Race and intelligence

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Race and intelligence
Race and intelligence: The genetics or not debate
Countries and intelligence
Race and morphology/physiology
Race and sports
Differential K theory
Human Accomplishment
Other race differences
Related research areas
Boasian anthropology
Contact hypothesis
Effects of race mixing ‎
Ethnic heterogeneity
Ethnic nepotism
Genetics denialism
Inbreeding depression and
outbreeding depression
Pathological altruism
Smart fraction
The sociologist's fallacy
White flight
White demographics
Intelligence quotient
Race and intelligence
Countries and intelligence
Intelligence: A Unifying
Construct for the Social Sciences

The relationship between race and intelligence has been the subject of a large and complex scientific and public debate often influenced by political correctness. Human races/ethnicities differ on average measured IQ according to large scale testing. The role of genetics as a cause for these measured differences has been examined in numerous scientific studies. The differences are argued to be responsible for numerous important societal effects.



Race differences in intelligence was historically a common view. For example, Muslim writers stated low intelligence among Blacks.[1][2]

Early scientific research started in the nineteenth century and included methods such as skull and brain measurements.[3]

Francis Galton, half-cousin of Charles Darwin and an important eugenicist and differential psychologist, was also an important early pioneer in intelligence research as well as race and intelligence research. Arthur Jensen has stated that "Although the conclusions Galton drew from his empirical studies were seldom compelling for lack of the needed technology and methods of statistical inference in his day, contemporary research has generally borne out most of Galton’s original and largely intuitive ideas".[4]

The first IQ test was created in 1905. By the end of the twentieth century many hundreds of studies measuring the IQs of racial/ethnic groups had been published.[3] The number of studies discussing these results is much larger.

Race research in general, including also race and intelligence research, became increasingly a taboo subject after WWII. During this time the Pioneer Fund was influential in keeping some research and debate alive.

In 1969 Arthur Jensen caused great public controversy with the article "How Much Can We Boost IQ and School Achievement?" in which he argued for genetics being an important explanation for the measured differences.[5][6]

In 1987 a survey of the opinion of IQ experts was published. One question concerned what caused the US Black-White IQ gap. The survey found a large support for a partial genetic, partial environmental explanation. The survey was later used in the book The IQ Controversy, the Media and Public Policy (1988) which argued that the general public was misled by the media regarding the expert opinion.[7][8]

Further public debate ensued after the publication in 1994 of The Bell Curve which argued for the existence of race differences in IQ as well as stating that this is an important explanation for many social differences between the races such as regarding crime, education, unemployment, etc.

In response to the Bell Curve debate and perceived false and highly misleading views in the public debate, the statement "Mainstream Science on Intelligence" was signed by 52 professors.

The American Psychological Association also responded to the debate by creating a committee which in 1995 published the report "Intelligence: Knowns and Unknowns" which acknowledged the gap between the average IQ scores of Whites and Blacks, the importance of IQ, and stated that both genetic and environmental explanations had inadequate support. It concluded "In short, no adequate explanation of the differential between the IQ means of Blacks and Whites is presently available."

Jensen commented that "As I read the APA statement, [...] I didn't feel it was contradicting my position, but rather merely sidestepping it. It seems more evasive of my position than contradictory. The committee did acknowledge the factual status of what I have termed the Spearman Effect, the reality of g, the inadequacy of test bias and socioeconomic status as causal explanations, and many other conclusions that don't differ at all from my own position. [...] Considering that the report was commissioned by the APA, I was surprised it went as far as it did. Viewed in that light, I am not especially displeased by it."[9]

The debate also caused other responses such as popular science books aimed at the general public. The Jewish Stephen Jay Gould published a second edition of The Mismeasure of Man (originally published in 1983) and the Jewish Jared Diamond published Guns, Germs, and Steel in 1997. Both denied genetically caused racial IQ differences, both became international bestsellers among the general public, and both were translated into numerous languages. Their impacts on the academic debate among IQ researchers were much smaller. (More generally regarding the views of Jewish scientists on genetic race differences, see Arguments regarding the existence of races: Views of scientists.)

The 2000s saw a widening of the debate from mainly being about US racial differences to also more systematically include worldwide racial differences. Richard Lynn published several books which systematically reviewed earlier worldwide IQ testing. He estimated the average IQs of races and the average IQ of countries as well as argued for many and important practical effects due to the IQ differences. Many other researchers have published further studies on these subjects.

