The Relationship Between Blood Lead,Bone Lead and Child Intelligence

We report associations between serial measures of blood lead and intelligence in children age 10–12 years, half heavily exposed to lead from the prenatal period onward, and half relatively unexposed. For a subsample, we examine bone lead-IQ associations, comparing them with blood lead associations. Both blood and bone lead levels were associated with intelligence decrements, small relative to the contribution of social factors. For each doubling of Tib-Pb, Full Scale, Performance, and Verbal IQ decreased by an estimated 5.5, 6.2, and 4.1 points, respectively. Bone lead-IQ associations were stronger than those for blood lead, which nonetheless provide robust analogues. Current BPb, easy to obtain, provides a useful means for assessing Pb exposure/IQ associations.     

Low-level lead exposure, executive functioning, and learning in early childhood.

The current paper presents evidence relating low-level lead exposure to impaired executive functioning in young children. Using the Shape School task, we assessed focused attention, attention switching, working memory, and the ability to inhibit automatic responses in a cohort of 170 children. Participants performed the Shape School task at both 48 and 54 months of age; the mean blood lead level was 6.49 microg/dl at 48 months. After controlling for a wide range of sociodemographic, prenatal, and perinatal variables, blood lead level was negatively associated with children's focused attention while performing the tasks, efficiency at naming colors, and inhibition of automatic responding. In addition, children with higher blood lead levels completed fewer phases of the task and knew fewer color and shape names. There was no association between blood lead and performance on the most difficult tasks, those requiring attention switching or the combination of inhibition and switching. Children's IQ scores were strongly associated with blood lead and Shape School performance, and when entered as a covariate, only color knowledge and the number of tasks completed remained significant. Results provide only weak support for impaired executive functioning, but the deficits in color knowledge may indicate a primary sensory deficit or difficulty with forming conditional associations, both implicating disruptions in dopamine system function.     

Cross-national social ecology of intelligence and suicide prevalence: integration, refinement, and update of studies

This study integrates, refines, and updates previous findings pertaining to positive ecologic (population-level) associations between intelligence and suicide prevalence across nations by using corrected and revised national IQ estimates and, further, a quality-of-human-conditions index, both recently published by Lynn and Vanhanen. Across a global 85-nation sample of sex-specific total suicide rates and a Eurasian 48-nation sample of sex-specific elderly suicide rates, these were positively associated with updated national IQ estimates. The associations were stronger for the general population than for elderly persons, independent of the quality of human conditions, and notedly stronger in exponential fitting of suicide rates with national IQ than in linear fitting, thereby indicating that shifts or differences in national IQ correspond to proportional, not absolute, changes in suicide rates. Implications of these findings and the question of generalizability of such associations to the individual level are discussed.     

How intelligence and education contribute to substance use: Hints from the Minnesota Twin family study

In old and even middle age, there are associations between physical health and both intelligence and education. This may occur because intelligence and/or education exert effects on lifestyle choices that, in turn, affect later health. Substance use is one aspect of lifestyle choice in young adulthood that could play such a role. The effects of intelligence and/or education on substance use could be direct and environmental, or indirect due to the presence of confounding genetic and shared family influences. We used the Minnesota Twin Family Study to distinguish these effects in males and females at age 24. In contrast to prevailing expectations, there were moderately negative direct nonshared environmental effects of both IQ and education on both smoking and drinking in both males and females. That is, controlling for family background effects in the form of both genetic and shared environmental influences, both higher IQ and greater education were associated with greater alcohol and nicotine use. These effects were accounted for by alcohol and nicotine use at age 17. Our results suggest that genetic and family-culture variables confound the associations between intelligence and education and substance use in young adults, rendering them indirect. Further research is needed to understand the roles of IQ and education in alcohol and nicotine use and their relative impacts on physical health throughout the lifespan.     

