Temperature, skin color, per capita income, and IQ: An international perspective

Abstract

The impetus for our study was the contention of both Lynn Race differences in intelligence: A global perspective. Mankind Quarterly, 31, 255-296] and Rushton (Rushton . Race, evolution and behavior: A life history perspective. New Brunswick, NJ: Transaction; Rushton, J. P. (1997). Race, intelligence, and the brain: The errors and omissions of the revised edition of S.J. Gould's the mismeasurement of man. Personality and Individual Differences, 23, 169-180;Rushton, J. P. (2000). Race, evolution, and behavior. A life history perspective (3rd edition). Port Huron: Charles Darwin Research Institute] that persons in colder climates tend to have higher IQs than persons in warmer climates. We correlated mean IQ of 129 countries with per capita income, skin color, and winter and summer temperatures, conceptualizing skin color as a multigenerational reflection of climate. The highest correlations were À 0.92 (rho = À 0.91) for skin color, À0.76 (rho = À0.76) for mean high winter temperature, À0.66 (rho = À 0.68) for mean low winter temperature, and 0.63 (rho = 0.74) for real gross domestic product per capita. The correlations with population of country controlled for are almost identical. Our findings provide strong support for the observation of Lynn and of Rushton that persons in colder climates tend to have higher IQs. These findings could also be viewed as congruent with, although not providing unequivocal evidence for, the contention that higher intelligence evolves in colder climates. The finding of higher IQ in Eurasians than Africans could also be viewed as congruent with the position of Diamond (1997) that knowledge and resources are transmitted more readily on the Eurasian west-east axis. D 2005 Elsevier Inc. All rights reserved.Both Rushton ( , 1997Rushton ( , 2000 and have pointed out that ethnic groups in colder climates score higher on intelligence tests than ethnic groups in warmer climates. They contend that greater intelligence is needed to adapt to a colder climate so that, over many generations, the more intelligent members of a population are more likely to survive and reproduce. Their temperature and IQ analyses have been descriptive rather than quantitative, however. In the present quantitative study, we predicted a negative correlation between IQ and temperature. We hypothesized that correlations would be higher for mean winter temperatures (January in the Northern Hemisphere and July in the Southern Hemisphere) than for mean summer temperatures. Skin color was conceptualized as a variable closely related to temperature. It is viewed by the present authors as a multigenerational reflection of the climates one's ancestors have lived in for thousands of years. Another reason to predict correlations of IQ with temperature and skin color is the product-moment correlation reported by Beals, Smith, and Dodd (1984) from every continent and representing 122 ethnically distinguishable populations. Jensen (1998) reasoned that natural selection would favor a smaller head with a less spherical shape...

Intelligence and gender (in)equality: Empirical evidence from developing countries

“…In the same vein, similar studies suggest that ultraviolet exposure has a detrimental association with cognitive abilities (Silber et al, 1992;Templer & Arikawa, 2006 2 ). For instance, a recent article by Leon (2015) documents that UV exposure explains the geographic differences in the cognitive abilities in the USA.…”

Statistical inference and spatial patterns in correlates of IQ

“…Cross-national research in mean IQ is a relatively new field but has already produced a number of studies which have sought predictors of variation in IQ. Such putative predictors have included temperature and skin colour (Templer & Arikawa, 2006), evolutionary novelty (Kanazawa, 2008), irreligion (Lynn, Harvey, & Nyborg, 2009), inbreeding (Woodley, 2009) and a range of economic factors (e.g. Dickerson, 2006).…”

“…Previously, the relationship between temperature and national mean IQ has been explained in terms of the greater cognitive demands of surviving in colder environments (Templer & Arikawa, 2006). Given the strength of evidence for the physiological effects of disease, it may be that temperature is acting not through an impact on the environment but through an impact on the interaction between humans and their diseases.…”

“…Kanazawa proposes that this requirement for greater intelligence is what selected for higher-IQ individuals in locations further from the environment of evolutionary adaptedness (EEA).  Temperature (Kanazawa, 2008;Templer & Arikawa, 2006) In a similar hypothesis, a variety of authors have suggested that cold weather and harsh winters select for higher intelligence to be able to cope with the extremes of climate.…”

Genomic ancestry, cognitive ability, and socioeconomic outcomes

“…Perhaps the most widely proposed model is cold winter's theory, which is simply the idea that surviving in colder climates is more cognitive demanding than living in warmer climates and hence there should be (additional) selection for cognitive ability (Lynn, 2015;Rushton, 2000;Templer & Arikawa, 2006;Templer & Stephens, 2014). The model came out by comparing national climate data with national IQs which revealed that winter temperatures were the strongest correlate.…”