In 2013 another survey of expert opinion was done. It and the 1987 survey are discussed in more detail below in the sections "Opinion of experts in 1987" and "Opinion of experts in 2013".

Another trend is the continued rapid advance in genetic research which may in the near future definitely settle the debate regarding whether the measured racial IQ differences are partially genetic or not.

Measured average IQs

Note that the below values are measured average IQs for different groups according to the given sources. Individuals may differ greatly from these values and individuals with high and low IQs exist in all groups.


Average national IQs according to IQ and the Wealth of Nations. Later estimates by the same authors are largely similar. See Intelligence: A Unifying Construct for the Social Sciences for recent values. Note that many countries are racially heterogeneous.

Richard Lynn in his 2006 book Race Differences in Intelligence reviewed the literature on worldwide IQ testing and calculated the average IQs for different races based on earlier IQ test results (citing hundreds of different studies testing the average IQ of different races).

Race: Measurement region Measured average IQ Number of samples Number of countries
Aborigines: Australia 62 17 1
Aborigines: New Guinea 63 5 1
Amerindians: North America 86 19 2
Amerindians: Latin America 86 10 5
Arctic Peoples: North America 91 15 2
Bushmen: South West Africa 54 3 1
East Asians: East Asia 105 60 7
East Asians: United States 101 26 1
East Asians: Elsewhere 102 9 5
Europeans: Europe 99 71 25
Europeans: Outside Europe 99 23 12
Pacific Islanders: Pacific Islands 85 14 9
Pacific Islanders: New Zealand 90 12 1
South Asians and North Africans: South Asia 84 37 17
South Asians and North Africans: Britain 92 16 1
South Asians and North Africans: Europa 85 18 3
South Asians and North Africans: Africa 86 6 2
South Asians and North Africans: Fiji, etc 85 3 3
Southeast Asians: Southeast Asia 87 11 6
Southeast Asians: United States 93 7 1
Sub-Saharan Africans: Africa 67 57 17
Sub-Saharan Africans: Caribbean 71 14 6
Sub-Saharan Africans: United States 85 29 1
Sub-Saharan Africans: Netherlands 85 7 1
Sub-Saharan Africans: Britain 86 18 1

These are measured (phenotypic) average IQs. Differences for the same race between regions were explained by factors such as malnutrition being prevalent in developing nations, race mixing, as well emigrants for a variety of reasons possibly having different average IQ than that of their region of origin. Thus, Lynn estimated that the genotypic average IQ of Sub-Saharan Africans is 80 rather than the measured phenotypic 67. The genotypic average IQ of Blacks in the United States was estimated to be somewhat higher at 85 due to some interbreeding with Europeans.[3]

There were also some groups differences regarding the profile of narrower mental abilities. East Asians and Amerindians had a pattern of relatively high non-verbal reasoning/spatial IQ and relatively low verbal IQ (compared to the overall average measured IQs of the groups).[3]

Regarding various criticisms and counter-criticisms of such literature reviews and measured average IQ scores (in particular the average measured IQ of Sub-Saharan Africa), see the related discussions in the article about Countries and intelligence.

Very large scale international student assessment tests are regularly performed in many countries. Such testing may often be much larger and more recent than formal IQ testing. These and other country level tests may not directly test racial differences but results from such testing are sometimes used for indirect or related studies. Again see the article Countries and intelligence.

World average IQ

The average IQ of the world as of 2000 has been estimated to be 90 based on estimated average country IQs and country population sizes.[10]

United States Black-White gap

The Black-White IQ gap according to studies done over nearly a hundred years. Each dot represents a study. The Black-White IQ gap was in 2012 stated to have decreased by at most 0.2 SD.[11]
Diagram illustrating Wechsler Adult Intelligence Scale IV full-scale IQ score distributions for racial and ethnic groups in the United States. Note that the population sizes of the different groups are not shown in the diagram. Most group members score near the average group value but there are some members who score much higher and much lower in all groups. Another characteristic is that relative group differences are increasingly more amplified at more extreme IQ values (see Arguments regarding the existence of races: Average vs. extreme groups differences).

