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…

A model-fitting analysis of the covariance structure of an intelligence quotient (IQ) data set is reported using a model that considers additive and nonadditive genetic parameters and shared and nonshared environment parameters that permit different estimates for different types of relatives. The use of LISREL for such purposes is reviewed. (SLD)

This paper repudiates Jensen's hypothesis that differences in IQ scores and scholastic achievement in Negro and white children are genetically based. Specifically, Jensen's identification of IQ scores as a measure of abstract reasoning and problem solving and of levels of ability, and his evaluation of the magnitude of the genetic component in IQ…