Cluster analysis of childhood temperament data on adoptees

Cluster analysis is used with behavioral data on 162 adoptees to assess temperament and to test the validity of the temperament typologies described by Thomas and Chess. Data are divided into two groups by sex. Results concur with the Thomas-Chess findings in identifying three main temperament groups: difficult, easy, and slow to warm up. Membership in the difficult group predicted later childhood behavior disorder in both sexes. Differing environmental factors associated with difficulty for males and for females are considered, and directions for further investigation are suggested.