Review articles by Rushton and Jensen (2005 and 2010) stated that in the United States, Blacks and Whites have been the subjects of the greatest number of studies. These studies have shown that the Black-White IQ difference is about 15 to 18 points or 1 to 1.1 standard deviations (SDs).[12][6]

Such a difference means that the White average IQ is higher than that of 80-85% of Blacks.[6] However, it should be noted that for "bell curve" distributions ("normal distributions"), such as for IQ and many other traits, if there is an average difference between two groups, then it will be amplified at the extremes. One example is regarding height where the men:women ratio becomes increasingly larger with increasing height. Similarly, IQ differences will be most pronounced at extreme IQs.[13]

The 1996 America Psychological Association's report "Intelligence: Knowns and Unknowns" and the 1994 statement "Mainstream Science on Intelligence" gave similar numbers.[14][15]

Roth et al. (2001) in a meta-analysis reviewed the results of over 6 million participants on tests of cognitive ability or aptitude found a Black-White gap of 1.1 SD. Consistent results were found for college and university application tests such as the Scholastic Aptitude Test (N = 2.4 million) and Graduate Record Examination (N = 2.3 million), as well as for tests of job applicants in corporate sections (N = 0.5 million) and in the military (N = 0.4 million).[16]

Some studies have argued that the gap has narrowed by up to a third but has been criticized for selective exclusion of opposing results, incorrect calculations, or for this occurring on the tests measuring the g factor less well. If a narrowing has occurred, then it may have stopped in recent times. Some narrowing is compatible with the gap being partly environmental. Other studies have found no narrowing. The meta-analytic review by Roth et al. stated that any narrowing was "either small, potentially a function of sampling error...or nonexistent for highly g loaded instruments”.[12][17]

See also the section Race and intelligence: The genetics or not debate: Shared and unshared environmental factors regarding the gap being argued to have narrowed for children, and especially young children, but this narrowing almost completely disappearing as the individuals age.

A 2013 review stated that "a gap of 1 full standard deviation is already apparent on IQ tests at 36 months of age, and that there has been no obvious convergence in this early performance difference over time."[18]

A factor which could possible cause a change in average cognitive ability score for a group (including immigrant groups) is if an increasing number of mixed-race individuals tend to identify themselves as members of this group (such as mixed Black-White individuals tending to identify themselves as Black). However, such a cognitive ability score change could reflect the average genetics of the group changing.

Another view is that the Black-White IQ is actually larger than 1 SD and that the average Black IQ is likely 78 (a 22 point Black-White gap). This is argued to be supported by testing such as the military draft testing during WWII which is argued to be the most representative testing ever done. It is argued that higher results than 78 may be due to unrepresentative samples caused by factors such as non-participation in voluntary testing by the very lowest scoring segments of the Black population in inner cities.[12]


The US group "Hispanics" is a diverse group that may have Amerindian, European, and Sub-Saharan African origins in varying proportions. Most are of mixed Amerindian/European origin.

In the US the tested average IQ of "Hispanics" is typically intermediate between that of Blacks and Whites.[14] Both the above mentioned 2001 meta-analysis and the book Race Differences in Intelligence found an average IQ of 89.[3]


Main article: Jews and intelligence


Several studies of the IQ of Gypsies, a people of South Asian origin living in Europe since several centuries but with little intermarrying with other groups, have found average IQs ranging from 70 to 83.[19] A 2015 meta-analysis stated an average IQ of 74.[20]

See also Gypsies: Intelligence.


Several studies have stated that the measured cognitive ability test scores of immigrants are generally similar to those from their region of origin and that this generally persists for at least several generations. There are also discussions regarding some specific immigrant groups such as West Indians of African origin immigrants to United States and African immigrants to the United Kingdom. See Race and intelligence: The genetics or not debate: Immigrants on this topic.

Historical differences

The book The Nature of Race: the Genealogy of the Concept and the Biological Construct’s Contemporaneous Utility stated that "As Baten and Juif (2013) note, the international cognitive ability differences are not new and they precede the event of mass schooling. As such, Baten and Sohn (2013) found that Korea, China and Japan had high numeracy levels in the 1600s; Juif and Baten (2013) found that Spanish and Portuguese had higher numeracy levels than Amerindian Incas in the 1500s. Juif and Baten (2013) also found that 1820 cohort ethnic/national cognitive ability levels predicted 21st century national levels."[21]

Related variables

There are also several variables associated with IQ which can also be measured (such as brain size, reaction time, and different results on different kinds of tests/subtests) and which have been measured in different groups. They are discussed in the article Race and intelligence: The genetics or not debate‎.

General race and intelligence research issues

Ad hominem, straw men, and guilt by association

Those arguing for a genetic explanation, sometimes referred to as "hereditarians", are frequently subjected to various forms of ad hominem personal attacks. This may include accusations of being "racist" (in some extremely negative sense), associations with claimed "racists", claimed "racists" using the research etc. Obviously ad hominem personal attacks are not scientifically valid arguments regarding what causes the racial IQ differences.

