Countries and intelligence
Construct for the Social Sciences
The relationship between countries and intelligence has been researched from various aspects. There are estimates of average country IQs based on literature reviews of IQ testing in these countries. There are also several international student assessment tests which also allows comparisons of countries.
A large number of studies have used the data sets in order to research associations to other factors such as differences between countries regarding economic growth, crime, politics, and health. Many of these studies have argued that the average cognitive ability of a country is an important explanation for other country characteristics.
"Average IQ values in various European countries"
The 1981 article "Average IQ values in various European countries" by V. Buj is the only international IQ study that over a short time period has compared country IQs using the same IQ test. It was probably done in the 1970s in the capital cities or in the biggest town in 21 European countries and Ghana. The IQ researcher Rindermann (2007) states that it is of dubious quality with scant information regarding how it was done. However, the correlations with the other measures of the cognitive abilities of countries, except the PISA student assessment test, are good.
Books and articles by Lynn and Vanhanen
The 2002 book IQ and the Wealth of Nations by Richard Lynn and Tatu Vanhanen listed average country IQ for all the countries of the world. This was based on a literature review of earlier IQ testing in many countries. For other countries the average IQ was estimated based on IQ in surrounding countries. Scores were adjusted for several factors such as the Flynn effect.
Lynn and Vanhanen have thereafter published several new articles and books that have updated and greatly expanded the data and estimates as well as answered various criticisms. These updates and expansions include the 2006 book IQ and Global Inequality, the 2010 article "National IQs updated for 41 Nations", and the 2012 book Intelligence: A Unifying Construct for the Social Sciences.
Articles regarding sub-Saharan Africa
The 2009 article "A systematic literature review of the average IQ of sub-Saharan Africans" by Wicherts et al. was critical of Lynn and Vanhanen's estimates regarding sub-Saharan Africa and found somewhat higher average IQs in this region (but not in other regions).
The article was followed by several others regarding sub-Saharan Africa. See the section "Debate regarding sub-Saharan Africa" below.
International student assessment tests
There are several international student assessment tests:
- Trends in International Mathematics and Science Study (TIMSS)
- Programme for International Student Assessment (PISA)
- Progress in International Reading Literacy Study (PIRL)
Rindermann (2007) stated that the correlations between international student assessment tests and Lynn and Vanhanen's country IQs are very high. He found statistical evidence for that the "student achievement assessments and intelligence tests primarily measure a common cognitive ability". Several other tests have reached similar results.
Furthermore, the average IQ of the country of origin of immigrants predicts PISA scores for immigrants in 17 countries.
Lynn and Vanhanen's country IQs predicts for groups from different countries
- Graduate Management Admission Test (GMAT) scores
- Graduate Record Examinations (GRE) scores
- Test of English as a Foreign Language (TOEFL) scores
- 19th and early 20th century numeracy rates for different countries (age heaping)
- Immigrant grade point average in the US
- Immigrant SAT/ACT scores in the US
Debate regarding the reliability and validity of the IQ scores
Calculating the IQ averages involves many choices. Sometimes a study is clearly not representative of the general population or is otherwise problematic. Then there is a choice between ignoring the study or adjusting the results which involves more choices. The IQ of countries with no studies may be calculated by using the results from other countries. Then there is a choice between using the IQs of neighboring countries or the IQs of racially similar countries. Another consideration is that an absence of IQ tests may be due to factors such as extreme poverty that may also affect IQ. The Flynn effect refer to the observed slow increase in IQ scores. Old test scores have to be adjusted for this but it is unclear if the effect is equally strong in all parts of the world which is often the choice made. Different IQ test using different methods and scales have to be translated into comparable scores. Sometimes very small studies are the only one(s) available. The compiling and calculating can introduce simple mistakes. These choices and problems have not surprisingly been criticized and also supporters agree that they make the results more uncertain.
Regarding possible test bias, see Race and intelligence: The genetics or not debate: Test bias.
The average country IQ scores have been defended as reliable since when several IQ test results were available for the same country, then these results were very similar. Regarding the scores for the nations without IQ test results of their own, these have been defended by noting that in many cases such IQ test results were found in later reviews. These later found test results were found to correspond very closely to the earlier scores calculated from neighboring countries IQ. The close correlation with the results from the international student assessment tests have been seen as evidence for the validity of the average country IQ scores. Similarly, see the above section "Other cognitively related tests and measurements".
