Males have greater g: Sex differences in general mental ability from 100,000 17- to 18-year-olds on the Scholastic Assessment Test

Factorial Invariance of the Anadolu Sak Intelligence Scale Across Gender

The purpose of this study was to examine the factorial invariance of the ASIS (Anadolu Sak Intelligence Scale) across gender. Raw scores from the ASIS standardization study ( N = 4641) were used in the analyses. Factorial invariance was analyzed by gender across three age groups: 4–7 ( N = 2528), 8–9 ( N = 848), and 10–12 ( N = 1265) using the Multisample Confirmatory Factor Analysis. Six models were developed from unconstrained to more constrained to test the factorial invariance. Each model tested one hypothesis. The findings showed that the second-order g model of the ASIS was invariant in all age groups. In addition, the first-order and second-order factor loadings and g variance were invariant across gender. A partial subtest intercept invariance was found for ages 4–7. Findings imply that ASIS factor scores mean the same latent variable for boys and girls in different age groups.

The Impasse on Gender Differences in Intelligence: a Meta-Analysis on WISC Batteries

This meta-analysis reviews 79 studies (N = 46,605) that examined the existence of gender difference on intelligence in school-aged children. To do so, we limited the literature search to works that assessed the construct of intelligence through the Wechsler Intelligence Scales for Children (WISC) batteries, evaluating eventual gender differences in indices and subtests. The theoretical framework we adopted is the cross-battery approach which locates cognitive abilities into different levels, also considering the possible mediating effect of the version of the WISC being used. As for broad abilities, a notable discrepancy emerged in favour of males for visual and crystallized intelligence, while female/male differences on fluid intelligence were negligible. Conversely, females’ performance on the processing speed factor was superior. Interesting results emerged at the subtest levels, albeit with less pronounced differences in performance. Results generally showed that older versions of WISC batteries displayed larger gender differences compared to the most recent ones.

The sexual brain, genes, and cognition: A machine-predicted brain sex score explains individual differences in cognitive intelligence and genetic influence in young children

Sex impacts the development of the brain and cognition differently across individuals. However, the literature on brain sex dimorphism in humans is mixed. We aim to investigate the biological underpinnings of the individual variability of sexual dimorphism in the brain and its impact on cognitive performance. To this end, we tested whether the individual difference in brain sex would be linked to that in cognitive performance that is influenced by genetic factors in prepubertal children (N = 9,658, ages 9-10 years old; the Adolescent Brain Cognitive Development study). To capture the interindividual variability of the brain, we estimated the probability of being male or female based on the brain morphometry and connectivity features using machine learning (herein called a brain sex score). The models accurately classified the biological sex with a test ROC-AUC of 93.32%. As a result, a greater brain sex score correlated significantly with greater intelligence (p_fdr  < .001, η p 2 $$ {\eta}_p^2 $$  = .011-.034; adjusted for covariates) and higher cognitive genome-wide polygenic scores (GPSs) (p_fdr  < .001, η p 2 $$ {\eta}_p^2 $$  < .005). Structural equation models revealed that the GPS-intelligence association was significantly modulated by the brain sex score, such that a brain with a higher maleness score (or a lower femaleness score) mediated a positive GPS effect on intelligence (indirect effects = .006-.009; p = .002-.022; sex-stratified analysis). The finding of the sex modulatory effect on the gene-brain-cognition relationship presents a likely biological pathway to the individual and sex differences in the brain and cognitive performance in preadolescence.

Age and Sex Invariance of the Woodcock-Johnson IV Tests of Cognitive Abilities: Evidence from Psychometric Network Modeling

The Woodcock-Johnson IV Tests of Cognitive Abilities (WJ IV COG) is a comprehensive assessment battery designed to assess broad and narrow cognitive abilities, as defined by the Cattell-Horn-Carroll (CHC) theory of intelligence. Previous studies examined the invariance of the WJ assessments across sex and age groups using factor analytic methods. Psychometric network modeling is an alternative methodology that can address both direct and indirect relationships among the observed variables. In this study, we employed psychometric network modeling to examine the invariance of the WJ IV COG across sex and age groups. Using a normative sample (n = 4212 participants) representative of the United States population, we tested the extent to which the factorial structure of the WJ IV COG aligned with CHC theory for the school-aged sample. Next, we used psychometric network modeling as a data-driven method to investigate whether the network structure of the WJ IV COG remains similar across different sex and age (age 6 to 19, inclusively) groups. Our results showed that the WJ IV COG maintained the same network structure across all age and sex groups, although the network structure at younger ages indicated weaker relationships among some subtests. Overall, the results provide construct validity evidence for the WJ IV COG, based on both theoretical and data-driven methods.

