Group differences in mean intelligence for the Dutch and Third World immigrants.

Evidence from eleven samples indicates that the mean IQ of third world immigrants in the Netherlands is lower than the Dutch mean by approximately one standard deviation for Surinamese and Antillians, and by approximately one and a half standard deviations for Turks and Moroccans. Since IQ tests provide the best prediction of success in school and organizations, it could be that the immigrants' lower mean IQ is an important factor in their low status on the Dutch labour market. The IQs of second-generation immigrants are rising.     

Phenylketonuria and its variants: observations on intellectual functioning.

The age at diagnosis, dietary treatment and intelligence quotient (IQ) of 119 patients with phenylketonuria (PKU) and its variants who were under long-term observation were studied. In 27 of the 79 patients with classic PKU the diagnosis had been made and treatment begun late (after 2 months of age). The mean IQ of these 27 patients was 57.6 when they were in their early 20s (although 2 had normal IQs). In contrast, among the 52 patients with classic PKU who were not treated late the mean IQ was 93.6 for the 27 who were still receiving dietary therapy. The mean IQs were 99.3 and 92.7 at ages 5 (when the diet was discontinued) and 15 years respectively for the 12 who had been treated "adequately". It was 76.0 for the 13 who were "over-treated" (malnourished) in the first 6 months of life. Among the patients with atypical PKU, who were treated early, the mean IQs were 110.0 for the 7 who were still receiving dietary therapy and 102.7 for the 12 who were not. The 21 patients with persistent benign hyperphenylalaninemia, who were not treated, had a mean IQ of 104.2. The most important factor in the ultimate IQ of patients with classic PKU is very early diagnosis (by 2 weeks of age) along with immediate initiation of dietary therapy.     

Sex differences on the progressive matrices: some data from Hong Kong

There has been a debate between N. J. Mackintosh and the first author of this paper on whether the sex difference on the Progressive Matrices is zero or, at most, 1-2 IQ points in favour of either sex, as maintained by Mackintosh, or whether from the age of 15 years onwards males obtain higher average scores than females by more than 2 IQ points, as maintained by Lynn. New data relevant to this controversy are presented from Hong Kong consisting of sex differences on the standardization sample of the Advanced Progressive Matrices on 15- to 18-year-olds. The results are that males obtained a higher mean score than females of 1.6 raw score points, equivalent to an advantage of 3.2 or 4.1 IQ points, according to two alternative methods of calculation. The results provide further confirmation that in later adolescence and among adults, males obtain significantly higher mean IQs on the Progressive Matrices than females.     

Intelligence May Moderate the Cognitive Profile of Patients with ASD

BackgroundThe intelligence of individuals with Autism Spectrum Disorder (ASD) varies considerably. The pattern of cognitive deficits associated with ASD may differ depending on intelligence. We aimed to study the absolute and relative severity of cognitive deficits in participants with ASD in relation to IQ.MethodsA total of 274 children (M age = 12.1, 68.6% boys) participated: 30 ASD and 22 controls in the below average Intelligence Quotient (IQ) group (IQ<85), 57 ASD and 54 controls in the average IQ group (85<IQ<115) and 41 ASD and 70 controls in the above average IQ group (IQ>115). Matching for age, sex, Full Scale IQ (FSIQ), Verbal IQ (VIQ), Performance IQ (PIQ) and VIQ-PIQ difference was performed. Speed and accuracy of social cognition, executive functioning, visual pattern recognition and basic processing speed were examined per domain and as a composite score.ResultsThe composite score revealed a trend significant IQ by ASD interaction (significant when excluding the average IQ group). In absolute terms, participants with below average IQs performed poorest (regardless of diagnosis). However, in relative terms, above average intelligent participants with ASD showed the most substantial cognitive problems (particularly for social cognition, visual pattern recognition and verbal working memory) since this group differed significantly from the IQ-matched control group (p < .001), whereas this was not the case for below-average intelligence participants with ASD (p = .57).ConclusionsIn relative terms, cognitive deficits appear somewhat more severe in individuals with ASD and above average IQs compared to the below average IQ patients with ASD. Even though high IQ ASD individuals enjoy a certain protection from their higher IQ, they clearly demonstrate cognitive impairments that may be targeted in clinical assessment and treatment. Conversely, even though in absolute terms ASD patients with below average IQs were clearly more impaired than ASD patients with average to above average IQs, the differences in cognitive functioning between participants with and without ASD on the lower end of the IQ spectrum were less pronounced. Clinically this may imply that cognitive assessment and training of cognitive skills in below average intelligent children with ASD may be a less fruitful endeavour. These findings tentatively suggest that intelligence may act as a moderator in the cognitive presentation of ASD, with qualitatively different cognitive processes affected in patients at the high and low end of the IQ spectrum.     

