The challenge of understanding the origins, precursors, and core abnormalities of schizophrenic disorders has led a number of investigators to the socalled high-risk method during the last three decades. To avoid confounding the consequences of these disorders with their causes and precursors, investigators have focused on individuals who are not manifesting schizophrenic disorders, but who are at increased risk for their development (Garmezy, 1974, 1978; Garmezy & Streitman, 1974). The most popular of these strategies has been the study of children born to a schizophrenic parent, whose risk for schizophrenia is known to be substantially higher than the population base rate. Estimates of the eventual incidence of schizophrenia among children of a schizophrenic parent range from 3% to 15%, depending on the breadth of the diagnostic criteria employed and other factors, an incidence 10 to 15 times the base rate for comparable populations (Gottesman & Shields, 1982; Kendler, Gruenberg, & Tsuang, 1985). In addition, considering the data from twin and adoption studies, one can assume that some offspring of a schizophrenic parent who do not develop schizophrenia nevertheless have an increased genetic vulnerability to such disorders.

The Minnesota High-Risk Studies, which were developed under the overall direction of Norman Garmezy and are part of a larger research program entitled Project Competence, have employed this research strategy in a series of investigations focusing on potential vulnerability factors and prodromal anomalies in schizophrenic disorders. This chapter integrates data from several studies in the final phase of the Minnesota High-Risk Studies. First, we shall present the overall subject recruitment strategy and the individual studies of attention and cognition that were completed during this phase.