Sex differences in school performance as a function of conscientiousness, imagination and the mediating role of problem behaviour

The roles of Conscientiousness and Imagination in explaining sex differences in school performance were examined in two Flemish samples of school children using parental and teacher ratings of school performance (N = 599) and school grades (N = 448). Both personality domains predicted parental ratings of school performance and grades. In one sample, girls received slightly higher parental ratings of language achievement and overall performance ratings by teachers. However, controlling for Conscientiousness and Imagination facets, boys scored slightly higher for math and history. In this sample, lower externalising behaviour partially mediated the relation between Conscientiousness facets and school performance in girls but not in boys, but this pattern was not replicated in the second sample. We concluded that sex differences in school performance were small and many could be accounted for by personality traits. In some cases, however, personality traits acted to amplify sex differences in school performance. Copyright © 2008 John Wiley & Sons, Ltd.

Tests of Scholastic Aptitude Cover Reasoning Facets Sufficiently

Abstract. This study explores how reasoning facets relate to tests of scholastic aptitude and to academic performance. Intelligence test scores and academic aptitude test scores from freshman students in science (n = 284) and economics (n = 359) as well as subsequent grades from their first year in college were used to analyze structural equation models. The direct influence of reasoning facets on academic performance is fully mediated by academic aptitude test scores. Numeric abilities dominate the aptitude tests’ predictive power. Verbal reasoning explains a significant amount of aptitude test score variance in science but not in economics. The mediation analysis suggests that verbal, numeric, and figural reasoning are covered sufficiently by the aptitude tests.

Sex differences in the intellectual functioning of early school-aged children in rural China

Background

Gender disparities in China are concentrated in poor rural areas and among poor households. The difference in intelligence between boys and girls is less clear in rural China. The purpose of this paper was to assess sex differences in the intellectual function of early school-aged children in rural China.

Methods

One thousand seven hundred forty four early school-aged offspring of women who had participated in a prenatal supplementation trial with different combinations of micronutrients and continued to reside in two rural counties in China were followed. We measured their Full-Scale IQ (FSIQ), Verbal Comprehension Index (VCI), Working Memory Index (WMI), Perceptual Reasoning Index (PRI) and Processing Speed Index (PSI) using the Wechsler Intelligence Scale for Children (WISC-IV). Multilevel analyses were used to assess sex differences in intellectual functioning in 7-10-year-old children in rural China.

Results

Boys’ adjusted mean FSIQ score was 0.97 points higher (95 % CI: -2.22 − 0.28) than that of girls. Girls obtained higher mean WMI and PSI scores, with 1.32 points (95 % CI: 0.14 − 2.51) and 3.10 points (95 % CI: 1.82–4.38) higher adjusted means, respectively. Boys’ adjusted mean VCI and PRI scores were significantly higher than those of girls, and the mean differences were 2.44 points (95 % CI: 0.95 − 3.94) and 3.68 points (95 % CI: 2.36 − 5.01), respectively.

Conclusions

There is no evidence to suggest sex differences in the general intelligence of early school-aged children in rural China. However, a difference in general intelligence between 10-year-old boys and girls was evident. Girls and boys in rural China tended to show different specific cognitive abilities.

Meta-analysis of associations between human brain volume and intelligence differences: How strong are they and what do they mean?

Positive associations between human intelligence and brain size have been suspected for more than 150 years. Nowadays, modern non-invasive measures of in vivo brain volume (Magnetic Resonance Imaging) make it possible to reliably assess associations with IQ. By means of a systematic review of published studies and unpublished results obtained by personal communications with researchers, we identified 88 studies examining effect sizes of 148 healthy and clinical mixed-sex samples (>8000 individuals). Our results showed significant positive associations of brain volume and IQ (r=.24, R(2)=.06) that generalize over age (children vs. adults), IQ domain (full-scale, performance, and verbal IQ), and sex. Application of a number of methods for detection of publication bias indicates that strong and positive correlation coefficients have been reported frequently in the literature whilst small and non-significant associations appear to have been often omitted from reports. We show that the strength of the positive association of brain volume and IQ has been overestimated in the literature, but remains robust even when accounting for different types of dissemination bias, although reported effects have been declining over time. While it is tempting to interpret this association in the context of human cognitive evolution and species differences in brain size and cognitive ability, we show that it is not warranted to interpret brain size as an isomorphic proxy of human intelligence differences.

