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Hundreds of research articles have addressed the relationship between birth order and intelligence. Virtually all have used cross-sectional data, which are fundamentally flawed in the assessment of within-family (including birth order) processes. Although within-family models have been based on patterns in cross-sectional data, a number of equally plausible between-family explanations also exist. Within-family (preferably intact-family) data are prerequisite for separating within- and between-family causal processes. This observation reframes an old issue in a way that can be easily addressed by studying graphical patterns. Sibling data from the National Longitudinal Survey of Youth are evaluated, and the results are compared with those from other studies using within-family data. It appears that although low-IQ parents have been making large families, large families do not make low-IQ children in modern U.S. society. The apparent relation between birth order and intelligence has been a methodological illusion.

Studies examining the link between family size and intelligence have consistently found a negative relationship. Children born into larger families tend to score lower on intelligence tests than children raised in smaller families. One recurrent but unexplained finding is that the relation between intelligence and number of siblings is consistently significant for verbal intelligence but inconsistent for nonverbal intelligence. Here, we conceptualize emotional intelligence as one facet of nonverbal intelligence. The research develops a measure of emotional intelligence and uses it to test the hypothesis that emotional intelligence is positively correlated with family size. The results, based upon a sample of graduate students, support the hypothesized relationship. Implications for the study of family size and intelligence, for refining the conceptualizations and measures of nonverbal intelligence, and for leadership theory, are discussed.

The objective of this research is to examine the importance of variable specification in using economic variable to explain the variance in individual's perceived (1) overall psychological, (2) economic, and (3) non-economic well-being. Results indicate that careful specification of economic variables improves the explained variance of perceived subjective well-being. Specification on dependent variable, life satisfaction, based on a domain-specific scale, proves superior to using the response to the global satisfaction question, 'How do you feel about life as a whole?' Economic variables prove significant in explaining both perceived economic and non-economic domains of life satisfaction. Although its overall effect on life satisfaction is negative, increased family size is found to enhance non-economic life, while detracting from economic aspects of life satisfaction.

Do birth-cohort differences in family configuration brought about by post-World War II increases in fertility explain declines in verbal test scores of young people in the 1960s and 1970s? Data from nine representative samples of the U.S. population in the General Social Survey data file confirm systematic declines in verbal scores for cohorts born in the post-World War II era, but reveal a trend beginning much earlier, at least with cohorts born prior to 1920, and one sustained through cohorts born in the 1960s. Despite the significance of these intercohort patterns, within-cohort factors are much more important in producing variation in verbal scores. Social and economic characteristics of the respondent's family of origin and amount of schooling are associated with the largest differences in vocabulary knowledge. Sibship size has a significant influence on the development of verbal skills, but is relatively less important than other family background factors. Birth order, however, is not independently linked to verbal scores. Finally, owing in part to the relatively weak role of family configuration in producing variation in verbal scores, there is no support for the hypothesis that cohort differences in family experiences account for the trends in verbal ability across cohorts in the U.S. population.

Sibling number is often believed to be positively related to sociability. If true, this relationship would not augur well for a future society of extremely small families. Using a latent-variable MIMIC model and two major national surveys of adults, we examine whether number of siblings is related to sociability among men and women. Our research does not suggest a relationship between sibling number (or most other family background variables) and being affiliative as an adult. This negative finding is theoretically favorable, since it implies that the advantages of small families can be enjoyed without concern for at least one potential negative consequence.

Retherford and Sewell claim that the confluence model of intellectual development is fatally flawed because: (1) mathematical simulations of that model generate numerical values that do not coincide with data they were claimed to fit, once those data are converted to mental age values; (2) the simulations of the confluence model also fail to fit aggregate patterns in the Wisconsin Longitudinal Study; and (3) individual-level analyses of the Wisconsin data contradict predictions of the confluence model. These criticisms are shown to be either irrelevant, erroneous, or both. Retherford and Sewell further conclude that birth-order effects may be 'a social phenomenon that does not exist.' We disagree. Far from contradicting the confluence model, the Wisconsin data lend further support to it.

Confluence theory was originally developed to explain the negative effect of birth order on intelligence, as well as some peculiar effects of birth order on the intelligence of last-born children, in a large set of Dutch data. Subsequently the theory was elaborated to explain positive effects and nonlinear relationships between birth order and intellegence in other data sets. We test the mathematical form of the theory using aggregate data, between-family data, and within-family data from the Wisconsin Longitudinal Study and find no support for the theory. Fundamental flaws are identified in the statistical methods used to fit the model to the Dutch data. When the analysis is done correctly, the fit is very poor. An alternative analysis based on a within-family study design that uses sibling pairs indexed by birth order in the Wisconsin Longitudinal Study finds no evidence of birth order effects on intelligence.

Two findings have consistently emerged from research on parent and adult child relationships. First, older parents are seldom abandoned by their children; and second, the relationship between the two generations is generally rated positively by both. The number of children ('sibsize') may have a significant impact on both the mother's relationship with her children, as well as the amount of time she spends with her adult children. It was hypothesized that contact with adult children increases as the number of children increases, and that the amount of support a woman receives is greater if she has more children. A sample of 3,083 respondents whose mothers were living, and a sample of 1,101 older women with at least one child living were used to test these assumptions. The larger the sibsize, the lower the amount of contact between adult child and parent, but the quality of the relationship is rated higher. These results suggest that when a high degree of obligation exists, daughters' feelings are often more negative. On the other hand, sons with many siblings may neglect their mothers, while still having very positive feelings about the relationship. Being an only child negatively affected mother-child relationships for daughters, but not for sons. The smaller families of recent years may well have an impact on intergenerational relations. Women with larger families had more frequent interactions with children, but were more likely to receive assistance from them. (Consumer Summary produced by Reliance Medical Information, Inc.)

The study examined the proposition that relationships among sibling variables, intellectual ability, and academic achievement vary for children from different family-environment groups. Data were collected from 900 11-yr.-old Australian children and their parents. In the analysis, the children were classified into four family contexts that were defined conjointly by family social status and parents' academic socialization. Within each family group, regression surfaces were constructed from models that included terms to account for possible linear, interaction, and curvilinear associations among the variables. The results suggested the general proposition that within the family-environment groups, sibling variables were not related to academic achievement at different levels of the children's ability. However, the findings indicated that there were variations to this general proposition. Indeed, there were a number of complex associations between the sibling variables and children's academic achievement in the different family-environment groups.

For a sample of 90 persons, all from Essen, with the help of a questionnaire whether the difference in the number of siblings of spouses correlates with self-rated marital satisfaction was examined. This was confirmed for the husbands. Differences in sibling numbers for couples also correlate positively with the significance of sexuality in a relationship and negatively with the declaration of risks of childbirth.

The impact of family on men's IQ scores is estimated using evidence from Norway. Findings indicate that the impact of family size is dependent on the family-size intervention type. The differences in impacts of expected and unexpected family size growth are also examined.

The study examined whether two types of social variables set the stage for the development of sense of community in 236 adults (91 men, 145 women) from 41 of the 67 counties in Alabama. Multiple regression showed both types of social variables, the need for affiliation and having been raised with siblings, were significantly and positively related to scores on a measure of sense of community.

12 adults without siblings expressed common concerns about rearing two or more children but lacked consensus regarding a preference for family size.