Thirty years of research on race differences in cognitive ability.

The culture-only (0% genetic-100% environmental) and the hereditarian (50% genetic-50% environmental) models of the causes of mean Black-White differences in cognitive ability are compared and contrasted across 10 categories of evidence: the worldwide distribution of test scores, g factor of mental ability, heritability, brain size and cognitive ability, transracial adoption, racial admixture, regression, related life-history traits, human origins research, and hypothesized environmental variables. The new evidence reviewed here points to some genetic component in Black-White differences in mean IQ. The implication for public policy is that the discrimination model (i.e., Black-White differences in socially valued outcomes will be equal barring discrimination) must be tempered by a distributional model (i.e., Black-White outcomes reflect underlying group characteristics). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Correction to Rushton and Jensen (2005).

Reports an error in the original article by J. Philippe Rushton and Arthur R. Jensen (Psychology, Public Policy, and Law, 2005[Jun], Vol 11[2], pp. 235-294). An equation on p. 271 was incorrect. In the note to Table 5 on p. 273, a similar equation was incorrect. Finally, on p. 274, the last line of the first paragraph was incorrect. Corrections are published here. (The following abstract of this article originally appeared in record 2005-03637-001.) The culture-only (0% genetic-100% environmental) and the hereditarian (50% genetic-50% environmental) models of the causes of mean Black-White differences in cognitive ability are compared and contrasted across 10 categories of evidence: the worldwide distribution of test scores, g factor of mental ability, heritability, brain size and cognitive ability, transracial adoption, racial admixture, regression, related life-history traits, human origins research, and hypothesized environmental variables. The new evidence reviewed here points to some genetic component in Black-White differences in mean IQ. The implication for public policy is that the discrimination model (i.e., Black-White differences in socially valued outcomes will be equal barring discrimination) must be tempered by a distributional model (i.e., Black-White outcomes reflect underlying group characteristics). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

What if the hereditarian hypothesis is true?

J. P. Rushton and A. R. Jensen (see record 2005-03637-001) review 10 bodies of evidence to support their argument that the long-standing, worldwide Black-White average differences in cognitive ability are more plausibly explained by their hereditarian (50% genetic causation) theory than by culture-only (0% genetic causation) theory. This commentary evaluates the relevance of their evidence, the overall strength of their case, the implications they draw for public policy, and the suggestion by some scholars that the nation is best served by telling benevolent lies about race and intelligence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

There are no public-policy implicatons: A reply to Rushton and Jensen (2005).

J. P. Rushton and A. R. Jensen (see record 2005-03637-001) purport to show public-policy implications arising from their analysis of alleged genetic bases for group mean differences in IQ. This article argues that none of these implications in fact follow from any of the data they present. The risk in work such as this is that public-policy implications may come to be ideologically driven rather than data driven, and to drive the research rather than be driven by the data. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The cultural malleability of intelligence and its impact on the racial/ethnic hierarchy.

This commentary highlights previous literature (see record 2005-03637-001) focusing on cultural and environmental explanations for the racial/ethnic group hierarchy of intelligence. Assumptions underlying definitions of intelligence, heritability/genetics, culture, and race are noted. Historical, contextual, and testing issues are clarified. Specific attention is given to studies supporting stereotype threat, effects of mediated learning experiences, and relative functionalism. Current test development practices are critiqued with respect to methods of validation and item development. Implications of the genetic vs. culture-only arguments are discussed with respect to the malleability of IQ. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A reexamination of black-white mean differences in work performance: More data, more moderators.

This study is the largest meta-analysis to date of Black-White mean differences in work performance. The authors examined several moderators not addressed in previous research. Findings indicate that mean racial differences in performance favor Whites (d = 0.27). Effect sizes were most strongly moderated by criterion type and the cognitive loading of criteria, whereas data source and measurement level were influential moderators to a lesser extent. Greater mean differences were found for highly cognitively loaded criteria, data reported in unpublished sources, and for performance measures consisting of multiple item scales. On the basis of these findings, the authors hypothesize several potential determinants of mean racial differences in job performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The IQ paradox is still resolved: Reply to Loehlin (2002) and Rowe and Rodgers (2002).

In their original article (W. T. Dickens & J. R. Flynn, 2001), the authors formalized the consensus model of reciprocal effects between IQ and environment and showed that it can resolve the apparent paradox between high heritability and large environmental effects. Commentators suggested that the model has undesirable properties that call its usefulness into question. J. L. Loehlin (2002) argued that incorporating persistence of IQ into the model causes problematic behavior. D. C. Rowe and J. L. Rodgers (2002) argued that an increasing correlation of IQ and environment should have caused growing variance of IQ. Empirical evidence suggests that IQ is not sufficiently persistent to cause the problems Loehlin found and that the correlation of IQ and environment has not grown much over time so that the reciprocal effects model need not imply increasing variance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sleep spindles and learning potential.

