Recent literature suggests a causal link between malnutrition and impaired cognitive development. A selective literature review indicates that the presence or absence of such a link cannot be established. A reanalysis of an experiment indicated after four years of treatment there was no association between cognitive and nutritional status.…

An unfolding model was selected for the scores on the Scale of Intellectual Development to take into account that, for stage-based instruments, agreement with a statement first increases as the student approaches the stage represented by the statement, then decreases as the student progresses beyond that stage. (Contains 21 references.) (Author)

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…

Disparities between European countries and the U.S. in terms of incidence and prevalence of mild mental retardation have become apparent. A model of intellectual performance that might explain disparities and predict future levels of occurrence of mild mental retardation is presented. Such explanations are relevant for theory and policy decisions.…