Group Differences In Intelligence Research Articles

Someone who knows and someone I trust: Investigating how and with whom U.S. 8- to 14-year-old youth seek to learn about racial inequality.

This study investigated 8- to 14-year-old U.S. children's (N = 202, 47% girls, and 49% White) evaluations of statements reflecting individual and structural attributions for the causes of racial inequality between Black and White people in the United States, the epistemic characteristics they used to seek out more information on this topic, and who they believed reflected these characteristics. With age, participants increasingly endorsed statements reflecting structural attributions for racial inequality (i.e., educational and occupational exclusion), and increasingly reasoned about privilege and racism. In contrast, participants did not endorse statements reflecting individual attributions at any age (i.e., group differences in intelligence and effort), instead reasoning about equality between racial groups. Overall, participants sought expertise (i.e., content knowledge) and interpersonal trust (i.e., closeness and support) in a scenario where they could choose a discussion partner to learn more about racial inequality, and were most likely to seek out their family members, though some also sought out their friends, teachers, and the internet or social media. This study provides insights into who children see as relevant sources for learning about racial inequality and their reasons for trusting them. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Race, Ethnicity, and the Scarr-Rowe Hypothesis: A Cautionary Example of Fringe Science Entering the Mainstream

In 2020, Pesta et al. published an article entitled “Racial and Ethnic Group Differences in the Heritability of Intelligence: A Systematic Review and Meta-Analysis” in the journal Intelligence. The authors framed their analysis as an examination of the Scarr-Rowe hypothesis, which holds that the heritability of intelligence varies as a function of socioeconomic status. Pesta et al. concluded that the heritability of intelligence does not differ across racial and ethnic groups in the United States. They claimed their results challenge the Scarr-Rowe hypothesis and support the hereditarian position that mean differences in IQ among racial and ethnic groups are attributable to genetic differences rather than environmental disparities. In this commentary, we outline severe theoretical, methodological, and rhetorical flaws in every step of Pesta et al.’s meta-analysis. The most reliable finding from Pesta et al. is consistent with the Scarr-Rowe hypothesis and directly contradicts a hereditarian understanding of group differences in intelligence. Finally, we suggest that Pesta et al. serves as an example of how racially motivated and poorly executed work can find its way into a mainstream scientific journal, underscoring the importance of robust peer review and rigorous editorial judgment in the open-science era.

More than provocative, less than scientific: A commentary on the editorial decision to publish Cofnas (2020)

This article refers to:Research on group differences in intelligence: A defense of free inquiryEditors’ note

Research on group differences in intelligence: A defense of free inquiry

ABSTRACTIn a very short time, it is likely that we will identify many of the genetic variants underlying individual differences in intelligence. We should be prepared for the possibility that these variants are not distributed identically among all geographic populations, and that this explains some of the phenotypic differences in measured intelligence among groups. However, some philosophers and scientists believe that we should refrain from conducting research that might demonstrate the (partly) genetic origin of group differences in IQ. Many scholars view academic interest in this topic as inherently morally suspect or even racist. The majority of philosophers and social scientists take it for granted that all population differences in intelligence are due to environmental factors. The present paper argues that the widespread practice of ignoring or rejecting research on intelligence differences can have unintended negative consequences. Social policies predicated on environmentalist theories of group differences may fail to achieve their aims. Large swaths of academic work in both the humanities and social sciences assume the truth of environmentalism and are vulnerable to being undermined. We have failed to work through the moral implications of group differences to prepare for the possibility that they will be shown to exist.

Evaluating the relationship between psychometric intelligence and cognitive functions in paediatric multiple sclerosis.

