The aim of the study was to investigate the relationship between the Flynn effect and the effects of age differences between siblings on the intelligence difference between them. In Norway, the secular trends in intelligence-test score means vary both in magnitude and direction. We identified three periods: one period where the mean intelligence…

Responds to "Birth Order and Intelligence: Further Tests of the Confluence Model" by Robert D. Retherford and William H. Sewell. Reviews their arguments and suggests that their analyses of the Wisconsin Longitudinal Study data support rather than contradict the model. (CJS)

Examines the contiguity of siblings within family structure--a concept reflecting how much of the family environment siblings share with one another--in relation to within family IQ scores. Results fail to demonstrate family structure effects. (HOD)

Intelligence tests were administered to a stratified sample of 4058 school children from Palermo, Sicily. I.Q. scores were found to be positively correlated with socioeconomic status and negatively related to family size. As birth order increased, mental development decreased. Implications for future research were discussed. (EH)

The differential impact of birth order and IQ on sibling roles were examined with particular interest focused on achievement outcomes. Subjects were a stratified sample of 37 pairs of near-in-age siblings, all within the normal range in personality and IQ, but differing significantly in scores on the Slosson IQ Test. Results indicate that when the…

Very close age spacing was an obstacle to high academic performance for later borns. In family relations and self-esteem, first borns scored better and performed in school as well as their potentially much more able younger siblings, regardless of age spacing. (Author)

When differences in level of motivation were controlled, all of the previously found differences between firstborn and later born disappeared. (Authors)

Individual differences in general intelligence and in 8 different special aptitudes or skills were hypothesized to be independent of family size and birth order indices. Evidence to the contrary, in the form of linear correlations, was predicted to be due to the confounding influence of socio-economic factors. Among the more familiar demographic…

Research on sibling influence on intellectual ability has shown that academic ability and achievement decrease as family size increases and as spacing between siblings decreases. Research also suggests a relationship between sex of subject and of sibling, and age differences in the effects of birth order and sibling sex. (JAC)

Support for the confluence model of intellectual development has come from analyses of family size-birth order means of large aggregate data sets. Analyses of individual scores do not substantiate the confluence model, as explained variance is markedly reduced. The study of family interaction variables utilizing longitudinal data is recommended.…

This issue of a research journal on gifted education examines a number of research projects that delve into questions of how family life affects intelligence, especially among gifted children. Specific articles include: (1) "Are We Raising Smarter Children Today?" (Wendy M. Williams), which discusses the effects of school-related factors…

According to confluence theory, a child is helped or hindered in intellectual development according to the average absolute intelligence (mental age) in the family when the child is born. An analysis of test scores, family information, and socioeconomic data of 36,000 college applicants in Colombia failed to support this theory. (Author/CP)

The confluence model of cognitive development was tested on 7,060 children. Family size, sibling order within family sizes, and hypothesized age-dependent effects were tested. Findings indicated an inverse relationship between family size and the cognitive measures; age-dependent effects and other confluence variables were found to be…

Confluence theory was developed to explain the negative effects of birth order on intelligence. Using aggregate, between-family, within-family, and paired-sibling data from the Wisconsin Longitudinal Study, tests the mathematical form of confluence theory and finds no support for it. Suggests that statistical methods used to fit the model to the…