School-level genetic variation predicts school-level verbal IQ scores: Results from a sample of American middle and high schools

School-level genetic variation predicts school-level verbal IQ scores: Results from a sample of American middle and high schools

Kevin M. Beaver, John Paul Wright (2011)


Research has consistently revealed that average IQ scores vary significantly across macro-level units, such as states and nations. The reason for this variation in IQ, however, has remained at the center of much controversy. One of the more provocative explanations is that IQ across macro-level units is the result of genetic differences, but empirical studies have yet to examine this possibility directly. The current study partially addresses this gap in the literature by examining whether average IQ scores across thirty-six schools are associated with differences in the allelic distributions of dopaminergic polymorphisms across schools. Analysis of data drawn from subjects (ages 12–19 years) participating in the National Longitudinal Study of Adolescent Health provides support in favor of this perspective, where variation in school-level IQ scores was predicted by school-level genetic variation. This association remained statistically significant even after controlling for the effects of race.

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Transracially adopted intermediate IQ : Hereditarian nonsense

A bad, invalid argument commonly used by hereditarians is the research concerning transracial adoption. The claim usually made is that black, black-white mixed-race, white, asian-white mixed-race adoptees had IQs following the well-established genetic hierarchy seemingly B < BW < W < AW.

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Specific Aptitude Theory Revisited: Is There Incremental Validity for Training Performance?

Specific Aptitude Theory Revisited: Is There Incremental Validity for Training Performance?

Kenneth G. Brown, Huy Le and Frank L. Schmidt
University of Iowa


There has been controversy over the years about whether specific mental abilities increment validity for predicting performance above and beyond the validity for general mental ability (GMA). Despite its appeal, specific aptitude theory has received only sporadic empirical support. Using more exact statistical and measurement methods and a larger data set than previous studies, this study provides further evidence that specific aptitude theory is not tenable with regard to training performance. Across 10 jobs, differential weighting of specific aptitudes and specific aptitude tests were found not to improve the prediction of training performance over the validity of GMA. Implications of this finding for training research and practice are discussed.

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Flynn contra Rushton on principal component analysis : A failed replication

While Rushton (1999) demonstrates, using PCA, that g and black-white differences were related, with Flynn Effect (FE) gains over time showing no relationship with the aforementioned variables, Flynn (2000) has challenged Rushton in arguing that Wechsler’s subtest loadings on the Raven test, an universally recognized measure of fluid g, showed positive correlations with both black-white differences and FE gains. Up to now, Flynn’s estimates of g fluid (Gf) has not been scrutinized. I will show presently that the Flynn’s g-fluid (call it, fluid reasoning) and Rushton’s g-crystallized (call it, consolidated knowledge) anomaly was solely due to a single statistical artifact, namely, g_Fluid vector unreliability. By adding additional samples, I created a new, updated Wechsler’s subtest Gf loadings. The present analysis comes to the conclusion that g_Fluid was not in fact correlated with FE gains. Furthermore, this Gf variable has been correlated with other variables as well, such as, heritability (h2), shared environment (c2), nonshared environment (e2), adoption IQ gains, inbreeding depression (ID), and mental retardation (MR). I will also discuss these findings in light of Kan’s (2011) thesis against the hereditarian hypothesis.

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IQ Testing : From Correlation to Causation

It is well known and acknowledged that IQ correlates with social outcomes (Herrnstein & Murray, 1994; Jensen, 1998; Gottfredson, 1997), measures of health (Gottfredson, 2003, & Deary, 2004; Reeve & Basalik, 2010), wages (Jones & Schneider, 2008), savings (Jones, 2012), job performance (Ree & Earles, 1994; Hunter & Schmidt, 2004), training success (Ree & Earles, 1991), general knowledge (Reeve, 2004), general economic peformance (Jones & Schneider, 2006; Jones, 2011, 2012; Hafer & Jones, 2012; Meisenberg, 2012; Kalonda-Kanyama & Kodila-Tedika, 2012), and this, without mentioning other many correlates of importance (Lynn & Vanhanen, 2012). But IQ critics usually claim that correlational studies tell us nothing about the causal link. The present article will introduce some research on this topic.