MRI-Based Intelligence Quotient (IQ) Estimation with Sparse Learning

In this paper, we propose a novel framework for IQ estimation using Magnetic Resonance Imaging (MRI) data. In particular, we devise a new feature selection method based on an extended dirty model for jointly considering both element-wise sparsity and group-wise sparsity. Meanwhile, due to the absence of large dataset with consistent scanning protocols for the IQ estimation, we integrate multiple datasets scanned from different sites with different scanning parameters and protocols. In this way, there is large variability in these different datasets. To address this issue, we design a two-step procedure for 1) first identifying the possible scanning site for each testing subject and 2) then estimating the testing subject’s IQ by using a specific estimator designed for that scanning site. We perform two experiments to test the performance of our method by using the MRI data collected from 164 typically developing children between 6 and 15 years old. In the first experiment, we use a multi-kernel Support Vector Regression (SVR) for estimating IQ values, and obtain an average correlation coefficient of 0.718 and also an average root mean square error of 8.695 between the true IQs and the estimated ones. In the second experiment, we use a single-kernel SVR for IQ estimation, and achieve an average correlation coefficient of 0.684 and an average root mean square error of 9.166. All these results show the effectiveness of using imaging data for IQ prediction, which is rarely done in the field according to our knowledge.     

National IQs predict differences in scholastic achievement in 67 countries

This paper examines the relationship of the national IQs reported by Lynn & Vanhanen (2002, 2006) to national achievement in mathematics and science among 8th graders in 67 countries. The correlation between the two is 0.92 and is interpreted as establishing the validity of the national IQs. The correlation is so high that national IQs and educational achievement appear to be measures of the same construct. National differences in educational achievement are greater than differences in IQ, suggesting an amplifier effect such that national differences in IQs amplify differences in educational achievement. Controlling for national differences in IQ, slight inverse relationships of educational achievement are observed with political freedom, subjective well-being, income inequality, and GDP. However, public expenditure on education (as % of GDP) was not a significant predictor of differences in educational achievement.     

Ethnic and racial differences on the Standard Progressive Matrices in Mexico

Raven's Standard Progressive Matrices test was administered to a representative sample of 920 white, Mestizo and Native Mexican Indian children aged 7-10 years in Mexico. The mean IQs in relation to a British mean of 100 obtained from the 1979 British standardization sample and adjusted for the estimated subsequent increase were: 98.0 for whites, 94.3 for Mestizos and 83.3 for Native Mexican Indians.     

Evaluation of automatic image quality assessment in chest CT – A human cadaver study

PurposeThe evaluation of clinical image quality (IQ) is important to optimize CT protocols and to keep patient doses as low as reasonably achievable. Considering the significant amount of effort needed for human observer studies, automatic IQ tools are a promising alternative. The purpose of this study was to evaluate automatic IQ assessment in chest CT using Thiel embalmed cadavers.MethodsChest CT’s of Thiel embalmed cadavers were acquired at different exposures. Clinical IQ was determined by performing a visual grading analysis. Physical-technical IQ (noise, contrast-to-noise and contrast-detail) was assessed in a Catphan phantom. Soft and sharp reconstructions were made with filtered back projection and two strengths of iterative reconstruction. In addition to the classical IQ metrics, an automatic algorithm was used to calculate image quality scores (IQs). To be able to compare datasets reconstructed with different kernels, the IQs values were normalized.ResultsGood correlations were found between IQs and the measured physical-technical image quality: noise (ρ = −1.00), contrast-to-noise (ρ = 1.00) and contrast-detail (ρ = 0.96). The correlation coefficients between IQs and the observed clinical image quality of soft and sharp reconstructions were 0.88 and 0.93, respectively.ConclusionsThe automatic scoring algorithm is a promising tool for the evaluation of thoracic CT scans in daily clinical practice. It allows monitoring of the image quality of a chest protocol over time, without human intervention. Different reconstruction kernels can be compared after normalization of the IQs.     