A somewhat more sophisticated ad hominem attack method is more or less openly insinuating that the researchers are bribed by the Pioneer Fund. This despite many hereditarians never having received any research funding by the Pioneer Fund. The argument may then be that these researchers are relying on earlier research funded by the Pioneer Fund. This ignores the often completely independent research done by these researchers. This also ignores that a researcher may have a far easier career and even physical security if being politically correct. One example being that the Nobel Prize winner and discoverer of DNA James Watson was essentially fired for publicly expressing a hereditarian view.[22] Finnish police considered starting a criminal investigation of Tatu Vanhanen, co-author of IQ and the Wealth of Nations, for expressing hereditarian views.[23]

Stephen Jay Gould's book The Mismeasure of Man became an international bestseller. It has been criticized by hereditarians as largely attacking straw men such as problematic results from early intelligence research that are not relevant for the modern debate. The book has been argued to be an attempt to discredit modern research and modern researchers by using guilt by association.[24][25] Furthermore, an important criticism in the book was regarding the early nineteenth century researcher Samuel George Morton. Gould accused Morton of manipulating the results regarding average racial cranial capacities. However, a 2011 study made new measurements of the skulls used by Morton and analyzed Morton's and Gould's claims. The study stated that Morton had not manipulated the results. On the other hand, Gould had done several remarkable errors.[26]

Race research and the origin of racism

See Racism: Race research and the origin of racism.

The existence of races

Denying the existence of races may be used as an attempted argument against race and IQ research. However, it should be noted that even if races in the sense of subspecies were proven to be incorrect, then this does not actually make the debate disappear. It is possible to study IQ differences between groups that are not races (for example, IQ differences between criminals and non-criminals, IQ differences between different age groups, and so on). Even those claiming that races are social constructs still argue that it is possible to study, for example, average income differences between Blacks and Whites, so average IQ differences could also be studied. Simply demanding that a more politically correct label than "race" should be used, such as "ethnicity" or "population", will not change this.

Blacks and Whites differ genetically regarding, for example, the genes for skin color and sickle-cell anemia. So they could differ also regarding IQ genes. Furthermore, IQ is likely affected by a very large number of genes. This means that even if the population differences regarding the population frequencies of individual gene variants affecting IQ are all small, but these population frequencies correlate, then the total effect of many such small but correlated differences may be that the population differences regarding genetic effects on IQ are very large.

It is perfectly possible to study the role of genetics as an explanation for differences between groups that are not subspecies or even between groups that no one has claimed to be races. Current examples would include the enormous amount of medical research regarding the genetic differences between those having a certain disease and those not having this disease.

The genetics or not debate

Recent advances in the knowledge of genetic differences between different populations have made it possible to now directly examine the role of genetics in the measured racial IQ differences and may soon resolve the issue. The table shows predicted genotypic IQs of several populations in developing countries based on genetic population data according to a 2015 study. See Race and intelligence: The genetics or not debate: Direct genetic evidence regarding more details.[27]

The scientific debate regarding whether the measured racial IQ differences (in particular the well-studied US Black-White gap) are partially genetic involves numerous different scientific studies using many different kinds of evidence. It sometimes uses non-trivial mathematics. The debate is discussed in the article Race and intelligence: The genetics or not debate.

This section will only briefly mention two aspects: surveys of expert opinion and the recent direct genetic evidence which may soon resolve the issue.

Opinion of experts in 1987

The 1987 "Survey of Expert Opinion on Intelligence and Aptitude Testing" was published in American Psychologist (the official journal of the American Psychological Association). It surveyed 1020 IQ experts 661 of which completed the questionnaire. One question was "Which of the following best characterizes your opinion of the heritability of black-white differences in IQ?"[7]

  • 14% declined to answer the question.
  • 24% voted that there was insufficient evidence to give an answer.
  • 1% voted that the gap was "due entirely to genetic variation".
  • 15% voted that it "due entirely to environmental variation".
  • 45% voted that it was a "product of genetic and environmental variation".[7]

The survey formed one part of the 1988 book The IQ Controversy, the Media and Public Policy which argued that the public was misled regarding the expert opinion on the issue.[8]

Opinion of experts in 2013

In 2013 a similar survey was presented. Researchers were invited to participate only if they had recent intelligence-related publications in peer-reviewed journals. Invitations were emailed to 1237 persons and at the end 228 (18 %) completed the process (70 fully and 158 partially). As far as the authors could make it out, “lefties” and “righties” turned down the offer in equal numbers.[28]

Asked: What is the influence of average cognitive ability level and highly cognitive competent persons on positive development of society, the economy, technology, democracy and culture?