The many and strong correlations with important country and immigrant variables, as discussed below in the section "Associations with other variables", have also been seen as evidence for that the IQ scores measure something important.
Another response is that is also possible to look at larger areas than individual countries (such as areas predominantly inhabited by particular races). This may greatly increase the number of test results for each examined area/group. If the many test results for such a larger area all show similar results, then this may be argued to support the accuracy of the average IQ value of the larger region.
Lynn and Vanhanen have also responded to the early criticisms in their later works. Thus, simple mistakes done during the compilation have been corrected. The data and studies included in the literature reviews have been greatly expanded in their later works, in part due to new studies being done, in part due to discovering old studies.
A 2013 study examined the average IQ of immigrants to Denmark based on the results of IQ testing done during the military draft. The average measured IQ of non-Western immigrants was 86.3. Based on the IQ scores given in Intelligence: A Unifying Construct for the Social Sciences, the average IQ of this group should be 86.7. The study argued that this "strongly validates Lynn and Vanhanen's national IQs."
Debate regarding sub-Saharan Africa
As noted above, the paper "A systematic literature review of the average IQ of sub-Saharan Africans" by Wicherts et al. (2009) argued for somewhat higher IQ values for sub-Saharan African countries. The authors made an independent literature review and argued that a number of studies showing higher IQ values for sub-Saharan Africa had been excluded by IQ and Global Inequality. The average for all of Sub-Saharan Africa is close to 80 in their calculation. They also argue that the IQ values in the book for sub-Saharan Africa are inconsistent with the results from the student assessment tests. However, they also write that studies looking at the correspondence between the student assessment tests and the IQ tests "appear to validate country IQs in other parts of the world."
Richard Lynn and Gerhard Meisenberg (2009) replied that "critical evaluation of the studies presented by WDM shows that many of these are based on unrepresentative elite samples" and argued that the book values do are consistent with the international student assessment tests also for sub-Saharan Africa. They argued for "an IQ of 68 as the best reading of the IQ in sub-Saharan Africa".
The 2013 study "African cognitive ability: Research, results, divergences and recommendations" by Heiner Rindermann discussed the above mentioned debate regarding sub-Saharan Africa and gave new data and estimates. The article stated that "the best guess for an African average is IQ 75."
A 2016 study has been argued to support Lynn's estimate.
The Unz debate
Ron Unz in 2012 criticized Lynn and Vanhanen's books for, in his opinion, large variability regarding test score results and for the results supporting that decreased poverty has caused a rapid increase in average IQ. Lynn and others have argued against this. This debate has not occurred in academic sources but in various blogs and blog comments.
Debate regarding the reliability and validity of the international student assessment tests
The international student assessment tests have the advantages of standardized and often very recent testing of a very large number of people over a short time period.
Disadvantages include fewer countries than for the IQ test data and only students being tested. Country organizers sometimes differ in implementation and exclusion rates differ. In some countries school attendance is low. The Flynn effect has to be adjusted for although the effect is small for recent tests.
Causes of the country IQ differences
What causes the country IQ differences is often seen as one part of the debate regarding the causes of racial IQ differences. It is generally agreed that some factors such iodine deficiency and other forms of malnutrition which are not significantly important in the developed world lowers IQ for many people in the developing world. This is argued by for example Lynn and Vanhanen in their books to be an explanation for why Africans in Africa score lower than in the United States.
A country is not necessarily racially homogeneous in which case the average country IQ may reflect the different average IQs of the races inhabiting the country and their relative population sizes. Lynn and Vanhanen argue in their books that large scale immigration from countries with low average IQ is lowering the average national IQ of some countries with high average IQ.
Associations with other variables
A large number of academic publications by many different researchers have used the IQ scores for further research. Lynn and Vanhanen in a 2012 literature review described 244 different correlations with other factors that had been stated in scientific studies.
Many of these studies have not just found correlations but often also argued for IQ being a causal factor in the relationships based on more advanced statistical methods as well as other kinds of evidence.
