Parental, Birth, and Infancy Factors in Infant Twin Development
MARTIN G. ALLEN M.D.1,
WILLIAM POLLIN M.D., , and
AXEL HOFFER M.D.2
1 Assistant Professor of Psychiatry, Georgetown University Medical School, 3800 Reservoir Rd., N.W., Washington, D.C. 20007
2 Assistant Clinical Director, Massachusetts Mental Health Center, Boston, Mass.
This report, part of a longitudinal study of ten pairs of twins, delineates personality differences that appear in the first year of life, especially in the areas of dependence-independence, emotionality, sociability, curiosity, and activity-passivity. Other variables that differentiate twins include: birth order, birth size, neurological competence, occurrence of a significant traumatic experience, parental "linkage," and physical development. The findings are discussed in relation to studies of normal development and studies of adult twins discordant for schizophrenia. Although twinship is a special circumstance, the authors believe that the observations of this study are probably valid for personality development in general—more obviously with siblings or dizygotic twins, more subtly with the only or firstborn child.