The Relationship of Trait EI with Personality,IQ and Sex in a UK Sample of Employees

The relationships among trait emotional intelligence (EI), personality, IQ and sex were investigated in a sample of 585 employees (478 males, 107 females). Participants completed the Watson–Glaser Critical Thinking Appraisal, the Bar‐On Quotient Inventory (EQ‐i) and the Neuroticism–Extraversion–Openness Personality Inventory Revised. Bivariate correlations revealed significant associations between overall EQ‐i and Neuroticism (negative), Agreeableness, Extraversion, Openness and Conscientiousness (all positive). While there were no significant associations between overall EQ‐i and sex or IQ, significant correlations were observed when EI components were considered. Male participants scored significantly higher on Adaptability and females scored significantly higher on the Interpersonal facet. Moreover, IQ correlated with the Interpersonal composite in the male' sample. Results are discussed in the context of trait EI structure and its implications for interpretation of sex and IQ effects.     

Intelligence and spatiotemporal patterns of event-related desynchronization (ERD)

Recently, several studies have reported negative associations between brain activity under cognitive load and psychometric intelligence. The position emission tomography (PET) used in these studies allows a high spatial resolution, but it does not permit an assessment of the temporal course of cerebral activation. Therefore, this study examined the relationship between psychometric intelligence (determined by Raven's Advanced Progressive Matrices) and spatiotemporal patterns of cortical activation. Seventeen university students performed an elementary cognitive task, the Sentence Verification Test (SVT), during which the electroencephalogram (EEG) was recorded. In the EEG, the event-related desynchronization (ERD) was quantified, which can be interpreted as a correlate of cortical activation. Lower IQ participants displayed a comparatively unspecific cortical activation increasing with time, whereas higher IQ participants were characterized by a temporal development of activation in those cortical regions that are required for task performance, resulting in less overall activation as compared to the lower IQ participants. These findings support the hypothesis of a more efficient use of the brain in higher IQ individuals.     

Genetic and environmental transactions underlying educational attainment

This report used a population-representative longitudinal twin study with two birth cohorts to explore the association between intelligence and education by understanding how genetic and environmental influences on intelligence moderate genetic and environmental influences on school grades and educational attainment. Nonshared environmental influences on grades were strong when IQ was low, but decreased across the range of IQ. Shared environmental influences common to age 24 educational attainment and age 17 IQ were strong when IQ was low, but genetic influences common to IQ and education were strong when IQ was high. These results suggest that the causal mechanisms linking educational variables with intelligence differ for people with different levels of intelligence.     

Models of Educational Career With and Without IQ Measurements

Path models of educational careers do not usually contain information about phenotypical intelligence levels. This may lead to an overestimation of direct environmental effects such as the educational level of the parents on the education attained by the children. This phenomenon was investigated on the basis of data describing educational level, occupational status, and intelligence measurements of 2,847 father-son pairs. The IQ was determined during testing for military service by means of a shortened version of Raven's Progressive Matrices Test. The results were twofold. When the son's IQ was included in the model describing his educational career, environmental effects due to the influence of the father were reduced. Adding the father's IQ to the model, however, did not affect the path coefficients of the variables that were predicted to be relevant for the son's education.     

Dietary patterns and intelligence in early and middle childhood

The association between intelligence and diet at 3.5 and 7 years was examined in 591 children of European descent. Approximately half of the children were born small-for-gestational age (birth weight ≤ 10th percentile). The relationship between IQ and diet (measured by food frequency) was investigated using multiple regression analyses. Eating margarine at least daily was associated with significantly lower IQ scores at 3.5 years in the total sample and at 7 years in SGA children. For all children, eating the recommended daily number of breads and cereals was associated with significantly higher IQ scores at 3.5 years, and those who ate fish at least weekly had significantly higher IQ scores at 7 years than those who did not. The consumption of fish, breads and cereals commeasurable with nutritional guidelines may be beneficial to children's cognitive development. In contrast, consuming margarine daily was associated with poorer cognitive functioning. Further research is needed to identify the nutrients that may underlie this association.     

Exponential fitting of suicide rate and national intelligence estimates

Positive ecological (group-level) associations of Lynn and Vanhanen's 2002 national intelligence (IQ) estimates with the suicide rates of men and women across 85 countries and with the suicide rates of the male, female, and total elderly population across 48 Eurasian countries reported recently is extended by the finding that this ecological association was notedly better accounted for by exponential fitting than by linear fitting. This evidence implies that the effect of a shift in the national IQ on the suicide rate is proportional, not absolute. As a rule of thumb, a 5-point shift in national IQ roughly corresponds to a 50% change in the national suicide rate.     