Examples of variables that correlate with a higher average country IQ:
- Higher gross domestic product/capita
- Higher economic growth
- Lower income inequality (Gini Index)
- Lower share living on less than $2 each day
- Lower unemployment
- Higher savings as share of gross domestic product
- Higher investments as share of gross domestic product
- Higher "Human Development Index"
- Lower share of population working with agriculture
- Less corruption
- Highers rankings on different measures of democracy
- Higher political freedom
- Better "rule of law"
- Better laws and institutions
- Lower rankings on the "Failed States Index"
- Longer life expectancy
- Less malnutrition
- Lower infant mortality
- Lower maternal mortality
- Less HIV/AIDS
- Less infectious diseases
- More suicide
- Lower population growth
- Lower share of youths in the population
- Less polygamy
Education and science
- Higher literacy
- Longer education
- More academic publications
- More patents
- More scientists and researchers
- Lower share who describe themselves as religious
- Lower share who state that religion is important
- Higher share of atheists
- Fewer cases of deadly violence
- Fewer cases of assault
- Fewer cases of rape
- Higher income in the United States for immigrants from higher IQ countries
- Higher share in Norway being self-employed for immigrants from higher IQ countries
Associations in studies described in Intelligence: A Unifying Construct for the Social Sciences
- "Acquiescence" - defined as agreement with statements presented in opinion surveys. People in low IQ countries were more likely to "acquiesce".
- "Extremity" - defined as the preferential use of the end points of the scale when not asked to agree or not with statements but instead to indicate viewpoint on a scale. People in low IQ countries were more likely to be "extreme".
- "Speed of life" - "the speed of service at post offices, walking speed and the accuracy of clocks." High IQ countries were more likely to have a higher "speed of life".
- "War" - "measured as participation, intensity and destructive effects of war in the years 1960-2000, including civil wars. The negative correlation shows that high IQ countries have less engagement in war. The correlation is low but statistically significant."
- "Time preference" - "Time preference was measured by responses to the question "Would you prefer $3400 this month or $3800 next month?" Choosing the second option indicates low time preference or in psychological terms, present-orientation, delay discounting and a capacity to delay gratification." Time preference was lower in high IQ countries in a study of 10 Asian countries.
- "Son preference". - "a low but statistically significant positive correlation of 0.18 between national IQ and son preference." This may be due to these countries being wealthier since there is an argued preference for sons in such societies according to the evolutionary Trivers–Willard hypothesis.
- "Modernism" and "post-modernism". These are described as sets of liberal values. "The positive correlations show that countries with higher IQs have stronger Modernist and Post-Modernist values." Lower income equalities as measured with the Gini coefficient in countries with higher IQs have also been interpreted as being due to support for liberal values. See also Political correctness: IQ and political correctness and Other race differences: Values.
Associations in later studies
- More science-like thinking e.g. no belief in magic (Piagetian based epistemic rationality).
- Higher trust.
- Higher happiness. Some early studies found no significant correlations but several later have, in particular for poor countries and for individualistic countries.
- Lower happiness inequality.
- A 2015 study stated that the cognitive ability of the society as a whole, but in particular the cognitive ability of the intellectual class (defined as those scoring in top 5% on cognitive tests), and to a minor degree the cognitive ability of leading politicians, influences government governance, which in turn has various positive effects for society. See also Smart fraction.
- A 2016 study stated that higher average country intelligence is associated with less deforestation as well as stating that "The main implication from our study is that intelligence not only shapes formal rules and informal regulations such as social trust, norms and traditions but also it has the ability to reverse the paradoxical process known as “resource curse”."
- A 2016 study stated that "Extant literature on the link between patent protection and economic growth have yielded inconclusive results.... we find that patent protection has positive effect on growth only after accounting for the interaction between IQ and IPR."
- A 2017 study stated that "Previous research has found that there is a statistically significant, positive link between country-level IQ and various measures of aggregate production, such as GDP. This study extends that analysis by estimating the relationship between IQ and a new measure of economic welfare. Developed by Jones and Klenow (2016), welfare is not a measure of spending on public assistance programs, but a theory-based empirical construct combining several metrics of economic well-being. Using this new economic welfare index for a large sample of countries (74), we find that IQ is a statistically significant (5% or better) and economically important predictor of welfare growth. A one-point increase in IQ is associated with a 4% increase in welfare growth for the average country. Our results support the view that national IQ is an important determinant of cross-country differences in economic activity and welfare."
"Limits to democratization"
The 2009 book Limits to democratization stated that "all nations do not have equal chances to establish and maintain democratic systems. A central conclusion is that it is probably never possible to achieve the same level and quality of democracy in all countries of the world because of the impact of the two ultimate constraining factors (annual mean temperature and national IQ), which are outside conscious human control."