BackgroundProcessing speed is frequently reduced in patients suffering from multiple sclerosis (MS). Reduced processing speed can also lead to impaired working memory capacity (WMC) in adult MS patients. Less is known about the interplay of cognitive deficits in paediatric MS patients.ObjectivesIn the present study, we investigated whether processing speed and WMC are reduced in paediatric MS patients compared with healthy controls and whether reduced processing speed and WMC might explain potential differences in psychometric intelligence between MS patients and healthy controls.MethodsTwenty-one paediatric MS patients and 21 healthy controls completed a reaction time (RT) task, a working memory task, and Cattell’s Culture Fair Test (CFT20-R).ResultsPatients with MS had slower RT and lower intelligence scores than healthy controls. We could find no significant differences for WMC. An analysis of covariance revealed that group differences in intelligence could be partially explained by processing speed differences.ConclusionThe results indicate that processing speed is a good marker for MS-related impaired efficiency and increased error-proneness of the central nervous system in higher-order cognition as required by Cattell’s CFT20-R.

The Intelligence of Biracial Children of U.S. Servicemen in Northeast Asia: Results from Japan

The IQ averages of biracial children have long been of interest to intelligence researchers for clarifying the causes of group differences in intelligence. We carried out a search for IQ test results of biracial children fathered by U.S. servicemen after World War 2 and indigenous Asian women in northeast Asian countries (Japan, Korea, China). We were able to locate a report from Japan from a foster home (n = 28–48 biracial children across tests). Results showed that there was only a minuscule IQ gap (<1 IQ) between children of Black–Japanese and White–Japanese parents. However, interpretation of the results is difficult owing to the very small sample size, the non-representative sample, and unknown patterns of assortative mating. We suggest possible avenues for future research.

Spearman’s Hypothesis Tested Comparing 47 Regions of Japan Using a Sample of 18 Million Children

Many groups differ in their mean intelligence score. Spearman’s hypothesis states that the differences are a function of cognitive complexity. There tend to be large differences on subtests of high cognitive complexity and small differences on subtests of low cognitive complexity. Spearman’s hypothesis has been supported by a large number of studies. Can Spearman’s hypothesis be generalized to regions of a country, where these regions differ in mean intelligence? We utilized data from 86 different cognitive tests from all 47 Japanese prefectures and correlated the g loadings of 86 subtests with standardized differences on the same subtests. Spearman’s hypothesis was clearly supported: the biggest differences between the regions were on the tests that were of the greatest complexity, meaning that Spearman’s hypothesis may be generalizable from groups to regions. In Japan, g loadings offer a better explanation of group differences in intelligence than cultural differences. Future research should explore whether Spearman’s hypothesis is also supported for differences between regions of other countries.

Spearman’s Hypothesis Tested Comparing 47 Regions of Japan Using a Sample of 18 Million Children

Many groups differ in their mean intelligence score. Spearman’s hypothesis states that the differences are a function of cognitive complexity. There tend to be large differences on subtests of high cognitive complexity and small differences on subtests of low cognitive complexity. Spearman’s hypothesis has been supported by a large number of studies. Can Spearman’s hypothesis be generalized to regions of a country, where these regions differ in mean intelligence? We utilized data from 86 different cognitive tests from all 47 Japanese prefectures and correlated the g loadings of 86 subtests with standardized differences on the same subtests. Spearman’s hypothesis was clearly supported: the biggest differences between the regions were on the tests that were of the greatest complexity, meaning that Spearman’s hypothesis may be generalizable from groups to regions. In Japan, g loadings offer a better explanation of group differences in intelligence than cultural differences. Future research should explore whether Spearman’s hypothesis is also supported for differences between regions of other countries.

Religiosity as a predictor of in-group favoritism within and between religious groups

It was hypothesized that religiosity is positively associated with religious in-group favoritism. This hypothesis was tested using the second wave of data from the Midlife in the United States representative survey of middle adulthood. The sample included White participants from four religious groups (Baptists, Catholics, Methodists, and Jews). Consistent with the hypothesis, when analyzing the full sample and within each of the four religious groups, religiosity was predictive of in-group favoritism. However, while differences between religious groups in in-group favoritism emerged, and remained when controlling for the previously found group differences in intelligence and personality, the group differences in in-group favoritism were not mediated by religiosity. For example, while Baptists scored high in both religiosity and in-group favoritism, Jews scored low in religiosity yet high in in-group favoritism. Possible explanations for these findings are discussed, such as genetic similarity among group members.

