The adult who is an only child: achieving separation or individuation

60 women and 60 men between the ages of 18 and 45 years (M = 30.5, SD = 9.6) were categorized by sex, age, and birth order (only child, firstborn, lastborn) to assess the differences among the adult only-child, the youngest child, and the oldest child in autonomous characteristics and cohesiveness in family interaction. Analysis of the responses on a biographical data sheet, the California Psychological Inventory, and the Family Adaptability Cohesion Scales III showed that main effects for birth order and sex are significant in the process of separation-individuation and that the only child is less autonomous than the oldest child.