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Les tests QI, de corrélation à causalité

S’il est aujourd’hui bien admis et reconnu que le QI corrèle avec les résultats socio-économiques (Herrnstein & Murray, 1994; Jensen, 1998; Gottfredson, 1997), les indices et mesures de santé (Gottfredson, 2003, & Deary, 2004; Reeve & Basalik, 2010), le salaire (Jones & Schneider, 2008), l’épargne (Jones, 2012), la performance au travail (Ree & Earles, 1994), la performance dans les cours de formation (Ree & Earles, 1991), les connaissances générales (Reeve, 2004), la performance économique générale (Jones & Schneider, 2006; Jones, 2011, 2012; Hafer & Jones, 2012; Meisenberg, 2012; Kalonda-Kanyama & Kodila-Tedika, 2012), et ceci, sans mentionner d’autres corrélats bien évidents (Lynn & Vanhanen, 2012), les critiques continuent à affirmer que la causalité n’est pas prouvée pour autant. Le présent article s’attèle à présenter l’état des recherches actuelles sur le sujet.

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Path Analysis of IQ during Infancy and Early Childhood and an Index of the Home Environment in the Colorado Adoption Project

Path Analysis of IQ during Infancy and Early Childhood and an Index of the Home Environment in the Colorado Adoption Project

University of Colorado, Boulder

Pennsylvania State University

INTELLIGENCE 12, 27-45 (1988)

A parent-offspring adoption path model, which includes a measured index of the home environment, was formulated to assess the extent to which relationships between the environmental index and children’s behavior are mediated by genetic and environmental influences of the parents. In addition to the direct effect of the home environment on children’s behavior, three types of indirect effects mediated by parental phenotype are considered: a pure environmental effect, a pure genetic effect, and a combined environmental-genetic effect. To illustrate its application, the model was fitted to parental and offspring IQ data collected in the Colorado Adoption Project and an environmental index based on Caldwell and Bradley’s (1978) Home Observation for Measurement of the Environment (HOME). Four sets of data, including the HOME index and offspring IQ measured longitudinally at 1, 2, 3, and 4 years of age, were analyzed. The results suggest that in infancy (ages 1 and 2), the HOME reveals a direct environmental effect on children’s IQ as well as indirect effects mediated via parental IQ. Surprisingly, during early childhood (ages 3 and 4), the relationship between the HOME and children’s IQ is due only to indirect parental mediation. Moreover, other than at year 1, the mediation is purely genetic.

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Investigation of the relationship between mental retardation with heritability and environmentality of the Wechsler subtests

The present analysis is an extension of Spitz’s earlier (1988) study on the relationship between mental retardation (MR) lower score and subtest heritability (h2) and g-loadings. These relationships were found to be positive. But Spitz himself haven’t tested the possibility that MR (lower) score could be related with shared (c2) or nonshared (e2) environment. I use the WAIS and WISC data given in my earlier post, and have found that MR is not related with c2 and e2 values. These findings nevertheless must be interpreted very carefully because the small number of subtests (e.g., 10 or 11) is a very critical limitation.

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Méta-analyse des corrélations entre le facteur g et les indices d’héritabilité et environnementalité des sous-tests de QI

Il existe aujourd’hui assez peu de tests ayant investi la question de la relation entre le facteur g et l’héritabilité. Herman Spitz (1988) est probablement l’un des premiers connus à avoir tenté un tel test. Rijsdijk (2002) également démontre une telle relation. La seule méta-analyse connue à ce jour vient de van Bloois et al. (2009, p. 61) malgré le fait qu’elle soit encore restée non publiée. Quoi qu’il en soit, aucun n’avait semble-t-il tenté de tester un possible lien entre facteur g et environnement partagé ou non-partagé. Il aurait peut-être été problématique pour la théorie héréditariste si la corrélation entre g et l’héritabilité (h2) est équivalente à celle entre g et l’environnement, partagé (c2) ou non partagé (e2), sauf si ladite théorie fournit l’explication au phénomène. Rushton (2007) a été peut-être le seul à le tenter, bien qu’utilisant un tout autre test QI, les matrices progressive de Raven. La corrélation entre g et h2 était positive mais plus faible qu’entre g et e2, bien que g et c2 corrélait à zéro. L’échantillon de jumeaux utilisé par Rushton était néanmoins assez faible. La présente analyse s’attèle donc à présenter des résultats méta-analytiques.

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The Malleability of IQ as Judged From Adoption Studies

The Malleability of IQ as Judged From Adoption Studies

Charles Locurto (1990)
College of the Holy Cross

Estimates of the malleability of IQ depend largely upon the results of adoption studies. Moderate estimates presently range between 20 to 25 points. It is here argued that the standard adoption study in fact provides little unequivocal evidence of IQ’s malleability. Further, the most prominent adoption studies of contrasted environments, studies wherein the biological family’s socioeconomic status is clearly different from that of the adoptive family, provide malleability estimates that are more modest than has been claimed elsewhere.

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