Science Is Not Always “Self-Correcting”

Some prominent scientists and philosophers have stated openly that moral and political considerations should influence whether we accept or promulgate scientific theories. This widespread view has significantly influenced the development, and public perception, of intelligence research. Theories related to group differences in intelligence are often rejected a priori on explicitly moral grounds. Thus the idea, frequently expressed by commentators on science, that science is “self-correcting”—that hypotheses are simply abandoned when they are undermined by empirical evidence—may not be correct in all contexts. In this paper, documentation spanning from the early 1970s to the present is collected, which reveals the influence of scientists’ moral and political commitments on the study of intelligence. It is suggested that misrepresenting findings in science to achieve desirable social goals will ultimately harm both science and society.

Is the Flynn effect on g?: A meta-analysis

Black/White differences in mean IQ have been clearly shown to strongly correlate with g loadings, so large group differences on subtests of high cognitive complexity and small group differences on subtests of low cognitive complexity. IQ scores have been increasing over the last half century, a phenomenon known as the Flynn effect. Flynn effect gains are predominantly driven by environmental factors. Might these factors also be responsible for group differences in intelligence? The empirical studies on whether the pattern of Flynn effect gains is the same as the pattern of group differences yield conflicting findings. A psychometric meta-analysis on all studies with seven or more subtests reporting correlations between g loadings and standardized score gains was carried out, based on 5 papers, yielding 11 data points (total N=16,663). It yielded a true correlation of −.38, and none of the variance between the studies could be attributed to moderators. It appears that the Flynn effect and group differences have different causes. Suggestions for future research are discussed.

Paired associate learning in children with neurofibromatosis type 1: implications for clinical trials

Studies investigating behavior in mice with a heterozygous null mutation of the NF1 gene (Nf1 (+/-)) have provided critical insights into the molecular and cellular mechanisms underlying cognitive impairments associated with neurofibromatosis type 1 (NF1). Hyperactivation of the Ras-MAPK signaling cascade, which results in increased GABA-mediated inhibition and significantly reduced long-term potentiation, has been proposed as a core mechanism underlying Nf1 (+/-) mice deficits in visuospatial learning and attention. This assertion has been reinforced by preclinical trials that reveal that these impairments can be rescued both at a cognitive and cellular level. We attempted to demonstrate a phenotypic parallel between Nf1 (+/-) mice and children with NF1 using a well-validated measure of visuospatial learning. Children with NF1 (n = 71) and healthy controls (n = 29) were assessed on a computerized paired associate learning task. Interrelationships between visuospatial learning and other cognitive abilities that may influence performance, such as intelligence, attention and visuospatial function, were explored. Children with NF1 displayed significant impairments in visuospatial learning, with reduced initial retention and poorer learning across repeated trials. Importantly, we demonstrated that visuospatial learning was inferior in NF1 even after accounting for group differences in intelligence, sustained attention and visuospatial abilities. We have thus identified impaired visuospatial learning as a core phenotypic feature in children with NF1. These findings imply that hippocampal-based learning networks are dysfunctional in children with NF1 and provide validation for a primary outcome measure for clinical trials aiming to correct aberrant Ras signaling.

The Flynn effect, group differences, and g loadings

Flynn effect gains are predominantly driven by environmental factors. Might these factors also be responsible for group differences in intelligence? Group differences in intelligence have been clearly shown to strongly correlate with g loadings. The empirical studies on whether the pattern of Flynn effect gains is the same as the pattern of group differences yield conflicting findings. We present new evidence on the topic using a number of datasets from the US and the Netherlands. Score gains and g loadings showed a small negative average correlation. The general picture is now that there is a small, negative correlation between g loadings and Flynn effect gains. It appears that the Flynn effect and group differences have different causes.

Executive Function in Pathological Gamblers and Healthy Controls

Executive function (EF) deficits may underlie some of the impulse control problems seen in pathological gambling. Pathological gamblers (PGs, n = 45) and controls (n = 45) were compared on several measures of EF (including measures of response inhibition, working memory, cognitive flexibility and perseveration, planning and decision-making), as well as memory and intelligence tests to examine whether PGs evidence EF dysfunction. Compared with controls, PGs exhibited specific deficits on measures of planning and decision-making. PGs also exhibited relative deficits on a measure of perseveration, but this deficit was no longer significant after controlling for group differences in intelligence. These results suggest that PGs may experience deficits on specific components of EF.

