Smarty pants
Only in America: Cold Winters Theory, race, IQ and well-being
Bryan Pesta & Peter Poznanski
Intelligence, September–October 2014, Pages 271–274
Abstract:
Cold Winters Theory (CWT; Lynn, 1991) offers a viable explanation for race differences in intelligence. It proposes that IQ gaps exist because of different evolutionary pressures faced by the ancestral humans who left Africa, compared with those who remained. Support for CWT comes by showing correlations between national temperature and IQ. Here we test whether temperature correlates with IQ (and other well-being variables) across the 50 U.S. states. Although human evolution is recent, copious and regional (Wade, 2014), insufficient time has passed for it to have operated on non-native residents of the USA. Instead, CWT must predict no difference — or remain agnostic — on the existence of state-level correlations between temperature and IQ. Nonetheless, even after controlling for race, temperature strongly predicts state: IQ, religiosity, crime, education, health, income and global well-being. Evolution is therefore not necessary for temperature and IQ/well-being to co-vary meaningfully across geographic space.
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Why complex cognitive ability increases with absolute latitude
Federico León & Andrés Burga León
Intelligence, September–October 2014, Pages 291–299
Abstract:
Evolutionary psychologists attribute the superior IQs of light-skinned populations to genetic imprints left by millenary processes promoted by cold. But a novel theory that explains IQ gains observed across recent generations ascribes them to a latitude → UVB radiation → vitamin D3 → parents' sexual hormones → family size → child's intellectual environment → IQ chain of effects. Analyses of 506,347 Peruvian children's math and reading scores from a national census confirmed that complex cognitive ability increases with absolute latitude even under tropical megathermal climates and decreases with high altitude above sea level, birth rate and social development mediate most of the effects, and reading is more strongly influenced than math. The findings weaken the evolutionary cold hypothesis and strengthen the view that contraception has the potential to reduce latitudinal IQ gaps.
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Crimes and the Bell Curve: The Role of People with High, Average, and Low Intelligence
Nik Ahmad Sufian Burhan et al.
Intelligence, November–December 2014, Pages 12–22
Abstract:
The present study examines whether crime rates can be reduced by increasing the IQ of people with high, average, and low IQ. Previous studies have shown that as a determinant of the national level of income per capita growth and technological achievement, the IQ of the intellectual class (those at the 95th percentile of the bell curve distribution of population intelligence) is more important than the IQ of those with average ability at the 50th percentile. Extending these findings, our study incorporates the non-intellectual class (IQ at the 5th percentile) to examine the role of IQ classes in determining crime rates across countries. We conducted hierarchical multiple regression analyses with IQ, seven types of crimes, and nine control variables: urbanization, alcohol consumption, unemployment rate, young to old population ratio, income inequality, education attainment, drug consumption, police rate, and income per capita. Regardless of types of crimes, we found evidence that raising IQ will lessen crime rates, with raises in the 95th percentile group having the most number of significant impacts, followed by the 50th and then the 5th percentile groups. Furthermore, none of the nine control factors was stronger than the 95th percentile group in predicting crime rates. We conclude that the intellectual class influences rates of more types of crime than the non-intellectual class does. The intellectual class has the highest authority in determining law enforcement and development policies. Therefore, increasing the IQ of politicians and leaders from this class than other social classes will have a more significant influence in reducing crime rates, through enhanced functionality and quality of institutions across countries.
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Janet Held, Thomas Carretta & Michael Rumsey
Military Psychology, May 2014, Pages 199-220
Abstract:
With the exception of Assembling Objects (AO), a spatial ability test used only by the Navy in enlisted occupational classification, the Armed Services Vocational Aptitude Battery (ASVAB) is academic and knowledge-based, somewhat limiting its utility for occupational classification. This article presents the case for integrating the AO test into military classification composites and for expanding the breadth of ASVAB content by including a former ASVAB speed/accuracy test, Coding Speed (CS). Empirical evidence is presented that shows AO and CS (a) increment the validity of the ASVAB in predicting training grades for a broad array of occupations, (b) reduce adverse impact defined as test score barriers for women and minorities, and (c) improve classification in terms of matching recruits to occupations. Some cognitive theory is presented to support AO and CS, as well as nonverbal reasoning and working memory tests for inclusion in or adjuncts to the ASVAB.