Relationship between phenylalanine tolerance and psychological characteristics of phenylketonuric families

The purpose of this study was to find out how genetic and biochemical limitations influence psycho-social performance and to partially test the validity of justification theory. The ability to convert phenylalanine to tyrosine was compared with intellectual and personality characteristics in PKU family members. Each of the tested persons was given an oral dose of phenylalanine, the Shipley-Hartford Intelligence Test, and the Minnesota Multiphasic Personality Inventory (MMPI). Only those persons with reading ability at the sixth grade level or higher were tested. Eighty-six persons were tested: fifteen PKUs, forty-three siblings, and twenty-eight parents. A comparison was made among parents, PKUs, and the siblings. Siblings with the higher 2/3's of P2/T ratios were contrasted with those with the lowest 1/3 of ratios on measures of intelligence and psychopathology. Statistical analyses of the data reflected a trend in support of the justification theory. PKUs had significantly lower intelligence than their sibs and parents. The PKUs' mean IQ was 95 (homozygotes born of heterozygotes), followed by the upper 2/3's sibling mean IQ of 105 (heterozygotes born of nonheterozygote mothers). The lower 1/3 siblings' mean IQ was 107 (nonheterozygotes born from heterozygote mothers), and finally, the parents' mean IQ was 109 (heterozygotes, among them 50% were born from nonheterozygote mothers). The latter three mean IQs are not significantly different from each other. The personality tests revealed a trend toward more abnormality in PKUs than in their heterozygote siblings. The lowest rate of abnormality occurred in the nonheterozygote sibling group; that rate was significantly lower than in all other groups. The parents had the highest absolute rate of personality abnormality, but statistically so compared to the low-ratio siblings.     

Intelligence quotients of pilots in civil aviation with atherosclerotic changes in the brain vessels

Intelligence quotients (IQs) in pilots of civil aviation were studied. A total of 73 healthy pilots (control group) and 70 pilots with atherosclerosis of the brain vessels, including 23 persons with atherosclerotic plaques, were studied. The study of intellectual indices was performed using the classical Eysenck??s tests and their modifications by Gorbov in a computer variant developed by Sobchik. In pilots with atherosclerosis of the brain vessels, a tendency towards an insignificant decrease in the indices of average values of IQ as compared to those of healthy pilots was recorded. The IQs of the examined pilots indicated their occupational fitness. Despite the presence of atherosclerotic plaques in the group of pilots examined by us, the results of numerical (IQ2) and verbal (IQ3) tests were not reduced. The presence of hemodynamically insignificant stable atherosclerotic plaques in pilots examined by us did not lead to a change in the cognitive functions; the intellectual capacities of pilots were preserved, which allowed them to continue flight work.     

Influence of variation in birth weight within normal range and within sibships on IQ at age 7 years: cohort study

ObjectiveTo examine the relation between birth weight and measured intelligence at age 7 years in children within the normal range of birth weight and in siblings.DesignCohort study of siblings of the same sex.Setting12 cities in the United States.Subjects3484 children of 1683 mothers in a birth cohort study during the years 1959 through 1966. The sample was restricted to children born at ⩾37 weeks gestation and with birth weights of 1500-3999 g.ResultsMean IQ increased monotonically with birth weight in both sexes across the range of birth weight in a linear regression analysis of one randomly selected sibling per family (n= 1683) with adjustment for maternal age, race, education, socioeconomic status, and birth order. Within same sex sibling pairs, differences in birth weight were directly associated with differences in IQ in boys (812 pairs, predicted IQ difference per 100 g change in birth weight =0.50, 95% confidence interval 0.28 to 0.71) but not girls (871 pairs, 0.10, −0.09 to 0.30). The effect in boys remained after differences in birth order, maternal smoking, and head circumference were adjusted for and in an analysis restricted to children with birth weight ⩾ 2500 g.ConclusionThe increase in childhood IQ with birth weight continues well into the normal birth weight range. For boys this relation holds within same sex sibships and therefore cannot be explained by confounding from family social environment.