The number of sleep spindles remains relatively stable within individuals from night to night. However, there is little explanation for the large interindividual differences in spindles. The authors investigated the relationship between spindles and intelligence quotient (IQ) in 3 separate studies. The number of spindles and sigma power were positively correlated with performance IQ (PIQ), but not verbal IQ (VIQ). The perceptual/analytical skills measured by the PIQ Picture Completion subscale accounted for most of the interindividual differences in spindles. Furthermore, there was a relationship between the rapid eye movements (REMs) of REM sleep and VIQ in individuals with higher IQ scores. A similar pattern was observed between spindles and PIQ. It was hypothesized that high-IQ individuals have more spindles that can support more complex cortical networks underlying perceptual/analytical abilities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Wanted: More race realism, less moralistic fallacy.

Despite repeated claims to the contrary, there has been no narrowing of the 15- to 18-point average IQ difference between Blacks and Whites (1.1 standard deviations); the differences are as large today as they were when first measured nearly 100 years ago. They, and the concomitant difference in standard of living, level of education, and related phenomena, lie in factors that are largely heritable, not cultural. The IQ differences are attributable to differences in brain size more than to racism, stereotype threat, item selection on tests, and all the other suggestions given by the commentators. It is time to meet reality. It is time to stop committing the "moralistic fallacy" that good science must conform to approved outcomes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

IQ gains and fluid g.

Responds to J. P. Rushton's comments (see record 2000-15413-003) on the J. R. Flynn article (see record 1999-00167-001) examining IQ gains over time. Flynn contends that factor analysis does show that inbreeding depression isolated from a cluster including fluid g, IQ gains, and Black-White differences. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Under the Skin: On the Impartial Treatment of Genetic and Environmental Hypotheses of Racial Differences.

Environmental and genetic explanations have been given for Black-White racial differences in intelligence and other traits. In science, viable, alternative hypotheses are ideally given equal Bayesian prior weights; but this has not been true in the study of racial differences. This article advocates testing environmental and genetic hypotheses of racial differences as competing hypotheses. Two methods are described: (a) fitting means within structural equation models and (b) predicting means of interracial children. These methods have limitations that call for improved research designs of racial differences. One improvement capitalizes on biotechnology. Genetic admixture estimates--the percentage of genes of European origin that a Black individual possesses (independent of genes related to skin coloration)--can represent genetic influences. The study of interracial children can be improved by increasing sample size and by choosing family members who are most informative for a research question. Eventually, individual-admixture estimates will be replaced by molecular genetic tests of alleles of those genes that influence traits. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Attention problems, inhibitory control, and intelligence index overlapping genetic factors: A study in 9-, 12-, and 18-year-old twins.

It is assumed that attention problems (AP) are related to impaired executive functioning. We investigated the association between AP and inhibitory control and tested to what extent the association was due to genetic factors shared with IQ. Data were available from 3 independent samples of 9-, 12-, and 18-year-old twins and their siblings (1,209 participants). AP were assessed with checklists completed by multiple informants. Inhibitory control was measured with the Stroop Color Word Task (Stroop, 1935), and IQ with the Wechsler Intelligence Scale for Children (Wechsler et al., 2002) or Wechsler Adult Intelligence Scale (Wechsler, 1997). AP and inhibitory control were only correlated in the 12-year-old cohort (r = .18), but appeared non-significant after controlling for IQ. Significant correlations existed between AP and IQ in 9- and 12-year olds (r = ?.26/–.34). Inhibitory control and IQ were correlated in all cohorts (r = ?.16, ?.24 and ?.35, respectively). Genetic factors that influenced IQ also influenced inhibitory control. We conclude that the association between AP and inhibitory control as reported in the literature may largely derive from genetic factors that are shared with IQ. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Are black-white differences in females' body dissatisfaction decreasing? A meta-analytic review.

Proponents of the sociocultural model of eating disorders have suggested that ethnic differences in body dissatisfaction may be diminishing as the thin ideal of beauty becomes more widely disseminated among minority women. In a meta-analysis, the authors examined temporal trends in Black-White differences and also examined whether these differences generalize across various age groups and measures. Results confirmed more favorable body image evaluations among Black than White females, with the greatest differences at the age period of the early 20s. Although results confirmed that ethnic differences have diminished, this trend was limited to weight-focused measures. On more global body image measures, ethnic differences actually increased. These results suggest that the relationship between Black-White ethnicity and body image is more complex than previously suggested. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ethnic and gender subgroup differences in assessment center ratings: A meta-analysis.

