Cognitive and psychological studies of patients with major psychoses are planed as part of a major effort to explore the heterogeneity of these conditions. Emphasis is given to the study of the unaffected first degree relatives of patients. Measures include smooth pursuit eye movements, quality and quantity of thought disorder, delayed response performance, anti saccade, pro saccade, and express saccade latencies. Most of these measures are also recorded in members of 5 large pedigrees in Denmark in which DNA samples are collected for chromosomal linkage analysis.