A confluence model is developed that explains the effects of birth order and family size on intelligence. (Editor)

Discusses the controversy of the relationship between birth order and intellectual performance through a detailed evaluation of the confluence model which assumes that the rate of intellectual growth is a function of the intellectual environment within the family and associated with the special circumstances of last children. (CM)

Introduces the confluence model as a theory specifying the process by which the intellectual environment modifies intellectual development. Using this model, explores the contradiction between prediction of secular trends in test scores by trends in aggregate birth order and the lack of prediction of individual test scores by birth order using…

The hypothesis that the Scholastic Aptitude Test (SAT) score decline is a result of changing American family sizes and configurations is explored. This possible explanation of declining SAT scores had been offered by Robert B. Zajonc in an article discussing the relation between family configuration and cognitive development. Since a number of…