Childhood abuse and verbal intelligence among adults diagnosed with first‐episode schizophrenia

Objective: While many individuals diagnosed with schizophrenia report childhood trauma, little is known about the relationship between childhood abuse and intelligence in this population. Authors hypothesized the abused individuals would show lower verbal IQ. Methods: This preliminary study compared the intelligence profile between 46 adults experiencing first‐episode schizophrenic psychosis with and without a history of childhood physical or sexual abuse. Clinical assessment included the Korean Wechsler Adult Intelligence Scale (K‐WAIS) and an interview assessing history of sexual and repeated physical abuse before age 16. Results: The mean verbal IQ score of patients with a history of childhood abuse (n=21) was significantly lower than that of patients without a history of childhood abuse (n=25; p < .05). However, the mean number of years of education was also significantly lower in those with a history of childhood abuse (p < .001). In fact, an analysis of covariance controlling for education revealed no group differences in intelligence. Conclusions: Childhood trauma may contribute to low verbal intelligence of first‐onset patients diagnosed with schizophrenia by leading to poor educational attainment. Assessment and management of first‐onset patients with childhood abuse need to be tailored for their intellectual level.

Recruitment modeling applied to longitudinal studies of group differences in intelligence

In longitudinal studies data is collected in a series of waves. Each wave after the first suffers from attrition. Therefore it can be difficult to discriminate between changes in sample parameters due to a longitudinal process (e.g. ageing) and changes due to attrition. The problem is particularly vexing if one of the purposes is to compare differences between two or more groups over time, because there may be differential attrition across groups. We refer to this as a recruitment problem, because the sample studied in any wave after the first can be thought of as having been recruited from a preceding wave. We present a mathematical model of the recruitment process. We then apply it to two large longitudinal studies, the British Cohort Survey 1970 and the National Child Development Study (1958), to demonstrate how we can identify effects expected from recruitment alone. As an illustration we show that differential recruitment would predict increasing differences between estimates of men's and women's intelligence as the studied sample ages.

Intellectual Growth during Late Adolescence: Effects of Sex and Race

Group differences in intelligence depend on the age at which the cognitive test is administered. Using data from the NLSY79 in the United States, this study analyzes scores on the Armed Services Vocational Aptitude Battery (ASVAB). The rise in scores on ASVAB subtests, IQ and g is essentially linear from age 15 to 23. The rise is greater for males than females, a difference that is statistically significant (p<.01) for g in the white but not the black group. The rate of age-dependent score increases is considerably greater in Whites than Blacks (p<.001). Possible causes of these age trends are investigated.

Recruitment modeling: An analysis and an application to the study of male–female differences in intelligence

Studies of group differences in intelligence often invite conclusions about groups in general from studies of group differences in selected populations. The same design is used in the study of group differences in other traits as well. Investigators observe samples from two groups (e.g. men and women) in some accessible population, but seek to conclude something about a wider, general population. The most frequent case is probably a study contrasting undergraduate men and women. The investigator will know the method by which people are recruited from the accessible population. However the methods by which the members of each group enter the accessible population from the general population is not under the control of the investigator. Call this the recruitment process. The recruitment process may introduce differences between groups in the accessible population that do not occur in the general population. Continuing the example, the recruitment processes that draw men and women from the college-age population into the population of students may not be the same. Therefore, in order to draw an inference about group differences in the general population from group differences in samples from the accessible population it is necessary to have a model of the recruitment process. We develop such a model, and present data showing that it appears to be valid for the case of recruitment into the population of youth who consider post-secondary education. We illustrate use of the model by analyzing findings from a widely publicized study of differences in intelligence between men and women, and show that the conclusions from that study are modified by consideration of the recruitment process.

