Wechsler Subtest Patterns of Mentally Retarded Groups: Relationship to g and to Estimates of Heritability

Wechsler Subtest Patterns of Mentally Retarded Groups: Relationship to g and to Estimates of Heritability


E.R. Johnstone Training and Research Center

From a survey of published data on the Wechsler subtest performance of primarily mild and borderline mentally retarded persons, 4304 protocols from 4004 individuals were collated and their subtest patterns on the WAIS, WAIS-R, WISC, and WISC-R were compared. Rank order correlations of subtest scores on the different scales were statistically reliable for all but the WAIS/WAIS-R comparison. On all but the WAIS, reliable inverse relationships were found between subtest performance and the subtests’ g-loadings, indicating that mildly retarded groups tend to score relatively lower on subtests that are better measures of general intelligence. Likewise, reliable and marginally reliable inverse relationships were found between subtest patterns of retarded groups and the subtests’ estimated indexes of heritability, raising the possibility that inherited capacities differentially influence the pattern of performance of these groups.

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Measurement Invariance in Confirmatory Factor Analysis: An Illustration Using IQ Test Performance of Minorities

Measurement Invariance in Confirmatory Factor Analysis: An Illustration Using IQ Test Performance of Minorities

Jelte M. Wicherts and Conor V. Dolan, University of Amsterdam (2010)

Measurement invariance with respect to groups is an essential aspect of the fair use of scores of intelligence tests and other psychological measurements. It is widely believed that equal factor loadings are sufficient to establish measurement invariance in confirmatory factor analysis. Here, it is shown why establishing measurement invariance with confirmatory factor analysis requires a statistical test of the equality over groups of measurement intercepts. Without this essential test, measurement bias may be overlooked. A re-analysis of a study by Te Nijenhuis, Tolboom, Resing, and Bleichrodt (2004) on ethnic differences on the RAKIT IQ test illustrates that ignoring intercept differences may lead to the conclusion that bias of IQ tests with respect to minorities is small, while in reality bias is quite severe.

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Explanation behind the non-g gains in the Flynn Effect : Introducing the measurement invariance model

The phenomenon known as secular IQ gains, or Flynn Effect, is sometimes or perhaps even regularly, viewed as a reason to expect the disappearance of the black-white IQ gap. Not only the logic behind this line of reasoning is a pure non sequitur, it is also disconcerting that the question of g (loadings) and measurement invariance (equivalence) seems to have been underdiscussed.

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Des arguments fallacieux dans le débat Race-QI : Some misleading arguments in the Race-IQ debate

The english text is in bold.

Plus souvent que l’inverse, je remarque que les arguments ad hoc viennent des environnementalistes, qui posent l’idée que les différences raciales n’ont pas de composantes génétiques (substantielles). Nous allons voir à quoi ces arguments ressemblent et pourquoi ils ne fonctionnent pas.

More often than not, I notice that ad hoc arguments seem to come from the environmentalists, which posit than group differences have no (substantial) genetic components. We will see what those arguments look like and why they are bogus.

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The Causes of Group Differences in Intelligence Studied Using the Method of Correlated Vectors and Psychometric Meta-Analysis

The Causes of Group Differences in Intelligence Studied Using the Method of Correlated Vectors and Psychometric Meta-Analysis

Daniel Metzen, Master thesis, 2012.


The huge IQ gap between non-Western immigrants and ethnic Dutch has emerged as one of the primary explanations for the large differences in school and work achievement between these groups. Is there a genetic component in the IQ gap between immigrants and ethnic Dutch? Meta-analyses have shown that the group differences on IQ subtests correlate almost perfectly with the cognitive complexity of these subtests; moreover, the cognitive complexity correlates perfectly with heritability and strongly with physical characteristics of the brain. If no other causes for IQ differences show a strong correlation with g loadings, this would point to a strong genetic component in IQ differences between immigrants and ethnic Dutch. In the present study, we first seek support for the hypothesis that only variables under genetic influence show a strong positive relationship with general intelligence. These are group differences, heritability, and physical characteristics of the brain. Second, we test whether differences in IQ due to variables not under genetic influence, namely biological-environmental factors, aging, and autism show a negligible to weak correlation with general intelligence. Support for both hypotheses would suggest that group differences are primarily driven by genetic factors and only to a minor extent by non-genetic factors. Therefore, group differences between non-Western immigrants and ethnic Dutch should be regarded as stable over time.

Concerning the first analysis, we first conducted a full-fledged meta-analysis on reaction time differences between Whites and higher-IQ groups, and Whites and lower-IQ groups, and we conducted several bare-bones meta-analyses and analyses of individual studies on differences in IQ profile between groups of different ethnicity. Second, we explored subgroups on school type, and religion. Third, we carried out a meta-analysis on the question whether g-loadedness of reaction time measures predicted the heritability of these measures. Fourth, we carried out a meta-analysis on the link between g loadings and brain volume. Concerning the second analysis, we first conducted several bare-bones meta-analyses and analyses of individual studies on biological-environmental variables. Second, we conducted bare-bones meta-analyses on the psychological phenomena autism and aging.

The hypothesis was strongly supported: heritabilities and most group differences showed moderate to strong positive correlations with g, but the correlation of brain volume with g was quite modest. All other phenomena showed no strong positive correlation with g.

It is concluded that these findings are strongly in line with a substantial genetic component in group differences in intelligence. This suggest that the large group differences in school achievement and work achievement are stable and that I/O psychologists should find ways to deal with them instead of ways of trying to change them.