  • All of the results were above the mid point, suggesting agreement about a positive relationship between high intelligence and social progress.[28]

Asked: What are the sources of U.S. black-white differences in IQ?

  • 0% of differences due to genes: 17%
  • 0-40% of differences due to genes: 42%
  • 50% of differences due to genes: 18%
  • 60-100% of differences due to genes: 39%
  • 100% of differences due to genes: 5%
  • On average for all experts, 47% of the difference was due to genes (SD=31%).[28]

Out of 26 media sources on intelligence, only 3 were rated better than 5 out of 9. Experts rated public debates on intelligence as twice as likely to be ideological than scientific.[28]

Opinion of experts in 2016

A survey published in 2016 surveyed experts who had published articles on or after 2010 in journals on intelligence, cognitive abilities, and student achievement. A total of 1345 people were invited with 71 responding and answering the questions on cross-national cognitive ability differences. Those surveyed were asked to state a percentage rating indicating the importance of 15 possible causes of measured cognitive ability differences.[29]

Many of the 15 possible factors included in the survey may be influenced by genetics and genetic groups differences. The survey did not include a single binary question on which overall factor, genetics or environment, is the more important explanation for the differences.[29] Thus, it cannot be compared in that respect with the 1987 and 2013 surveys.

Also, cross-national differences are not the same as the US Black-White differences asked about in the 1987 and 2013 surveys. Also supporters of a partially genetic explanation generally arguing that environmental factors are more important in developing countries than in developed countries.

"Seventy-one experts rated possible causes of cross-national differences in cognitive ability based on psychometric IQs and student assessment studies (e.g., PISA, PIRLS, TIMSS). Genes were rated as the most important cause (17%), followed by educational quality (11.44%), health (10.88%), and educational quantity (10.20%) [...] Only 5 of 71 experts (7%) who responded to the genetic item thought that genes had no influence. [...] Items with lower percentages (< 10%) included wealth, culture, and modernization (7–9%). Methodological bias factors (sampling error, test knowledge, test bias) were rated as less important (3–6%, together 11.78%). [...] The low ratings for methodological factors suggest that international assessments were perceived to be valid indicators of cognitive ability and cross-country patterns. [...] Because environmental theories are rarely questioned in research, their corroboration by an expert survey is not astonishing. More important is the support for the frequently hotly disputed genetic explanations. Assuming that the survey is representative of expert opinions, genetic factors should receive more attention in future research and public debates."[29]

There were also similar questions on some more specific groups such as "Immigrants from the Middle East (Arabian and Muslim countries) [...] In the current study, experts attributed the low test results primarily to genetic factors (23.01%) and culture (17.26%). Discrimination was rated as relatively unimportant for Middle Eastern immigrants (2.27%) and for other groups and countries (1.25%)."[29]

Evolutionary explanations for racial differences

Scatterplot showing relationships between IQ, brain size, winter temperature, and ice age (Wurm) temperature for populations from different areas based on data from the book "Race differences in Intelligence".[3]

Assuming that the average measured IQ differences are partially due to genetic differences, several evolutionary explanations for these differences have been proposed. One is that living in a cold climate has been argued to be cognitively challenging for much of human history. This is argued to be supported by high correlations between average country IQ and colder average temperature, higher latitude, lighter skin color, and larger cranial cavity volume.[30][31][32]

The book The Nature of Race: the Genealogy of the Concept and the Biological Construct’s Contemporaneous Utility stated that this "model has interesting theoretical and empirical support. Regarding theory, in (at least some) non-human species, climate is associated with between population variation in cognition, brain size, and heritable neural functioning (see, for example: Roth et al., 2010; Roth et al., 2012; Roth et al., 2013); cold evolved populations are, apparently, sharper. For humans, models which assume a simple relationship between selection conditioned on cognitive ability and climatic harshness over the last 60,000 years reasonably predict current global cognitive capital (see: Hart, 2007; relatedly: Grall, 2012). Regarding empirical findings, climate by way of cranial size explains a non-trivial portion of the National IQ variance (see: Meisenberg and Woodley, 2013). Generally, cognitive and cognitively related somatic differences are in agreement with the cold weather model; this model is also in agreement with the literature regarding other species."[21]

The theory has been argued to be further supported by several studies which have found larger cranial cavity volumes in pre-human hominids who lived in colder climates compared to pre-human hominids who lived in warmer climates.[31]

New genetic mutations, which could include ones causing higher IQ, would be more likely to arise in large populations. This can be combined with the cold temperature theory. This would explain why Arctic People who live in very cold areas, but only as small populations, did not evolve a very high IQ. Europeans and East Asian who had large populations and lived in relatively cold areas evolved a higher IQ.[3]

J. Philippe Rushton in his book Race, Evolution and Behavior argued that the differential K theory explains many examined differences between human races including intelligence. The differential K theory also argues that different climate is an important evolutionary cause of the racial differences.

