Regional Differences in Intelligence in 22 Countries and their Economic, Social and Demographic Correlates: A Review

Why are there differences across German states in student achievement and cognitive ability?

Background

For more than twenty years, large and generally stable differences in academic achievement and cognitive ability have been reported within Germany. In such studies, the southern regions lead in the west and east, while city-states lag behind. Expressed in school learning time, the students in Bavaria are 14 months ahead of the students in Bremen. It is striking that there are no or only marginally received studies on causes and consequences.

Purpose

This study attempts to explore the causes and consequences of the differences within Germany and what can be learned in general about their development.

Materials and methods

We use data from student assessment and other studies (e.g., PISA, IQB) and apply correlational and path analyses, controlled for various background factors.

Results

There are no stable correlations with evolution (genes), educational level of society (adult school years) and wealth (GDP per capita). However, there are high correlations, robust across indicators, with "burgher-conservative" education policies, e.g., central exit examinations, early tracking, grades at a young age (around r ≈ .65); with measures of students' quantity of education (hours of instruction, no teacher shortage; r ≈ .40); with measures of tertiary educational quality and appreciation of education (university quality, short duration of studies, professors' salaries; r ≈ .50); with student native/immigrant ratio (r ≈ .50); with middle-class burgher lifestyle (less private debt, less welfare dependency and less crime; r ≈ .60); and with burgher-conservative-right politics (share of votes for CDU/CSU and non-left parties, non-left state governments; r ≈ .80). Longitudinal analyses over four decades reveal interaction effects, i.e., more burgher policies statistically lead to more cognitively competent students (β ≈ .45) and more cognitively competent populations vote for burgher parties (β ≈ .30).

Conclusions

The results, which support the efficacy a bourgeois-conservative education policy and of lower immigration rates, are delicate for the practice of student achievement research and for the political milieu that dominates the social sciences.

Differences in rates of impairment in adults who use methamphetamine using two sets of demographically corrected norms

Neuropsychologists can expect to meet with increasing rates of patients who use methamphetamine (MA), as MA use is on the rise, often comorbid with other substance use disorders, and frequently accompanied by changes in cognitive functioning. To detect impairment, neuropsychologists must apply the appropriate normative data according to important demographic factors such as age, sex, and education. This study involved 241 adults with and without MA dependence who were administered the Neuropsychological Assessment Battery. Given the high rates of polysubstance use among adults who use MA, we included adults with mono-dependence and poly-dependence on MA and at least one other substance. We compared the rates of adults with and without previous MA dependence classified as impaired on neurocognitive testing when using norms corrected for age, education, and sex versus norms corrected only for age. Norms corrected for age, education, and sex resulted in less frequent identification of impairment compared to norms corrected only for age, but both sets of norms appeared sufficient and similar enough to warrant their use with this population. It may be appropriate to explore the possible implications of discrepancies between education-corrected and non-education corrected sets of scores when assessing impairment in individuals who use MA.

Association Between Sleep Duration and Intelligence Quotient in 6-Year-Old Children

BACKGROUND

Sufficient sleep during childhood is important for cognitive functions such as learning and successful school performance. This study aimed to investigate the effects of sleep duration on the intelligence quotient (IQ) of 6-year-old children and aimed to analyze whether these effects differed by sex.

METHODS

The IQ of 538 6-year-old Korean participants from the cohort study, "The Environment and Development of Children," was measured during follow-up using the Korean Educational Developmental Institute's Wechsler Intelligence Scale for Children. The total, verbal, and performance IQ scores were evaluated. The relationship between sleep duration and IQ scores after adjusting for maternal age, maternal educational level, maternal occupation, maternal IQ, exposure to secondhand smoking, gestational age, and monthly age and birth season was also assessed.

RESULTS

Longer sleep duration was significantly associated with improved verbal IQ measures (β 0.55; p value 0.030). After stratifying participants by sex, a significant association was observed between sleep duration and total, verbal, and performance IQ scores in boys (total IQ 2.49, p value 0.012; verbal IQ 0.75, p value: 0.037; performance IQ 0.73, p value 0.048), but not in girls.

CONCLUSIONS

The results indicated that only boys show a significant association between IQ scores and sleep duration. These findings support the hypothesis that sleep duration is associated with IQ, in a sex dependent manner. Future studies are needed for a thorough evaluation of the connection between sleep duration and health outcome in young children.

Sex chromosome aneuploidy alters the relationship between neuroanatomy and cognition

Sex chromosome aneuploidy (SCA) increases the risk for cognitive deficits, and confers changes in regional cortical thickness (CT) and surface area (SA). Neuroanatomical correlates of inter-individual variation in cognitive ability have been described in health, but are not well-characterized in SCA. Here, we modeled relationships between general cognitive ability (estimated using full-scale IQ [FSIQ] from Wechsler scales) and regional estimates of SA and CT (from structural MRI scans) in both aneuploid (28 XXX, 55 XXY, 22 XYY, 19 XXYY) and typically-developing euploid (79 XX, 85 XY) individuals. Results indicated widespread decoupling of normative anatomical-cognitive relationships in SCA: we found five regions where SCA significantly altered SA-FSIQ relationships, and five regions where SCA significantly altered CT-FSIQ relationships. The majority of areas were characterized by the presence of positive anatomy-IQ relationships in health, but no or slightly negative anatomy-IQ relationships in SCA. Disrupted anatomical-cognitive relationships generalized from the full cohort to karyotypically defined subcohorts (i.e., XX-XXX; XY-XYY; XY-XXY), demonstrating continuity across multiple supernumerary SCA conditions. As the first direct evidence of altered regional neuroanatomical-cognitive relationships in supernumerary SCA, our findings shed light on potential genetic and structural correlates of the cognitive phenotype in SCA, and may have implications for other neurogenetic disorders.

Contributing Towards a Cultural Neuropsychology Assessment Decision-Making Framework: Comparison of WAIS-IV Norms from Colombia, Chile, Mexico, Spain, United States, and Canada

OBJECTIVE

Test and normative data selection in cross-cultural neuropsychology remain a complex issue. Despite growing awareness, more studies and instruments are needed to adequately address the impact of cultural factors, such as quantity and quality of education. In this study, we examine the interpretive effects of applying six relevant WAIS-IV norms to a Colombian sample.

METHOD

A sample of 305 highly educated Colombian corporate executives completed the WAIS-IV. Data were scored using norms from Colombia, Chile, Mexico, Spain, United States, and Canada and scores were compared using ANOVA. Additionally, a comparative sociodemographic framework was established to contextualize our sample to the standardization samples and populations of the six countries.

RESULTS

Colombian and Chilean norms yielded systematically similar FSIQ/Index scores (mean range = 117-121), while incrementally lower scores were found with norms from Mexico (-3-9 points), Spain (-3-11 points), USA (-8-13 points), and Canada (-11-18 points). Verbal scores differed, with highest scores obtained with Mexican and Spanish norms. Working memory and processing speed scores had the lowest score agreement across norms.

CONCLUSIONS

Although the Chilean norms are more frequently used in Colombia, the recently developed Colombian norms appear optimal for our sample; the scores do not have meaningful differences with those obtained with Chilean norms and offer local population representation fidelity. Mexican, Spanish, US, and Canadian norms underestimated WAIS-IV scores and distorted the sample's score distribution. Finally, verbal scores highlight potential education representation within Spanish and Mexican norms, while working memory and processing speed scores suggest cultural nuances likely captured within different norms.