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Four psychometric meta-analyses on the relation of lead level, breastfeeding, and prenatal cocaine and smoke exposure with general intelligence

Are differences in IQ scores also differences in general intelligence? Four psychometric meta-analyses on the relation of lead level, breastfeeding, and prenatal cocaine and smoke exposure with general intelligence

Jan Smit, Master thesis, 2011.


The central question addressed in this study is whether some potential biological and environmental factors might cause true differences in general mental ability (g) between groups, or just “hollow” score differences between groups.

Four bare-bones psychometric meta-analyses (MAs) were performed to test these premises. We predicted strong positive correlations between vectors of lowered IQ scores following lead exposure, prenatal cocaine exposure, and prenatal smoke exposure on the one hand; and vectors of g loadings on the other hand. We also predicted a strong positive correlation between the vector of increased IQ scores following breastfeeding on the one hand and vectors of g loadings on the other hand.

In line with our hypotheses, the meta-analyses showed correlations of .79 on breastfeeding (total N=7847) and .91 on prenatal cocaine exposure (total N=391). However, the variance explained by artifactual errors is too low to draw strong conclusions about the link between cocaine exposure and g, and about the link between breastfeeding and g. Contrary to our hypotheses, the meta-analyses showed correlations of -.19 on lead exposure (total N = 702) and -.19 on prenatal smoke exposure (total N = 443). We were not able to come up with strong theoretical explanations for these values of the correlation between lead exposure and g.

In sum, two of the four meta-analyses showed mixed support for the theory: high correlations between g loadings and effects, but little variance explained in the data points in the meta-analysis. The other two meta-analyses showed no support at all for the theory: an absence of correlations between g loadings and effects and virtually no variance in the data points explained. The amount of support for the theory in these four meta-analyses is therefore modest.

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Haplogroups as evolutionary markers of cognitive ability

Haplogroups as evolutionary markers of cognitive ability

Heiner Rindermann, Michael A. Woodley, James Stratford (2012)

Studies investigating evolutionary theories on the origins of national differences in intelligence have been criticized on the basis that both national cognitive ability measures and supposedly evolutionarily informative proxies (such as latitude and climate) are confounded with general developmental status. In this study 14 Y chromosomal haplogroups (N=47 countries) are employed as evolutionary markers. These are (most probably) not intelligence coding genes, but proxies of evolutionary development with potential relevance to cognitive ability. Correlations and regression analyses with a general developmental indicator (HDI) revealed that seven haplogroups were empirically important predictors of national cognitive ability (I, R1a, R1b, N, J1, E, T[+L]). Based on their evolutionary meaning and correlation with cognitive ability these haplogroups were grouped into two sets. Combined, they accounted in a regression and path analyses for 32–51% of the variance in national intelligence relative to the developmental indicator (35–58%). This pattern was replicated internationally with further controls (e.g. latitude, spatial autocorrelation etc.) and at the regional level in two independent samples (within Italy and Spain). These findings, using a conservative estimate of evolutionary influences, provide support for a mixed influence on national cognitive ability stemming from both current environmental and past environmental (evolutionary) factors.

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WISC-R Subscale Patterns of Abilities of Blacks and Whites Matched on Full Scale IQ

WISC-R Subscale Patterns of Abilities of Blacks and Whites Matched on Full Scale IQ

Cecil R. Reynolds
Texas A & M University

Arthur R. Jensen
University of California, Berkeley

Journal of Educational Psychology 1983, Vol. 75, No. 2, 207-214

Groups of 270 black and 270 white children drawn from the national stratified random sample used in the standardization of the Wechsler Intelligence Scale for Children—Revised (WISC-R) were matched on age, sex, and WISC-R Full-Scale IQ to facilitate investigation of the patterns of specific cognitive abilities, as measured by the 12 subtests of the WISC-R, between the two racial groups. Multivariate analysis of the patterns of subtest differences between whites and blacks and group comparisons on three orthogonalized factor scores (verbal, performance, memory) show small but reliable average white-black differences in patterns of ability. The IQ-matched racial groups show no significant difference on the verbal factor; whites exceed blacks on the performance (largely spatial visualization) factor; blacks exceed whites on the memory factor.

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Occupation and income related to psychometric g

Occupation and income related to psychometric g

Helmuth Nyborg, Arthur R. Jensen, 2001.


The regressions of occupational status and income on psychometric g factor scores were examined in large samples of White (W) and Black (B) American armed forces veterans in their late 30s and who are fairly representative of the population of employed W and B males. These results indicate that when Bs and Ws are matched on g scores, there is no evidence of discrimination unfavorable to Bs for job status at any level of g. Nor are Bs with the same g scores as Ws disadvantaged in income when they are above the median level of g in the total sample. In fact, on both variables – job status and income – Ws turn out to be the relatively more disadvantaged group when the level of g is taken into account.

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The Social Costs of Pornography


A Statement of Findings and Recommendations

Mary Eberstadt and Mary Anne Layden, 2010.


SINCE THE BEGINNING OF THE INTERNET AGE, pornography has been consumed in greater quantities than ever before in human history, and its content has grown more graphic. Recent research suggests that pornography consumption — especially consumption of a more hard-core or violent sort — has negative effects on individuals and society. More studies are necessary, but a growing body of research strongly suggests that for some users pornography can be psychologically addictive, and can negatively affect the quality of interpersonal relationships, sexual health and performance, and social expectations about sexual behavior. Widespread pornography consumption appears to pose a serious challenge to public health and to personal and familial well-being. With concerted action from legislators, the therapeutic community, educators, policymakers, and responsible corporate leaders, however, some of the negative effects of pornography consumption can be combated.

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