Considerations Relating to the Study of Group Differences in Intelligence

There are signs that the debate over racial and gender differences in intelligence is about to begin again. In this article we will be concerned primarily with racial differences but will make remarks about gender differences where applicable. Previously there have been bitter arguments over whether or not races exist, over whether it is either important or proper to study racial and gender differences in intelligence, and over the conclusions that have been drawn about environmental and genetic causes as determinants of these differences. We argue that races do, indeed, exist and that studying differences in cognitive competence between groups is a reasonable thing to do. We also point out that past research on both racial and gender differences in intelligence has been marked by methodological errors and overgeneralizations by researchers on all sides of the issue. We propose ten principles of design, analysis, and reporting that ought to be considered carefully when doing or evaluating research in this area.

Gender Differences in Child Word Learning

In prior work with adults, women were found to outperform men on a paired-associates word-learning task, but only when learning phonologically-familiar novel words. The goal of the present work was to examine whether similar gender differences in word learning would be observed in children. In addition to manipulating phonological familiarity, referent familiarity was also manipulated. Children between the ages of 5 and 7 learned phonologically-familiar or phonologically-unfamiliar novel words in association with pictures of familiar referents (animals) or unfamiliar referents (aliens). Retention was tested via a forced-choice recognition measure administered immediately after the learning phase. Analyses of retention data revealed stronger phonological and referent familiarity effects in girls than in boys. Moreover, girls outperformed boys only when learning phonologically-familiar novel words and when learning novel words in association with familiar referents. These findings are interpreted to suggest that females are more likely than males to recruit native-language phonological and semantic knowledge during novel word learning.

Beyond Gender Differences

Proponents of what has been termed the Gender Similarities Hypothesis (GSH) have typically relied on meta-analyses as well as the generation of nonsignificant tests of mean differences to support their argument that the genders are more similar than they are different. In the present article, we argue that alternative statistical methodologies, such as tests of equivalence, can provide more accurate (yet equally rigorous) tests of these hypotheses and therefore might serve to complement, challenge, and/or extend findings from meta-analyses. To demonstrate and test the usefulness of such procedures, we examined Scholastic Aptitude Test–Math (SAT-M) data to determine the degree of similarity between genders in the historically gender-stereotyped field of mathematics. Consistent with previous findings, our results suggest that men and women performed similarly on the SAT-M for every year that we examined (1996–2009). Importantly, our statistical approach provides a greater opportunity to open a dialogue on theoretical issues surrounding what does and what should constitute a meaningful difference in intelligence and achievement. As we note in the discussion, it remains important to consider whether even very small but consistent gender differences in mean test performance could reflect stereotype threat in the testing environment and/or gender biases in the test itself that would be important to address.

The Vocabulary and Overclaiming Test (VOC-T)

The present research aimed at constructing a questionnaire measuring overclaiming tendencies (VOC-T-bias) as an indicator of self-enhancement. An approach was used which also allows estimation of a score for vocabulary knowledge, the accuracy index (VOC-T-accuracy), using signal detection theory. For construction purposes, an online study was conducted with N = 1,176 participants. The resulting questionnaire, named Vocabulary and Overclaiming – Test (VOC-T) was investigated with regard to its psychometric properties in two further studies. Study 2 used data from a population representative sample (N = 527), and Study 3 was another online survey (N = 933). Results show that reliability estimates were satisfactory for the VOC-T-bias index and the VOC-T-accuracy index. Overclaiming did not correlate with knowledge, but it was sensitive to self-enhancement supporting the construct validity of the test scores. The VOC-T-accuracy index in turn covaried with general knowledge and even more so with verbal knowledge, which also supports construct validity. Moreover, the VOC-T-accuracy index had a meaningful correlation with age in both validation studies. All in all, the psychometric properties can be regarded as sufficient to recommend the VOC-T for research purposes.