What is already known on this topic

IQ at school age is linked to birth weight among low birthweight babiesSome evidence suggests the association might also apply to children of normal birth weight

What this study adds

IQ at age 7 years is linearly related to birth weight among children of normal birth weightThe relation was not due to confounding by maternal or socioeconomic factorsIQ is also associated with differences in birth weight between boy sibling pairs but not girls     

A genomewide scan for intelligence identifies quantitative trait loci on 2q and 6p

Between 40% and 80% of the variation in human intelligence (IQ) is attributable to genetic factors. Except for many rare mutations resulting in severe cognitive dysfunction, attempts to identify these factors have not been successful. We report a genomewide linkage scan involving 634 sibling pairs designed to identify chromosomal regions that explain variation in IQ. Model-free multipoint linkage analysis revealed evidence of a significant quantitative-trait locus for performance IQ at 2q24.1-31.1 (LOD score 4.42), which overlaps the 2q21-33 region that has repeatedly shown linkage to autism. A second region revealed suggestive linkage for both full-scale and verbal IQs on 6p25.3-22.3 (LOD score 3.20 for full-scale IQ and 2.33 for verbal IQ), overlapping marginally with the 6p22.3-21.31 region implicated in reading disability and dyslexia.     

FADS2 Polymorphisms Modify the Effect of Breastfeeding on Child IQ

Background

Breastfeeding is important for child cognitive development. A study by Caspi et al has suggested that rs174575 within the FADS2 gene moderates this effect so that children homozygous in the minor allele (GG genotype) have similar IQs irrespective of feeding method.

Methods and Principal Findings

In our study of 5934 children aged 8 years, no genetic main effect with IQ was found for rs174575. However, an interaction with this polymorphism was observed such that breastfed GG children performed better than their formula fed counterparts by an additional 5.8 points [1.4, 10.1] (interaction p = 0.0091). Interaction results were attenuated by about 10% after adjustment for 7 factors. This study also investigated rs1535, another FADS2 polymorphism in linkage disequilibrium with rs174575, together with performance and verbal IQ, finding similar results although effect sizes were generally reduced.

Conclusions and Significance

This study did not replicate the findings of Caspi et al. In contrast to their study, GG children exhibited the greatest difference between feeding methods such that breastfed children performed similarly irrespective of child genotype whereas formula fed GG children performed worse than other children on formula milk. Further studies are required to replicate these findings.     

Interaction of nutritional and socioeconomic status as determinants of cognitive development in disadvantaged urban Guatemalan children

The relationship between nutritional status, measured by height for age, and cognition, measured by WISC full-scale IQ, was studied in a longitudinal sample of 459 urban Guatemalan children, aged 4-9 years, from a disadvantage community of the fringe of Guatemala City, examined annually over a 3 year period. Socioeconomic status (SES) was controlled by developing a composite index for each home. The mean IQ differed significantly from the lowest to the highest quartiles of stature, the difference between the two extreme quartiles being approximately 0.3 SD of IQ. There was a significant interaction between SES and stature in their effects on IQ. Whereas nutritional status and SES affected IQ in an additive fashion in the upper three SES quartiles, there was no difference in IQ attributible to stature among children from the most disadvantaged homes. This analysis indicates that the mild-to-moderate protein-energy malnutrition (defined by height for age) that is prevalent among children from disadvantaged environments in developing countries is significantly related to cognitive development. However, in the poorest homes, SES is seen as a more important determinant of cognitive development than stature.     

Environmental lead and children's intelligence: a systematic review of the epidemiological evidence.

