Genetic and environmental structures of personality: A cluster-analysis approach

A cluster analysis was carried out on within-individual and cross-pair correlations among personality questionnaire items for 654 monozygotic and 648 dizygotic twin pairs in an initial sample, and 649 and 649 pairs in a cross-validation sample. The data were from adult Australian twins who had responded in a mail questionnaire to 110 items from two personality inventories. Clustering based on genetic correlations or on unshared environmental correlations among items led to three very similar cross-validated clusters, labeled Emotional, Confident, and Reserved. Unshared environment provided several additional cross-validated clusters. Clusters based on shared environment, on the other hand, failed to cross-validate or to correspond to the clusters from the other two sources.