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Hannah Peach, Jordan Lyerly & Charlie Reeve
Personality and Individual Differences, December 2014, Pages 56–59
Abstract:
The purpose of this study is to replicate recent findings demonstrating that the dysgenic fertility trend is a Jensen effect. Data were drawn from Project TALENT. Present analyses included data from a total sample of 79,734 participants with complete data regarding number of biological children at the 11 year follow up, and analyses were further split by sex and race to examine possible differential trends among subgroups. Correlated vectors analyses revealed strong Jensen effects such that subtests with higher g-saturation were associated with larger dysgenic fertility gradients. This effect was evident in the total sample, and within all race/gender subgroups except for Asian males. Such findings yield further confirmation that g is in fact the principal factor by which the dysgenic fertility gradient operates.
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General intelligence, disease heritability, and health: A preliminary test
Satoshi Kanazawa
Personality and Individual Differences, December 2014, Pages 83–85
Abstract:
Cognitive epidemiology shows that more intelligent individuals stay healthier and live longer, but it is not known why. The system integrity theory predicts that more intelligent individuals are more protected from diseases that are more heritable, while the evolutionary novelty theory predicts that they are more protected from diseases that are less heritable. The paper proposes a new method of testing the competing hypotheses. An analysis of two large-scale population data sets from Sweden (n = 1 million for individual data and n = 9.6 million for heritability data) shows that intelligence is more important for health when the cancer heritability is low, supporting the evolutionary novelty theory. While the present results are merely suggestive, not conclusive, the proposed method can be extended to include other diseases and causes of death.
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Cornelius Rietveld et al.
Proceedings of the National Academy of Sciences, 23 September 2014, Pages 13790–13794
Abstract:
We identify common genetic variants associated with cognitive performance using a two-stage approach, which we call the proxy-phenotype method. First, we conduct a genome-wide association study of educational attainment in a large sample (n = 106,736), which produces a set of 69 education-associated SNPs. Second, using independent samples (n = 24,189), we measure the association of these education-associated SNPs with cognitive performance. Three SNPs (rs1487441, rs7923609, and rs2721173) are significantly associated with cognitive performance after correction for multiple hypothesis testing. In an independent sample of older Americans (n = 8,652), we also show that a polygenic score derived from the education-associated SNPs is associated with memory and absence of dementia. Convergent evidence from a set of bioinformatics analyses implicates four specific genes (KNCMA1, NRXN1, POU2F3, and SCRT). All of these genes are associated with a particular neurotransmitter pathway involved in synaptic plasticity, the main cellular mechanism for learning and memory.
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Metabolic costs and evolutionary implications of human brain development
Christopher Kuzawa et al.
Proceedings of the National Academy of Sciences, 9 September 2014, Pages 13010–13015
Abstract:
The high energetic costs of human brain development have been hypothesized to explain distinctive human traits, including exceptionally slow and protracted preadult growth. Although widely assumed to constrain life-history evolution, the metabolic requirements of the growing human brain are unknown. We combined previously collected PET and MRI data to calculate the human brain’s glucose use from birth to adulthood, which we compare with body growth rate. We evaluate the strength of brain–body metabolic trade-offs using the ratios of brain glucose uptake to the body’s resting metabolic rate (RMR) and daily energy requirements (DER) expressed in glucose-gram equivalents (glucosermr% and glucoseder%). We find that glucosermr% and glucoseder% do not peak at birth (52.5% and 59.8% of RMR, or 35.4% and 38.7% of DER, for males and females, respectively), when relative brain size is largest, but rather in childhood (66.3% and 65.0% of RMR and 43.3% and 43.8% of DER). Body-weight growth (dw/dt) and both glucosermr% and glucoseder% are strongly, inversely related: soon after birth, increases in brain glucose demand are accompanied by proportionate decreases in dw/dt. Ages of peak brain glucose demand and lowest dw/dt co-occur and subsequent developmental declines in brain metabolism are matched by proportionate increases in dw/dt until puberty. The finding that human brain glucose demands peak during childhood, and evidence that brain metabolism and body growth rate covary inversely across development, support the hypothesis that the high costs of human brain development require compensatory slowing of body growth rate.