Is IQ in Childhood Associated with Suicidal Thoughts and Attempts? Findings from The Mater University Study of Pregnancy and Its Outcomes

This study explores associations of IQ at age 14 with adult symptoms of suicidal thoughts and attempts at age 21. Analysis was based on the Mater University Study of Pregnancy and its outcomes, an Australian prospective birth cohort study started in Brisbane Australia in 1981. We assessed associations with suicide thoughts, plans, and attempts. We used two measures of IQ: the Raven's Standard Progressive Matrices and the Wide Range Achievement Test. In multivariable analyses, there was an inverse association between Raven's IQ and suicide thoughts, plans, and attempts, but no strong evidence of an association between the WRAT3 and the three suicidal items. Specific aspects of intelligence may be associated with suicidal thoughts, plans, and attempts.     

Individual Differences and Beliefs Concerning Preference for University Assessment Methods

This paper explores the relationship between personality, IQ, gender, beliefs about intelligence, and preference for assessment methods at university in 3 separate studies. Study 1 ( N = 367) examined attitudes toward examinations (ATE) and attitudes toward continuous assessment (ATCA) using specific assignments with regard to subjectively assessed intelligence (SAI), entity and incremental beliefs about intelligence (BAI), just-world beliefs, and gender. Studies 2 ( N = 120) and 3 ( N = 93) found significant and negative associations between neuroticism and preference for both essay-type and oral exams. IQ was positively and significantly related to preference for multiple-choice exams. Study 3 tested the relationship of preference for assessment methods with academic performance. Results indicated that preferences are associated with individual differences, rather than academic performance. Findings are discussed in terms of the advantages and disadvantages of introducing alternative methods of student assessment at the university level.     

Implicit theories of intelligence and IQ test performance in adolescents with Generalized Anxiety Disorder

During the past decade, several studies have reported positive effects of cognitive-behavioral therapy (CBT) in the treatment of children and adolescents with mental disorders. One of the most important CBT interventions is to teach children and adolescents to challenge negative thoughts that lead to maladjusted behaviors. Based on the implicit theories of intelligence framework, the main purpose of this study was to test whether an incremental theory manipulation could be used to affect IQ test performance in adolescents with Generalized Anxiety Disorder (GAD). Results showed that patients demonstrated enhanced IQ performance and experienced less state anxiety when they were exposed to an incremental theory of intelligence manipulation. Our findings suggest that incremental theory manipulation provides a useful cognitive strategy for addressing school-related anxiety in adolescents with mental disorders such as GAD.     

Typical intellectual engagement and cognition in the ninth decade of life: The Lothian Birth Cohort 1921

Investment traits-the tendency to seek out and engage in cognitive activity-might affect intellectual growth across the life span, specifically the development from fluid to crystallized intelligence. Here we explore how childhood IQ at age 11 years, IQ at age 79, and the investment trait Typical Intellectual Engagement (TIE) at age 81 affect the mean level and change in verbal fluency scores, used as an indicator of crystallized intelligence, across the ages 79, 83, and 87 in the Lothian Birth Cohort 1921 (maximum N = 569; Deary, Whiteman, Starr, Whalley, & Fox, 2004). A first latent growth model showed significant variance in the mean level of verbal fluency and significant decline in verbal fluency from age 79 to age 87. The rate of change was invariant across study participants in the Lothian Birth Cohort 1921. A second model found that IQ at age 11 significantly predicted IQ at age 79 (β = .66; p < .001), which in turn predicted verbal fluency and TIE in the ninth decade of life with standardized path parameters of .46 and .15 (p < .001), respectively. TIE had a significant association with verbal fluency (β = .14, p = .002); together, IQ at age 11 and 79 and TIE accounted for 25.5% of the variance in verbal fluency. A final model identified the TIE subfactor of intellectual curiosity as a significant mediator of the effect of IQ on verbal fluency; the TIE subfactors abstract thinking, reading, and problem solving showed no significant associations. In summary, TIE-in particular, intellectual curiosity-significantly mediated the effects of IQ on crystallized intelligence in old age. Because there was no significant between-subjects variance in verbal fluency trajectories in the current study, neither TIE nor IQ were associated with individual differences in cognitive decline. (PsycINFO Database Record (c) 2012 APA, all rights reserved).     