A 2016 study argued that genetics influence motivational factors related to the differential K theory rather than intelligence ability itself.[33]

Studies in several countries have found that IQ vary on a north–south gradient inside the countries as predicted by the climate theories.[34][35][36][37][38]

Another theory is that living in more evolutionary novel environments in general would have favored higher intelligence.[30]

For example the books The 10,000 Year Explosion and A Troublesome Inheritance: Genes, Race and Human History have argued that there may have been evolutionary changes also in recent human history caused by different selection pressures in different human societies.

One such proposed explanation is the imperial examination system in China and similar systems in other East Asian countries.[39]

Another is that in relatively recent European and East Asian societies three key elements are argued to have existed: 1. Class differences that reflect differences in intellectual performance. 2. A higher level of reproductive success in higher social classes than in lower ones. 3. No barriers to downward social mobility. The lower classes are argued to have been gradually replaced by people of higher social origin (and IQ). This is argued to have caused a relatively recent increase in IQ in these societies. Other societies are argued to have lacked stratification, or to have been too rigidly stratified, or to have favored other characteristics than IQ as causes of social mobility. There are also criticisms of the theory, such as regarding such societal elements argued to differ between different East Asian societies.[40][41][42]

Different castes and other groups in India have been argued to have different average IQ which has been argued to reflect different ancestral origins and/or recent different evolutionary pressures for different groups. See the article on India and the external links there.

Evolutionary theories have also been proposed for more narrow abilities such as the in regards the relatively high spatial abilities of Amerindians and East Asians. See Other race differences: Visual memory.

See also the articles on Jews and intelligence and Dysgenics regarding some factors that relatively recently may have affected some populations.

Race, sex, and intelligence

Some studies have found differences in average measured intelligence between the sexes with the results varying for different populations. A 2014 study stated that higher average intelligence in a population is associated with higher average intelligence differences between the sexes in the population. An evolutionary explanation for these and other population differences is that intelligence is a trait influenced by sexual selection.[43]

Interventions affecting IQ

Both hereditarians and non-hereditarians in principle agree on that measures should be implemented against certain environmental factors that are known to negatively affect IQ. Such factors include certain nutritional deficiencies (such as iodine deficiency) and certain diseases during pregnancy/childhood (such as malaria). Such factors are particularly prevalent in developing countries.

However, many non-hereditarians and advocates of political correctness tend to avoid mentioning (and may even actively censor mentioning) the measured average IQ differences and their importance, which may contribute to such interventions not being done or being done less forcefully.

Another problematic aspect (according to hereditarians) is that non-hereditarians (despite arguing that IQ differences are due to 100% environmental factors and an unjust society) have regarding the IQ differences in developed countries had difficulty in finding the societal interventions required to close the gaps or even had difficulty in finding interventions causing any lasting narrowing the gaps. See Race and intelligence: The genetics or not debate: Intervention programs.

Significance of IQ differences

Significance of IQ and g

The importance of IQ may be attacked which would make IQ differences unimportant. The America Psychological Association's report "Intelligence: Knowns and Unknowns" rejected this argument and stated that IQ predicts several important life outcomes and achievements. This is also why IQ tests and closely correlated tests are used widely in many educational and occupational settings.[14] Also, IQ has been argued to be the best single predictor of academic and job performance and attainment and one of the best predictors of a plethora of other outcomes. If predicting the life outcomes of a teenager based on only one fact about them, nothing is argued to be nearly as informative as their IQ.[44]

