Genetic Influence on Family Systems: Implications for Development.

In this article, my major objective is to describe recently observed connections between genetic processes and family systems. In describing these connections I hope to show how new findings in genetics may give us a clearer idea of the role that families play in the differences among us: differences in healthy and adaptive development and differences in pathological and maladaptive development. I will provide some new data, some of it yet unpublished, from behavioral genetic research. I go somewhat beyond the data currently available, and lay out some very preliminary speculations about genes, families, and development. In doing so, I wish to take advantage of two important trends in the study of human development. The first of these is an increasing emphasis on individual differences in development rather than on stages or transitions in development that are common across individuals. The second trend is increasing attention to biological factors that shape changes in individuals across time and that account for differences in the rates and patterns of change. I will argue here, as have several before me, that a detailed study of family process in relationship to biological factors provides an excellent opportunity to test and revise developmental theories that combine biological and psychosocial data. John Gottman (1994) has pioneered the integration of family process and psychophysiological data. Janice Kielcolt-Glaser has taken the initiative in relating family process and immunological data (Dura & Kielcot-Glaser, 1991). A chapter by Troost and Filsinger (1993) in Sourcebook of Family Theories and Methods outlines a number of theories relating evolutionary processes to family process. This essay centers on genetics as a central link between psychosocial and biological modes of thought about development. Certain properties of genes permit powerful research designs and strong inferences about development. First, we know how individuals acquire their genes. This permits us to say, with security, that every child shares exactly 50% of his or her genes with each biological parent, approximately 50% with each sibling, exactly 100% with its identical twin, and approximately 25% with each half sibling. We also know that genes are finite in number. We can search for single genes that have major effects on behavior, the so-called single gene effects. We can also search for sets of genes that collectively produce certain types of behavioral variation, the polygenic effects. Of particular importance, we can ask of any two behaviors--say parenting behavior in a mother and antisocial behavior in her child--whether they are influenced by the same genes or by different genes. Moreover, the pathways by which genes express themselves in behavior are beginning to be mapped out. In this essay I will emphasize one new idea in this domain: Genes influence behavior by influencing an individual's exposure to certain types of environmental experience. For example, we have preliminary evidence that genes influence the level of irritability and anger that adolescents receive from their parents (O'Connor, Hetherington, Reiss, Plomin, in press; Plomin, Reiss, Hetherington, & Howe, 1994). That is, heritable characteristics of adolescents have systematic effects on the negative parenting that they receive from their mothers and fathers. This genetic influence may play an important role in how genes influence differences among adolescents in levels of self-control, self-esteem, and social responsibility. Taken together, these concepts of genetic endowment, discrete genetic effects, and mechanisms of genetic expression open up a new world of questions and powerful research designs for family scholars. It is also important to set aside, at the outset, certain misconceptions about genes. First, genes do not determine behavior; they are not biological juggernauts. The word influence is much more appropriate, considering the many biological and social events that intervene between the structure of genetic DNA and complex human behaviors. …