Average IQ differences between different US states and counties, in part reflecting the racial composition, have been argued to be an important explanation for differences regarding economic performance, gross state product, government effectiveness, health, suicide, crime, birth rate, infant mortality, life expectancy, and HIV/AIDS.
A 2015 study stated that "Many recent studies have examined within-country regional correlates of (general) cognitive ability (also known as (general) intelligence, general mental ability, g). This has been done for the British Isles (Lynn, 1979; Kirkegaard, 2015g), France (Lynn, 1980), Italy (Lynn, 2010; Kirkegaard, 2015e), Spain (Lynn, 2012), Portugal (Almeida, Lemos, & Lynn, 2011), India (Kirkegaard, 2015d; Lynn & Yadav, 2015), China (Kirkegaard, 2015f; Lynn & Cheng, 2013), Japan (Kura, 2013), the US (Kirkegaard, 2015b; McDaniel, 2006; Templer & Rushton, 2011), Mexico (Kirkegaard, 2015a) and Turkey (Lynn, Sakar, & Cheng, 2015). This paper examines data for Brazil."
See also the article on the differential K theory on studies finding that many within-country variables varying on a north-south gradient in several examined countries as predicted by the differential K theory.
Important non-IQ causes of country differences
IQ is not the only factor causing important differences between countries.
Lynn has argued that Northeast Asians, despite having slightly higher average country IQs, have produced much less creative discoveries and innovations in the arts and sciences than Europeans. One possibly explanation is that East Asians have lower average creativity than Europeans. Lynn argues that this is supported by Northeast Asians scoring lower on the personality trait openness to experience.
Communist rule caused affected countries to underperform compared to their average IQ which was demonstrated in IQ and the Wealth of Nations. It is also demonstrated by the different performance of several neighboring countries with people of the same race: East Germany vs. West Germany, North Korea vs. South Korea, and China (before economic reforms) vs. Taiwan and Hong Kong.
Another IQ map, with different colored highlighting
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 Rindermann,H. (2007). The g-factor of international cognitive ability comparisons: The homogeneity of results in PISA, TIMSS, PIRLS and IQ-tests across nations. European Journal of Personality, 21, 6 67-706 http://onlinelibrary.wiley.com/doi/10.1002/per.634/abstract
- ↑ Buj, V. (1981). Average IQ values in various European countries. Personality and Individual Differences, 2, 168–169
- ↑ Richard Lynn and Tatu Vanhanen. IQ and Global Inequality. 2006. Washington Summit Publishers.
- ↑ Richard Lynn. Mankind Quarterly. Vol. 50, No. 4 (Summer 2010) pp. 275-296, "National IQs updated for 41 Nations". http://www.mankindquarterly.org/summer2010_lynn.html
- ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 Richard Lynn & Tatu Vanhanen. Intelligence: A Unifying Construct for the Social Sciences. 2012. Ulster Institute for Social Research.
- ↑ 6.0 6.1 Jelte M. Wicherts, Conor V. Dolana, and Han L.J. van der Maas, A systematic literature review of the average IQ of Sub-Saharan Africans, Intelligence, Volume 38, Issue 1, January–February 2010, Pages 1-20, http://dx.doi.org/10.1016/j.intell.2009.05.002
- ↑ 7.0 7.1 7.2 7.3 7.4 Lynn, R., & Vanhanen, T., National IQs: A review of their educational, cognitive, economic, political, demographic, sociological, epidemiological, geographic and climatic correlates, Intelligence (2012), http://dx.doi.org/10.1016/j.intell.2011.11.004