The g factor (general factor) is the underlying general mental ability that is measured more or less well by different cognitive tests The existence of g does not exclude the existence also of narrower cognitive abilities (that correlate with one another and g as explained in the IQ article). g has sometimes been criticized for reasons such as being a claimed statistical artifact. Supporters argue that such attempted criticisms have a long history but that all have ultimately failed. For example, there have been many unsuccessful attempts to find important forms of intelligence that do not correlate with g. Furthermore, g is argued to have a very high heritability, to be unchanged by training such as taking repeated IQ tests, to account for almost of all of the predictive ability of cognitive tests, and findings in neurobiology “establish a biological basis for g that is firmer than that of any other human psychological trait”. Furthermore, successfully discrediting g as a statistical artifact would change the situation much less than some may expect. Different races would continue to systematically differ on numerous different tests of various correlated cognitive abilities as well as to continue to systematically differ on various correlated life outcomes and achievements and there would still continue to be correlations between cognitive tests and life outcomes and achievements.[44][45]

Also the anti-hereditarian IQ researcher James Flynn has rejected attacking g in order to discredit racial IQ differences and has stated regarding Stephen Jay Gould’s book The Mismeasure of Man (which attacked the hereditarian Arthur Jensen) that "Gould’s book evades all of Jensen’s best arguments for a genetic component in the black-white IQ gap, by positing that they are dependent on the concept of g as a general intelligence factor. Therefore, Gould believes that if he can discredit g, no more need be said. This is manifestly false. Jensen’s arguments would bite no matter whether blacks suffered from a score deficit on one or 10 or 100 factors."[45]

Significance of environmentally caused IQ changes

Some opponents of a genetic explanation for IQ differences seem to think that if only the differences are due to environmental factors, then the differences are unimportant and can be dismissed. However, a lowered IQ due to, for example, iodine deficiency during childhood/pregnancy causing lifelong lowered IQ is important for individuals and societies despite the cause being completely environmental.

Very low average IQ values

IQ values such as the 54 for Bushmen (see the section "Worldwide") have been by some as implausible low since it would imply a diagnosis of mental retardation in European countries. However, besides this value being based on only three studies, Europeans with more severe forms of mental retardation often have genetic diseases that cause many other problems beside the low IQ. A better comparison is with European children with comparable IQ. An IQ of 54 is equivalent to the average IQ of European 8 years old children. These can learn to read, write, and do arithmetic. Historically the great majority European children worked productively at this age. This is also the case today for many children of this age in developing nations.[3]

Personality and apparent IQ

Some low average IQ groups on average also have been argued to have an extrovert, self-assured, talkative personality (possibly related to the Differential K theory) which may cause some people to overestimate the average IQ of such groups and to be reluctant to accept as valid the results from IQ testing.[46]

Historical societies

The book Understanding human history: An analysis including the effects of geography and differential evolution as one theme argued for differences in average intelligence between human races as a major factor in the course of human history and prehistory.[47]

Differences regarding average IQ is one explanation for differences between different regions regarding early achievements such as the creation of civilizations. However, non-hereditarians have pointed out that the earliest civilizations often occurred in regions which today do not have a very high average IQ. One response is that hereditarians have never argued that IQ (or genetics) is the only explanation for differences between human groups. The earliest civilizations occurred in very fertile river valleys which at the early stages of technological development likely were the only regions which allowed the high population density necessary for the development of civilization. In contrast, factors such as the long, harsh winters and the very hard clay soils in Northern Europe for a long time prevented a high population density. Technology had to advance greatly before this changed, one example being that the technologically much more advanced heavy plough necessary to take advantage of such clay soils was first introduced in the Medieval period.[48][3]

Another argument is that the average IQ of the populations creating the first civilizations may have been very different from the average IQ of the populations now inhabiting these areas. These areas have often seen extensive invasions and immigrations and it has even been argued that many of the first civilizations were created by groups completely different from the groups now living in the corresponding areas. Even if not, the average IQ may have been substantially changed by factors such as interbreeding with slaves from low IQ groups, dysgenic practices such as high IQ persons having fewer children, or dysgenic effects caused by society/religion not rewarding intellectual curiosity.[49][3]

Another factor is that the ruling/cognitive elite in the early civilizations may have been from a very different racial group than the rest of the population. Conquering peoples have often formed a ruling elite racially different from the rest of the population and many of the more cognitively demanding tasks have in many societies been performed by foreigners or minority group(s) racially different from the rest of the population.