OBJECTIVE--To quantify the magnitude of the relation between full scale IQ in children aged 5 or more and their body burden of lead. DESIGN--A systematic review of 26 epidemiological studies since 1979: prospective studies of birth cohorts, cross sectional studies of blood lead, and cross sectional studies of tooth lead. SETTING--General populations of children > or = 5 years. MAIN OUTCOME MEASURES--For each study, the regression coefficient of IQ on lead, after adjustment for confounders when possible, was used to derive the estimated change in IQ for a specific doubling of either blood or tooth lead. RESULTS--The five prospective studies with over 1100 children showed no association of cord blood lead or antenatal maternal blood lead with subsequent IQ. Blood lead at around age 2 had a small and significant inverse association with IQ, somewhat greater than that for mean blood lead over the preschool years. The 14 cross sectional studies of blood lead with 3499 children showed a significant inverse association overall, but showed more variation in their results and their ability to allow for confounders. The seven cross sectional studies of tooth lead with 2095 children were more consistent in finding an inverse association, although the estimated magnitude was somewhat smaller. Overall synthesis of this evidence, including a meta-analysis, indicates that a typical doubling of body lead burden (from 10 to 20 micrograms/dl (0.48 to 0.97 mumol/l) blood lead or from 5 to 10 micrograms/g tooth lead) is associated with a mean deficit in full scale IQ of around 1-2 IQ points. CONCLUSION--While low level lead exposure may cause a small IQ deficit, other explanations need considering: are the published studies representative; is there inadequate allowance for confounders; are there selection biases in recruiting and following children; and do children of lower IQ adopt behaviour which makes them more prone to lead uptake (reverse causality)? Even if moderate increases in body lead burden adversely affect IQ, a threshold below which there is negligible influence cannot currently be determined. Because of these uncertainties, the degree of public health priority that should be devoted to detecting and reducing moderate increases in children''s blood lead, compared with other important social detriments that impede children''s development, needs careful consideration.     

Contribution of Brain Size to IQ and Educational Underperformance in Extremely Preterm Adolescents

Objectives

Extremely preterm (EP) survivors have smaller brains, lower IQ, and worse educational achievement than their term-born peers. The contribution of smaller brain size to the IQ and educational disadvantages of EP is unknown. This study aimed (i) to compare brain volumes from multiple brain tissues and structures between EP-born (<28weeks) and term-born (≥37weeks) control adolescents, (ii) to explore the relationships of brain tissue volumes with IQ and basic educational skills and whether this differed by group, and (iii) to explore how much total brain tissue volume explains the underperformance of EP adolescents compared with controls.

Methods

Longitudinal cohort study of 148 EP and 132 term controls born in Victoria, Australia in 1991-92. At age 18, magnetic resonance imaging-determined brain volumes of multiple tissues and structures were calculated. IQ and educational skills were measured using the Wechsler Abbreviated Scale of Intelligence (WASI) and the Wide Range Achievement Test(WRAT-4), respectively.

Results

Brain volumes were smaller in EP adolescents compared with controls (mean difference [95% confidence interval] of -5.9% [-8.0, -3.7%] for total brain tissue volume). The largest relative differences were noted in the thalamus and hippocampus. The EP group had lower IQs(-11.9 [-15.4, -8.5]), spelling(-8.0 [-11.5, -4.6]), math computation(-10.3 [-13.7, -6.9]) and word reading(-5.6 [-8.8, -2.4]) scores than controls; all p-values<0.001. Volumes of total brain tissue and other brain tissues and structures correlated positively with IQ and educational skills, a relationship that was similar for both the EP and controls. Total brain tissue volume explained between 20-40% of the IQ and educational outcome differences between EP and controls.

Conclusions

EP adolescents had smaller brain volumes, lower IQs and poorer educational performance than controls. Brain volumes of multiple tissues and structures are related to IQ and educational outcomes. Smaller total brain tissue volume is an important contributor to the cognitive and educational underperformance of adolescents born EP.     