- ↑ 8.0 8.1 8.2 8.3 John Fuerst. L&V’s National IQs predict 2011-2012 GRE scores for 114 citizenship groups, 2010 + 2012 TOEFL scores for 157 citizenship groups, PISA scores of migrants from 62 nations of origin across 17 destination nations, 19th century (birth cohort 1820) numeracy rates across 54 nations, and early 20th century (birth cohort 1890) numeracy across 129 nations. Human Varieties, 2014. http://humanvarieties.org/2014/02/11/lvs-2012-national-iqs-predict-2011-2012-gre-scores-for-114-citizenship-groups-2010-2012-toefl-scores-for-157-citizenship-groups-pisa-scores-of-migrants-from-62-nations-of-origin-across-1/
- ↑ John Fuerst. Quick Post: L&V’s National IQs predict GMAT scores across 173 nations. Human Varieties, 2014. http://humanvarieties.org/2014/02/02/quick-post-lvs-national-iqs-predicts-gmat-scores-across-173-nations/
- ↑ 10.0 10.1 Do National IQs Predict U.S. Immigrant Cognitive Ability and Outcomes? An Analysis of the National Longitudinal Survey of Freshman. Open Differential Psychology, 2014. http://openpsych.net/ODP/2014/04/do-national-iqs-predict-u-s-immigrant-cognitive-ability-and-outcomes-an-analysis-of-the-national-longitudinal-survey-of-freshman/
- ↑ Kirkegaard, Emil OW. "Predicting Immigrant IQ from their Countries of Origin, and Lynn's National IQs: A Case Study from Denmark." Mankind Quarterly, Vol. 54, No. 2 (Winter 2013) pp. 151-167 http://www.mankindquarterly.org/winter2013_kirkegaard.html
- ↑ The dangers of unsystematic selection methods and the representativeness of 46 samples of African test-takers, Jelte M. Wicherts, Conor V. Dolana and Han L.J. van der Maas, Intelligence Volume 38, Issue 1, January–February 2010, Pages 30-37 http://dx.doi.org/10.1016/j.intell.2009.11.003
- ↑ "The average IQ of sub-Saharan Africans: Comments on Wicherts, Dolan, and van der Maas", Richard Lynna and Gerhard Meisenberg, Intelligence, Volume 38, Issue 1, January–February 2010, Pages 21-29 http://dx.doi.org/10.1016/j.intell.2009.09.009
- ↑ Heiner Rindermann, African cognitive ability: Research, results, divergences and recommendations, Personality and Individual Differences, Volume 55, Issue 3, July 2013, Pages 229-233, ISSN 0191-8869, http://dx.doi.org/10.1016/j.paid.2012.06.022
- ↑ Africa and the cold beauty of Maths https://drjamesthompson.blogspot.co.uk/2016/12/africa-and-cold-beauty-of-maths.html
- ↑ Ron Unz. Race, IQ, and Wealth. The American Conservative. http://www.theamericanconservative.com/articles/race-iq-and-wealth/
- ↑ Richard Lynn. IQ and the Wealth of Nations: Richard Lynn Replies to Ron Unz. August 3, 2012, 3:57 am. Vdare. http://www.vdare.com/articles/iq-and-the-wealth-of-nations-richard-lynn-replies-to-ron-unz
- ↑ David Sanders. Has Ron Unz Refuted “Hard Hereditarianism”? July 21, 2012, 7:29 am http://www.vdare.com/articles/has-ron-unz-refuted-hard-hereditarianism
- ↑ Helmuth Nyborg. Helmuth Nyborg’s Reply to Ron Unz By on August 3, 2012, 3:49 am. http://www.vdare.com/articles/helmuth-nyborg-s-reply-to-ron-unz
- ↑ The Hispanic Asian Flynn Effect. Sunday, August 5, 2012. http://theunsilencedscience.blogspot.no/2012/08/the-hispanic-asian-flynn-effect.html
- ↑ John Fuerst, Various posts. https://z139.wordpress.com/2012/08/29/redebunking-ron/ https://z139.wordpress.com/2013/06/02/the-argument-ron-should-have-made/ https://z139.wordpress.com/2013/05/21/ron-unz-on-richwines-argument-taking-the-bull-by-the-horn/
- ↑ Peter Frost. Various posts. http://www.evoandproud.blogspot.ca/2012/07/ron-unz-on-race-iq-and-wealth.html, http://www.evoandproud.blogspot.ca/2012/07/more-on-race-iq-and-wealth.html, http://www.evoandproud.blogspot.ca/2012/08/he-who-pays-piper.html
- ↑ Cronk, L. (2007). "Boy or girl: Gender preferences from a Darwinian point of view". Reproductive BioMedicine Online 15: 23–32. doi:10.1016/S1472-6483(10)60546-9. PMID 18088517.
