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Family Size

Family size is a variable of great interest to those who study children. Empirical studies consistently have found a negative association between family size and children's mental ability, intelligence, and educational attainment. Two theoretical explanations have been posited to explain these negative relationships. Dilution theory suggests that as the number of siblings increases, fewer resources (e.g., parental love and attention, finances) are available to facilitate the development of each child. The confluence model offers a more complex explanation that considers the interrelationships among the number of siblings, child spacing, birth order, and parent-child interactions. Although larger families include positive characteristics such as increased family socialization and father involvement, increased family size also is associated with more authoritarian parenting, which, in turn, can negatively impact a child's self-esteem, self- differentiation, and ego identity. Empirical studies have supported certain aspects of these perspectives. Much of this research, however, has been criticized for drawing conclusions based on "between family comparisons" that do not take family-specific variables (e.g., family resources, parents' intelligence, sibling interactions) into account.


Blake, Judith. Family Size and Achievement. Berkeley: University ofCalifornia Press, 1989.

Hoffman, L. W. "The Influence of the Family Environment on Personality: Accounting for Sibling Differences."Psychological Bulletin 110 (1991):187-203.

Kuo, H., and R. M. Hauser. "How Does Size of Sibship Matter?Family Configuration and Family Effects on Educational Attainment." Social Science Research 26 (1997):69-94.

Rodgers, J. L., H. H. Cleveland, E. van den Oord, and D. C. Rowe."Resolving the Debate over Birth Order, Family Size, and Intelligence." American Psychologist 55 (2000):599-612.

Debbie Madden-Derdich

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Social Issues ReferenceChild Development Reference - Vol 3