Spearman’s Hypothesis: Support from the Wechsler Intelligence Scale for Children, Third Edition

'Spearman's hypothesis' states that Black-White differences in intelligence are largely a function of the demand of a test on the general factor, Spearman's g. The present study investigates Spearman's hypothesis using the standardization sample of the Wechsler Intelligence Scale for Children, Third Edition (WISC-III, 1991). As additional comparison groups, data from two samples of children with sensory impairments were also analyzed. Findings support Spearman's hypothesis as an account of average Black-White differences in subtest performance. Differences on WISC-III in the disabled samples were not significantly related to Spearman's g despite these groups' experience of deprivation. Thus, the deprivation hypothesis is not affirmed, while Spearman's g gains further credibility as an explanation for observed racial differences on IQ-type tests. Key Words: Spearman's hypothesis; WISC-III; Race differences; Intelligence. No practice in psychology has inspired or endured more criticism than testing. Usually, die most strident attacks target the repeated finding that Blacks and Whites differ in varying degrees on tests of intellectual ability (Jensen, 1969, 1980, 1998; Naglieri & Jensen, 1987). These average group differences in America are substantial, of some 15-16 IQ points, and have been observed for more tiian a century, beginning with the widespread use of IQ testing (Ferguson, 1916; Jensen, 1969, 1980; Rushton & Jensen, 2005a; Shuey, 1966; Yerkes, 1921). While researchers generally agree tiiat these differences exist, there has been a massive debate about their origins (Devlin et al., 1997; Kamin, 1974; Mensh & Mensh, 1991; Miele, 1995). The unremitting controversy surrounding the issue of Black-White differences in IQ is fueled by the media and by social researchers who depict research on group differences in intelligence as fundamentally flawed, tacitly racist, and morally reprehensible (Fish, 2002; Gottfredson, 2005; Snyderman and Rothman, 1988; Williams, 1974). In reality, the available empirical research from various disciplines has converged on a portrait of intelligence that is the opposite of conventional wisdom. That is, intelligence is a highly reliable and predictive construct that is subject to developmental growth and decline and is substantially related to elementary cognitive processes, educational achievement, and earnings (Brand, 1996; Carroll, 2005; Gottfredson, 1997, 2002; Herrnstein & Murray, 1994; Legree et al., 1996; Lynn & Vanhanen, 2002; Neisser et al., 1996) and a heritability of around .60 (Jensen, 1998; Loehlin, 2000; Miele, 2002). Controversy about group differences in intellectual performance invariably concerns the general factor of intelligence, g, which was discovered by Charles Spearman in 1904 as part of an experiment to find out whether, as Galton [had] indicated, the abilities commonly taken to be intellectual correlated with each other or with sensory discrimination (Spearman, 1927, p. 322). Spearman obtained teacher evaluations of 36 students from a village school. Students were rated on the usual academic subjects (Latin, English, and Math) as well as Music and Pitch Discrimination. Spearman noticed immediately that all tests correlated positively. These observed linear correlations between the variables prompted Spearman to hypothesize that the variables shared a common source of variance (Spearman, 1927). Additionally, the fact that the correlations between tests differed from one another suggested to Spearman that each test sampled this common source of variance to a varying degree. In the same seminal article, Spearman developed the statistical method of factor analysis for estimating the general factor. He remarked that his variables had different levels of saturation with g, represented by different loadings on the general factor. Spearman devoted the rest of his academic career to explicating g, which he conceptualized as mental energy; he held g was the leading part of intelligence, and is displayed by the ability to handle not merely abstract ideas, but above all symbols (Spearman, 1927; p. …

The Difficulty of Escaping Preconceptions in Writing an Article About the Difficulty of Escaping Preconceptions: Commentary on Hunt and Carlson (2007).

If not for two major unsupported statements, Considerations Relating to the Study of Group Differences in Intelligence would be a superb piece. As it is, Hunt and Carlson (2007, this issue) have written a generally excellent guide to the thorny problem of studying group differences in intelligence. Such an article sensible, well-written, and balanced was sorely needed. This is a field that has been an ideological landmine. We are delighted to see a major work of this high caliber, motivated by science rather than ideology, published in Perspectives on Psychological Science, However, we believe there are two major unsupported statements that mar this otherwise excellent article.