- ↑ Heiner Rindermann, Luisa Falkenhayn, Antonia E.E. Baumeister, Cognitive ability and epistemic rationality: A study in Nigeria and Germany, Intelligence, Volume 47, November–December 2014, Pages 23-33, ISSN 0160-2896, http://dx.doi.org/10.1016/j.intell.2014.08.006. http://www.sciencedirect.com/science/article/pii/S016028961400124X
- ↑ Noah Carl, Does intelligence explain the association between generalized trust and economic development?, Intelligence, Volume 47, November–December 2014, Pages 83-92, ISSN 0160-2896, http://dx.doi.org/10.1016/j.intell.2014.08.008. http://www.sciencedirect.com/science/article/pii/S0160289614001275
- ↑ Maciej Stolarski, Dorota Jasielska, Marcin Zajenkowski. (2015). Are all smart nations happier? Country aggregate IQ predicts happiness, but the relationship is moderated by individualism–collectivism. Intelligence, Volume 50, May–June 2015, Pages 153–15. https://www.sciencedirect.com/science/article/pii/S0160289615000501
- ↑ Nikolaev, B., & Salahodjaev, R. (2016). The role of intelligence in the distribution of national happiness. Intelligence, 56, 38-45. http://www.sciencedirect.com/science/article/pii/S0160289616300666
- ↑ Heiner Rindermanna, Oasis Kodila-Tedika, Gregory Christainsen. (2015). Cognitive capital, good governance, and the wealth of nations Intelligence, Volume 51, July–August 2015, Pages 98–108. https://www.sciencedirect.com/science/article/pii/S0160289615000781?np=y
- ↑ Obydenkova, A., Nazarov, Z., & Salahodjaev, R. (2016). The process of deforestation in weak democracies and the role of Intelligence. Environmental Research, 148, 484-490. http://www.sciencedirect.com/science/article/pii/S0013935116301207
- ↑ Odilova, S. (2016). Patent protection, intelligence and economic growth: a cross-country empirical investigation. Journal of Research in Business, Economics and Management, 6(1), 798-803. http://scitecresearch.com/journals/index.php/jrbem/article/view/746
- ↑ New estimates on the relationship between IQ, economic growth and welfare http://www.sciencedirect.com/science/article/pii/S016028961630318X
- ↑ Tatu Vanhanen. (2009) The Limits of Democratization: Climate, Intelligence, and Resource Distribution. Atlanta, GA: Washington Summit Publishers.
- ↑ Satoshi Kanazawa, IQ and the wealth of states, Intelligence, Volume 34, Issue 6, November–December 2006, Pages 593-600, ISSN 0160-2896http://dx.doi.org/10.1016/j.intell.2006.04.003
- ↑ Satoshi Kanazawa, IQ and the health of states, Biodemography and Social Biology, Vol. 54, Iss. 2, 2008 http://dx.doi.org/10.1080/19485565.2008.9989142
- ↑ Martin Voracek. (2008) State IQ and Elderly Suicide Rates in the United State. Psychological Reports: Volume 102, Issue , pp. 601-602. http://dx.doi.org/10.2466/pr0.102.2.601-602
- ↑ Jared M. Bartels, Joseph J. Ryan, Lynn S. Urban, Laura A. Glass, Correlations between estimates of state IQ and FBI crime statistics, Personality and Individual Differences, Volume 48, Issue 5, April 2010, Pages 579-583, ISSN 0191-8869, http://dx.doi.org/10.1016/j.paid.2009.12.010.
- ↑ Donald I. Templer, J. Philippe Rushton, IQ, skin color, crime, HIV/AIDS, and income in 50 U.S. states, Intelligence, Volume 39, Issue 6, November–December 2011, Pages 437-442, ISSN 0160-2896, http://dx.doi.org/10.1016/j.intell.2011.08.001.
- ↑ Kevin M. Beaver, John Paul Wright, The association between county-level IQ and county-level crime rates, Intelligence, Volume 39, Issue 1, January–February 2011, Pages 22-26, ISSN 0160-2896, http://dx.doi.org/10.1016/j.intell.2010.12.002.
- ↑ (2006) "Estimating state IQ: Measurement challenges and preliminary correlates". Intelligence 34 (6): 607–619. doi:10.1016/j.intell.2006.08.007. ISSN 01602896.
- ↑ Kirkegaard, E. O. W. (2015). The S factor in Brazilian states. The Winnower. https://thewinnower.com/papers/the-s-factor-in-brazilian-states
- ↑ Richard Lynn, Race Differences in Intelligence, Creativity and Creative Achievement, Richard Lynn, Mankind Quarterly, Vol. 48, No. 3 (Spring 2008) pp. 299-309, http://www.mankindquarterly.org/spring2008_lynn.html