Neonatal behavior and early temperament: A longitudinal study of the first six months of life.

Two stable clusters of parent-rated temperamental traits, a "drive" and a "regulatory" cluster, are identified in the first six months of life. The relationship among these clusters and neonatal behavior, measured on the Brazelton Neonatal Behavior Assessment Scale, is considered, and the nature of the clusters compared to the results of other studies with similar methodology. Implications of these results for an interactional theory of early development are discussed.