Does cultural background influence the intellectual performance of children from immigrant groups?

This paper addresses both the construct validity and the criterion-related validity of the "Revisie Amsterdamse Kinder Intelligentie Test" (RAKIT), which is a cognitive ability test developed for primary school children. The present study compared immigrant primary school children (N = 559) and Dutch children (N = 604). The mean scores of Surinamese/Netherlands Antillean, Moroccan, and Turkish children differed from each other and were lower than those of the Dutch children. Comparison of the test dimensions showed that group differences with respect to the construct validity were small. We found some item bias, but the combined effects on the sum score were not large. The estimate of general intelligence (g) as computed with the RAKIT showed strong predictive validity for most school subjects and standardized achievement tests. Although some criteria revealed significant prediction bias, the effects were very small. Most of the analyses we performed on differences in test scores and differences in criterion scores supported Spearman's hypothesis that g is the predominant factor determining the size of the differences between two groups. The conclusion that the RAKIT can be used for the assessment of groups from various backgrounds seems warranted

Improved iodine status is associated with improved mental performance of schoolchildren in Benin.

Background: An adequate iodine supply in utero and shortly after birth is known to be crucial to an individual's physical and mental development. The question of whether iodine supplementation later in life can exert a favorable influence on the mental performance of iodine-deficient populations was addressed in various studies, but with contradictory results. Objective: The aim of this study was to examine the effect of an improvement in iodine status on mental and psychomotor performance of schoolchildren (7-11 y) who were moderately to severely iodine deficient. Design: The study, which was originally planned as a double-blind, randomized, placebo-controlled intervention, was carried out in an iodine-deficient population of schoolchildren (n = 196) in northern Benin. As the population began to have access to iodized salt during the 1-y intervention period, the study population was split post hoc - on the basis of urinary iodine concentrations - into a group with improved iodine status and a group with unchanged iodine status. Changes in mental and psychomotor performance over the intervention period were compared. Results: Children with increased urinary iodine concentrations had a significantly greater increase in performance on the combination of mental tests than did the group with no change in urinary iodine concentrations. Conclusions: An improvement in iodine status, rather than iodine status itself, determined mental performance in this population, which was initially iodine deficient. These findings suggest a 'catch-up' effect in terms of mental performance

Twin-Singleton Differences in Intelligence?

Introduction Classic behavioural genetic studies provide statistical estimates of heritabilities that form the first step in the search for genes for complex behaviour. 1,2 A large part of these behavioural genetic studies are based on twin samples. These samples have sometimes been criticised for their alleged non-generalisability; since twins are `special' they may not be representative of singletons. Especially in the field of cognitive abilities twins are generally considered to be at a disadvantage compared with singletons. 3--6 Twins share the womb at the same time and consequently share prenatal nutrition provided by the mother's dietary intake. When preparing for labour, twins compete for the best position. This suboptimal intrauterine environment may lead to prematurity, low birth weight and lower weight-forgestational age, 7 which in turn in several cases have been associated with low childhood IQ. 8--12 Apart from a general suboptimal intrauterine environment for b