Assessment centers are widely believed to have relatively small standardized subgroup differences (d). However, no meta-analytic review to date has examined ds for assessment centers. The authors conducted a meta-analysis of available data and found an overall Black-White d of 0.52, an overall Hispanic-White d of 0.28, and an overall male-female d of -0.19. Consistent with our expectations, results suggest that Black-White ds in assessment center data may be larger than was previously thought. Hispanic-White comparisons were smaller than were Black-White comparisons. Females, on average, scored higher than did males in assessment centers. As such, assessment centers may be associated with more adverse impact against Blacks than is portrayed in the literature, but the predictor may have less adverse impact and be more "diversity friendly" for Hispanics and females. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Flynn effects not genetic and unrelated to race differences.

Comments on the article by J. R. Flynn (see record 1999-00167-001) which argued that massive IQ gains over time test the IQ-intelligence equation, reveal groups who achieve far beyond their mean IQ's and falsify prominent arguments for a genetic racial IQ gap. The author contends that Flynn fails to report in sufficient detail a summary of what the gains over time do and do not tell us about the nature of the Black–White difference. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Tethering the elephant: Capital cases, IQ, and the Flynn effect.

Capital offenders cannot be executed if they are mentally retarded. Therefore, the IQ scores of offenders are important, and the U.S. 4th Circuit Court of Appeals has held that the Flynn effect is relevant to interpreting their IQ scores. The Flynn effect (IQ gains over time) means that different IQ tests will give different scores purely as a result of when the tests were normed. Because execution must not be a random result of what test defendants take, a formula is provided to convert IQ scores to a common metric: the norms current at the time the test was taken. The formula also includes a correction based on evidence that the Wechsler Adult Intelligence Scale-Third Edition inflates IQs because of sampling error. Given the inevitability that opposing experts will offer conflicting diagnoses, IQ scores merit special attention in capital cases. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Utility of socioeconomic status as a control in racial comparisons of IQ.

F. K. Trotman (see record 1978-06591-001) has presented evidence indicating that Black and White families equated in terms of socioeconomic status differ widely in terms of R. Wolf's (1964) measure of intellectual home environment. On the basis of this evidence, Trotman has drawn a variety of conclusions about the nonutility of socioeconomic status as a control in racial comparisons of IQ. In this article, the validity of Trotman's conclusions are called into question by a critique of her methodology and a critical examination of her results. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Motivation, race, social class, and IQ.

Administered the Performance subscales of the WISC to 208 male and 208 female junior and senior high school students (aged 12-16 yrs) to test the prediction that if performance responded to the manipulation of the testee's motivation state, the size of interracial differences in mean IQ would be more flexible than was suggested by A. R. Jensen's (1969) review of the literature. The variables of test atmosphere (evaluative or gamelike), tester expectation (high or low), race of tester (Black or White), and race of S (Black or White) were manipulated. The pattern of mean IQ scores as well as self-ratings of mood indicated that test performance was optimal at moderate levels of motivational arousal. A replication of the experiment employing 208 male Ss increased cell sizes to the point that socioeconomic status could be treated as an independent variable. Results suggested that interracial differences in mean IQ might be erased depending upon the social psychological characteristics of the test setting and the socioeconomic background of the testee. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Heterosis doesn't cause the Flynn effect: A critical examination of Mingroni (2007).

Mingroni (see record 2007-10421-011) proposed that heterosis or hybrid vigor may be the principal driver of the Flynn effect—the tendency for IQ scores to increase at a rate of approximately 3 points per decade. This model was presented as a resolution to the IQ paradox—the observation that IQ scores have been increasing despite their high adult heritability—on the basis that substantial changes in IQ can only be accounted for by changes in underlying genetic factors. It is here argued that this model is predicated upon a misconception of the Flynn effect, which is most pronounced on the least g-loaded components of cognitive ability tests and is uncorrelated with genetic effects such as inbreeding depression scores (which are correlated with the g loadings of tests). Evidence supportive of the recently proposed life history model of the Flynn effect is presented. In the discussion, other theoretical objections to the heterosis model are also considered. On this basis, it is concluded that the Flynn effect is strongly entwined with developmental status and that heterosis cannot be its principal cause. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Expanding variance and the case of historical changes in IQ means: A critique of Dickens and Flynn (2001).

The Flynn effect is the rise in mean IQ scores during the 20th century, amounting to about 0.33 IQ points per year. Many theoretical explanations have been proposed, though none are universally accepted. W. Dickens and J. R. Flynn's (2001) new approach explains the large IQ changes by means of recursive models of IQ growth. A salient feature of their models is that IQ phenotypes and their supportive environments are correlated; in addition, environmental effects can rebound on phenotypic IQ to increase or lower IQ. In this critique, the authors examine an empirical challenge to their models, which typically imply large changes in IQ variance. However, the historical rise in IQ mean level has not been accompanied by substantial variance changes, a finding inconsistent with the properties of the proposed model. (PsycINFO Database Record (c) 2010 APA, all rights reserved)