotypic and environmental covariance structure based on the work of J6reskog (1973). Their method is a general approach to the analysis of covariance structure which allows simultaneous testing of hypotheses about the sources and structure of covariation. The method provides maximumlikelihood estimates of genetical and environmental factor loadings and specific variances. Martin and Eaves applied this method to twin data on cognitive abilities published by Loehlin and Vandenberg (1968). To obtain parameter estimates, standard errors of estimates, and chi-square tests, they implemented their method while using a minimization algorithm (EO4HAF) written by the Numerical Algorithms Group (1974). As their implementation--which is, in fact, a rather intricate affair--is not readily available, it would seem worthwhile to consider the possibility of handling their method by the LISREL computer program of J6reskog and S6rbom (1981). The latter program is easily accessible and is widely known. In this paper we first show how LISREL can be used for the genetic analysis