Assortment and Cultural Transmission

Abstract

At the First International Course on Twin Methodology, it was recognized that the analysis of twin data alone has its limitations:

Although the main emphasis of this workshop is on the analysis of twin data alone, it is important to recognize that the analysis of genetic and environmental effects cannot end with twins. There are effects that cannot be resolved with data on twins by themselves including the effects of assortment and the shared environment. Furthermore, any model that we start to build with twin data has to predict the results for other kinship data or it is of very restricted value. (Eaves et al., 1989b)

During the course these authors developed a model for analysis of data from twins and their parents that could be easily accommodated in the existing LISREL program (LISREL VI; Jöreskog and Sörbom, 1986). The model was restricted to a special case of both assortative mating and cultural inheritance in which only shared or common environment, what we have called C in this text, were involved. Because the process of assortative mating — „like marrying like“ — was assumed to involve only C, the model was essentially one of social homogamy. In some situations this may well be a plausible model to adopt (Rao et al., 1974; Morton, 1982) and it is the first model we describe in this chapter.