Our Section in Bethesda is primarily engaged in studies of schizophrenia and personality formation. I will summarize a number of our ongoing studies, and then briefly focus on a methodological issue: the possibility of twin studies moving beyond their heretofore almost constant, very useful tie to genetic studies.

We have previously reported an elaborate multidisciplinary study of a series of MZ twins discordant for schizophrenia, a smaller number of appropriately matched control twin pairs, and their families, aimed at studying nongenetic factors in the pathogenesis of schizophrenia (Pollin et al, 1965, 1966). We have described three interacting groups of variables which consistently differentiated the schizophrenic and nonschizophrenic twins in the discordant pairs (Pollin and Stabenau, 1965). These included an initial set of nongenetic constitutional differences, including birth size, vigor, and physiological competence; consequent different parental perceptions of, and relationships to, each of the twins in a given pair; and subsequent biological and life history differences, based on evolving personality differences, such as in fearfulness, competence, independence, initiative and the like, differentiating the schizophrenic index and the nonschizophrenic cotwins.