The impact of therapy for childhood acute lymphoblastic leukaemia on intelligence quotients; results of the risk-stratified randomized central nervous system treatment trial MRC UKALL XI

Background

The MRC UKALLXI trial tested the efficacy of different central nervous system (CNS) directed therapies in childhood acute lymphoblastic leukaemia (ALL). To evaluate morbidity 555/1826 randomised children underwent prospective psychological evaluations. Full Scale, verbal and performance IQs were measured at 5 months, 3 years and 5 years. Scores were compared in; (1) all patients (n = 555) versus related controls (n = 311), (2) low-risk children (presenting white cell count (WCC) < 50 × 10⁹/l) randomised to intrathecal methotrexate (n = 197) versus intrathecal and high-dose intravenous methotrexate (HDM) (n = 202), and (3) high-risk children (WCC ≥ 50 × 10⁹/l, age ≥ 2 years) randomised to HDM (n = 79) versus cranial irradiation (n = 77).

Results

There were no significant differences in IQ scores between the treatment arms in either low- or high-risk groups. Despite similar scores at baseline, results at 3 and 5 years showed a significant reduction of between 3.6 and 7.3 points in all three IQ scores in all patient groups compared to controls (P < 0.002) with a higher proportion of children with IQs < 80 in the patient groups (13% vs. 5% at 3 years p = 0.003).

Conclusion

Children with ALL are at risk of CNS morbidity, regardless of the mode of CNS-directed therapy. Further work needs to identify individuals at high-risk of adverse CNS outcomes.

Trial registration

ISRCTN: ISRCTN16757172     

Mental status of females with an FMR1 gene full mutation.

The cloning of the FMR1 gene enables molecular diagnosis in patients and in carriers (male and female) of this X-linked mental retardation disorder. Unlike most X-linked disorders, a considerable proportion of the female carriers of a full mutation of the FMR1 gene is affected. In this study, the intelligence quotients (IQs) were ascertained by the Wechsler Adult Intelligence Scale in 33 adult females with a full mutation, with 28 first-degree adult female relatives (mainly sisters) without a full mutation as controls. Seventy-one percent of the females with a full mutation had IQ scores below 85. In paired analysis, no significant correlation could be detected between the IQs of the females with a full mutation and those of their first-degree female relatives, reflecting a dominant effect of the FMR1 gene full mutation in the mental development of females. Considering females with a full mutation only, we observed a significant relation between the proportion of normal FMR1 alleles on the active X chromosome and IQ. We present a model to explain this relationship.     

Differential reproduction: Its relation to IQ test score,education, and occupation

Abstract

The correlations among IQ test score, educational attainment rating, socioeconomic status, total number of children in the family of origin, total number of offspring in completed families, and mean age at birth of live‐born children are examined for a representative sample of the Minnesota white population. Natural selection appears to be favoring an increase in the mean IQ score in the sample, or at least there is no evidence for a decrease. The data show positive marital assortment for IQ score and for educational attainment. Four estimates of the heritability of the phenotype “IQ test score” coincide well with each other. The value of h² estimated from parent‐children regression is 0.631; from a weighted regression of children's scores on the score of the father alone, it is 0.668 and on the score of the mother alone, it is 0.654. The estimate from the intra‐class correlation of full siblings is 0.666.     

Aspirin exposure during the first 20 weeks of gestation and IQ at four years of age

The relationship between maternal aspirin use during the first 20 weeks of pregnancy and the child's IQ at 4 years of age was investigated in 19,226 pregnancies occurring from 1959 to 1966 in the Collaborative Perinatal Project. The mean IQ of children exposed to aspirin was 98.3, which was 2.1 points higher (95% confidence interval = 1.7, 2.6; P less than 0.0001) than that of unexposed children. Adjustment for multiple social, demographic, and other confounders reduced this difference to less than one point in favor of the aspirin exposed group, although statistical significance remained. Total days of exposure was used as an index of dose, and no dose-response relationship between aspirin use and IQ was found. The effect of prenatal aspirin exposure did not vary by infant sex. It is concluded that an adverse effect of aspirin exposure on IQ is unlikely.