Overview of the Flynn effect

Following WW2, various researchers found and reported secular gains in IQ, but it was not until additional reports appeared in the 1980s that researchers began to look for the cause or causes. It was quickly apparent that the gains were not limited to any group or nation, but the manifestation of the gains was different depending on time and place. For every discovery, there was a different or opposite result in a different data set. Gains have been large, small, variable, and even negative. Some researchers have found that the gains were on g, while more have found no g loading. Abstract test formats, such as the Raven have often shown the greatest gains, but gains have also appeared in tests of crystallized intelligence. Some data has shown greater gains for the lower half of the intelligence distribution, while others have shown greater gains in the top half, and others have shown equal gains at all levels. Hypotheses for the causes have included environmental factors, genetic effects, reduced fertility, and methodological dependence. Two models are discussed.     

Can SMART Training Really Increase Intelligence? A Replication Study

A burgeoning research stream supports the efficacy of a novel behavior-analytic intervention, known as SMART training, in raising general intelligence by training a set of crucial cognitive skills, referred to as relational skills. A sample of Irish secondary school students (n?=?26) was divided into two IQ matched groups, with the experimental group receiving 12 weeks of SMART training delivered in bi-weekly 45-min sessions. WASI IQ assessments were administered at baseline and follow-up to all participants by blind testers. For each of the three WASI IQ indices and the four IQ subtests, significant follow-up rises were found for the experimental group only. Analyses of variance indicated a significant effect of training on Verbal IQ, Matrix Reasoning and Vocabulary scores. Results lend further support for the efficacy of the SMART training program in enhancing intellectual skills.     

Flexibility and Originality in Children's Divergent Thinking

Previous research on the ideational process indicates that original ideas increase in frequency as an examinee works through an open-ended task. In the present investigation, ideational flexibility was evaluated to determine if ideas also become more varied and diverse. Additionally, the relationship of intelligence (IQ) with order effects of both originality and flexibility was investigated. Tests of verbal and figural divergent thinking were administered to 80 intermediate school children. The midpoint of each individual's ideational set was found, and the flexibility and originality scores of each half of the set were compared. Results indicated that flexibility and originality scores were higher in the second half than the first half of the ideational set, but there were significant differences between high- and low-originality subjects and differences between the verbal and the figural tests. The order effect was unrelated to the IQ scores of the subjects. Suggestions are made to integrate ideational flexibility into existing theories of divergent ideation.     

The association of childhood intelligence with mortality risk from adolescence to middle age: Findings from the Aberdeen Children of the 1950s cohort study

There is growing evidence that childhood IQ is inversely associated with mortality in later life. However, the specificity of this association in terms of causes of death, whether it is continuous over the whole range of IQ scores and whether it is the same according to age and sex is not clear. In a large cohort (N = 11,603) of a complete population of children born in one city in the UK in the early 1950s, IQ measured at age 7 years (using a routinely administered picture test) was found to be inversely associated with mortality between the ages of 15 and 57 years. For every 1 SD increase in IQ at 7, the all cause mortality hazard ratio was 0.79 (95% CI 0.73, 0.85). On adjustment for a range of perinatal factors, father's social class at birth, number of sibs in the household and childhood height and weight, this was attenuated slightly to 0.81 (0.74, 0.88). Almost identical associations of IQ with mortality were seen for men and women as well as at younger (15–39) and older (40+) ages. These associations were across the entire IQ range, although some of the high mortality in the lowest category of IQ (< 70) was accounted for by causes associated with congenital disorders. Overall, external causes of death showed the strongest association, with weaker associations being seen for cancer. Further work is required to understand the mechanisms whereby childhood IQ has such a robust association with mortality in later life.     

Reverse causation in activity-cognitive ability associations: the Lothian Birth Cohort 1936

Active lifestyles might protect cognitive abilities; however, studies rarely consider the reverse causal direction. Activity-cognition associations might reflect stable intelligence differences rather than a protective effect of activity. The Lothian Birth Cohort 1936 (n = 1091) completed cognitive tests aged 70, having taken an intelligence test aged 11. Activity (assessed by participation in 15 activities that produced a socio-intellectual activity factor, and by physical activity) was positively associated with cognition (r = .08 to .32, p ≤ .05). When age-11 IQ and adult social class were controlled, only physical activity remained significantly associated with general cognitive ability and processing speed.