Gender differences in adult word learning

In prior work, women were found to outperform men on short-term verbal memory tasks. The goal of the present work was to examine whether gender differences on short-term memory tasks are tied to the involvement of long-term memory in the learning process. In Experiment 1, men and women were compared on their ability to remember phonologically-familiar novel words and phonologically-unfamiliar novel words. Learning of phonologically-familiar novel words (but not of phonologically-unfamiliar novel words) can be supported by long-term phonological knowledge. Results revealed that women outperformed men on phonologically-familiar novel words, but not on phonologically-unfamiliar novel words. In Experiment 2, we replicated Experiment 1 using a within-subjects design, and confirmed gender differences on phonologically-familiar, but not on phonologically-unfamiliar stimuli. These findings are interpreted to suggest that women are more likely than men to recruit native-language phonological knowledge during novel word-learning.

The brain as a distributed intelligent processing system: an EEG study

Background

Various neuroimaging studies, both structural and functional, have provided support for the proposal that a distributed brain network is likely to be the neural basis of intelligence. The theory of Distributed Intelligent Processing Systems (DIPS), first developed in the field of Artificial Intelligence, was proposed to adequately model distributed neural intelligent processing. In addition, the neural efficiency hypothesis suggests that individuals with higher intelligence display more focused cortical activation during cognitive performance, resulting in lower total brain activation when compared with individuals who have lower intelligence. This may be understood as a property of the DIPS.

Methodology and Principal Findings

In our study, a new EEG brain mapping technique, based on the neural efficiency hypothesis and the notion of the brain as a Distributed Intelligence Processing System, was used to investigate the correlations between IQ evaluated with WAIS (Whechsler Adult Intelligence Scale) and WISC (Wechsler Intelligence Scale for Children), and the brain activity associated with visual and verbal processing, in order to test the validity of a distributed neural basis for intelligence.

Conclusion

The present results support these claims and the neural efficiency hypothesis.

Sex Differences in Verbal and Visual-Spatial Tasks under Different Hemispheric Visual-Field Presentation Conditions

This paper reports sex differences in cognitive task performance that emerged when 39 Australian university undergraduates (19 men, 20 women) were asked to solve verbal (lexical) and visual-spatial cognitive matching tasks which varied in difficulty and visual field of presentation. Sex significantly interacted with task type, task difficulty, laterality, and changes in performance across trials. The results revealed that the significant individual-differences' variable of sex does not always emerge as a significant main effect, but instead in terms of significant interactions with other variables manipulated experimentally. Our results show that sex differences must be taken into account when conducting experiments into human cognitive-task performance.

Whole brain size and general mental ability: a review

We review the literature on the relation between whole brain size and general mental ability (GMA) both within and between species. Among humans, in 28 samples using brain imaging techniques, the mean brain size/GMA correlation is 0.40 (N = 1,389; p < 10⁻¹⁰); in 59 samples using external head size measures it is 0.20 (N = 63,405; p < 10⁻¹⁰). In 6 samples using the method of correlated vectors to distill g, the general factor of mental ability, the mean r is 0.63. We also describe the brain size/GMA correlations with age, socioeconomic position, sex, and ancestral population groups, which also provide information about brain–behavior relationships. Finally, we examine brain size and mental ability from an evolutionary and behavior genetic perspective.

Psychometric analysis of the systemizing quotient (SQ) scale

The psychometric properties of the systemizing quotient (SQ) developed by Baron-Cohen (2003) are investigated in three studies. Furthermore, we examine the notion that the ability to systemize should be independent of intelligence. In Studies 1 and 2, confirmatory factor analyses are used to examine the factor structure of the SQ. Study 3 examines the relationship between systemizing, mental rotation and intelligence. Studies 1 and 2 indicate that the SQ does not possess a unifactorial structure but is best considered as four related factors; Study 3 found that SQ was not related to intelligence, although mental rotation was. A four factor structure using fewer items was a better fit for the data than either the original version of the SQ or Wakabayashi et al.'s (2006) revised version. Overall these results support Baron-Cohen's view that SQ is not related to intelligence. Although mental rotation is correlated to SQ, it is not the main determinant of SQ. The problems of self-report measures are discussed along with the difficulties related to measuring systemizing.