Family size exerts an extremely strong and broad influence on development. The influence is strong in the sense that the effects are long-lasting. It is broad in the sense that it has an impact on many aspects of development, including both cognitive ability and extracognitive (e.g., personality) tendencies. The influence of family size is especially remarkable in comparison to other influences on development. Certainly the school, culture, economic background, and similar factors are notable influences, but the influence of family size is the most direct and probably the more robust. In many ways, those other influences are moderated by the family.
Definition Of Family Size
Family size can be defined in various ways. It may be defined such that all individuals within a household are included. This may include parents and children, but it may also include members of the extended family (e.g., aunts, uncles, grandparents) and sometimes people who are not related by genes. This is, of course, true when there are foster parents or stepparents living with children.
At issue is the definition of family, which has undergone enormous change in the past several decades. This has occurred primarily because of the increased divorce rates and the changing demographics of the United States—and the world. In the United States, immigration has increased the population substantially, and many of the immigrants have brought their own views of family and household to the United States. This holds true in many ways, including such factors as who lives in one household and what is an appropriate family size. The traditional American family from the 1950s and 1960s is no longer the traditional American family.
Factors Related To Family Size
Family size is related to socioeconomic status; families in the lower brackets often have larger families. It is, then, an inverse relationship. Associated with socioeconomic status, and therefore also inversely related to family size, are material and educational resources. Simply put, there are usually fewer resources in larger families. Perhaps most important is that family size is associated with family dynamics. Indeed, the impact of family size probably reflects an influence on family dynamics, including communication and discipline. Often, larger families are more authoritarian and less permissive and democratic. This in turn means that children have fewer opportunities to practice making decisions, and they may grow up thinking that their perspective is relatively unimportant.
Family size determines what experiences and resources a child will have and receive, and those in turn influence development. They are strong influences because the experiences determined by family size are repetitious. The effects on cognition and personality are for this reason said to be overdetermined.
Family size is in some ways a nonshared family influence. It is nonshared in the sense that the different siblings do not share the same family size. A first born, for example, is the only child for a period of time, at which point he or she is in a small family, but only until the next sibling is born. That second born child is never an only child but always has at least one sibling. In that fashion, the siblings do not share certain kinds of experiences. The same thing can be said about each birth-order position and family size. Other nonshared influences on development include socioeconomic status (SES) and parental age. Typically, the first-born child is raised (early in life) in the lowest SES. The parents may achieve seniority of some sort at work, and increase their income, so that siblings born after the first born actually are raised in families in higher SES. Even more certain is that first-born children have the youngest—and least experienced— parents. The parents of a second-born or subsequent child are always older and more experienced parents than the parents of first-born children.
Much of the research on family structure focuses on one aspect of family size, namely sibsize. This represents the number of children (siblings) in the household. Very frequently, children reared in families with a small sibsize—few siblings—have more stimulation and need not share resources. Parental resources and attention are not divided much in smaller families, and children may benefit from adult supervision and interactions. Several cognitive indicators are in fact correlated with sibsize, again in an inverse manner, such that fewer siblings may help each child develop more mature cognitive skills.
These effects are moderated by age gap, the interval between siblings. When the gap is large, the siblings are different because of their levels of maturity, and they need not put any effort into being unique and thus earning parental attention. But when the age gap is small, the siblings may be similar in level of maturity, and they often put some effort into finding ways to be unique. Very frequently, the eldest child in a family is fairly conventional and has a traditional slant to his or her motivations. The eldest might very well excel academically, for example. When this is the case, and if the second-born child is not too much younger—a small gap—the second child tends to go in a very different direction. If the eldest child is in fact fairly conventional, the second born will often be quite unconventional and rebellious. Of course, this may change because of temperament as well as factors such as the sex of the children. If two children are both boys or both girls, they again are quite similar, and there is a tendency to try to be different and unique. If one is a boy and one is a girl, however, they are already different and need not put as much effort into being unique.
The family is quite complicated: age gap, sex of the children, socioeconomic factors, and temperaments all play causal roles and interact with family size to determine what occurs in the family and what experiences will occur.
- Blake, J. (1980). Family size and achie Berkeley: University of California Press. Available from http://ark.cdlib.org/ark:/13030/ft6489p0rr/
- Gaynor, L. R., & Runco, M. A. (1992). Family size, birth order, age-interval, and the creativity of children. Journal of Creative Behavior, 26, 108–118.
- Zajonc, B. (1976). Family configurations and intelligence. Science, 192, 227–236.