A well-documented example of such an elite were the small minorities of Greeks/Romans in Egypt during the Ptolemaic dynasty/Roman empire who ruled the country and who made many important scientific and mathematical contributions (for example, Euclidean geometry). Another example is the so called "slave soldiers" in many Islamic empires who were often from high IQ groups such as East Asians ("Turks") or Europeans and who despite the name often were the top administrators or even the rulers of the empires. The Janissaries and the Mamluks are well-known examples but "slave soldiers" dominated the army and the government already during the Abbasid dynasty (the "Islamic Golden Age") and similar groups played important parts in the Islamic expansion before this.[50]

Morphological evidence based on for example statues, paintings, skeletal remains, or mummies have often been used to argue that various ancient populations or cognitive elites were quite racially different from the current populations living in the same area. Even if historical records are available, practices such as religious conversion are often accompanied by changing personal and family names which often makes it difficult to identify the correct race from the name of persons. The earlier presence of racially different cognitive elites or internal dysgenic changes in a population may be difficult to detect by genetic studies of the current populations living in these areas.

See also the article on the Ancient Egyptian race controversy.

More generally, dysgenic changes including regarding IQ have been suggested to be an important explanation for the fall of various civilizations. The book Why Civilizations Self-Destruct is one often mentioned example of such arguments.[51]

Mesoamerica (before the Age of Discovery) has been argued to have had more favorable environmental factors than sub-Saharan Africa (such as sub-Saharan Africa having had contacts with the regions to the north and their technologies and useful flora/fauna) but Mesoamerica is argued to despite this to have been a more advanced region (one example being the Maya who lived in a jungle region). This has been argued to be explained by average intelligence differences.[52][47]

Race differences in intelligence can explain why most conquests of people(s) by another people throughout human history have involved a northern people conquering southern people(s). This despite the northern regions being usually less populous due to harsher climates. For example, China was never threatened by southerners but repeatedly conquered by northerners. Similarly, India was repeatedly conquered by northerners. Europeans conquering various southern peoples but not East Asians, etc.[53]

Regarding the race of the known scientists/inventors, the overwhelming majority are Europeans. See Human Accomplishment: The Pursuit of Excellence in the Arts and Sciences, 800 B.C. to 1950.

Lynn has argued that East Asians, despite having slightly higher average IQ, have produced much less creative discoveries and innovations in the arts and sciences than Europeans. One possible 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.[54]

Modern societies

For various associations between average measured IQ and life outcomes for individuals and groups see:

Countries and intelligence: Associations with other variables
The Bell Curve: Tables
Intelligence quotient: Real-life accomplishments
Intelligence quotient: Social outcomes
Smart fraction

A significant part of the debate following The Bell Curve was regarding how important the IQ group differences were for the future achievements of the groups in the US. The book argued for the strong importance of IQ for numerous factors such as future educational achievements, employment, income, divorce rates, and crime. See the links above regarding tables from the book on this.

A 2016 analysis of US data found a substantially larger effect of IQ on permanent income than some previous investigations.[55]

Furthermore, a high IQ has been argued to be more important for group outcome differences than for individual outcome differences. A 2011 study presented "four different channels through which intelligence may matter more for nations than for individuals: (i) intelligence is associated with patience and hence higher savings rates; (ii) intelligence causes cooperation; (iii) higher group intelligence opens the door to using fragile, high-value production technologies; and (iv) intelligence is associated with supporting market-oriented policies."[56]

A 2013 study found that the ability of tests to measures the g factor was higher in low scoring countries than in high scoring countries, implying that the predictive ability of tests may actually be higher for low average IQ countries than for high average IQ countries (where most studies of predicative ability have been done).[57]

The book Guns, Germs, and Steel by Jewish biologist Jared Diamond, written as one response to the Bell Curve, argued that geographical differences caused differences in available resources which caused some groups to get a head start which explains today's differences in achievement between different parts of the world. One problem with Diamond's book is that it contains no actual arguments against the IQ explanation but simply describes an alternative explanation regarding worldwide developments. He also states that the populations in question separated a long time ago and that they faced different environments thereafter. These facts have been argued to virtually guarantee that the populations diverged genetically. Rushton notes, "It seems incredible that, as an evolutionary biologist, Diamond seems unaware that it is different environments that cause, via natural selection, biological differences among populations."[58] Furthermore, hereditarians have not denied that geographic and other non-IQ factors may be important. For example, IQ and the Wealth of Nations argued that average IQ, natural resources such as oil, and the presence or not of Communist economic systems have been major determinants of economic growth after WWII. Also, Diamond's argument does not explain why the different races in the same country achieve differently. See also the article on the book.

Lynn in the 2008 book The Global Bell Curve, named after The Bell Curve, argued that the same racial hierarchies exist in all countries that have several races with the different races differing similarly regardless of country regarding variables such as crime, income, school results, education, etc. It does not matter if some groups were very poor when they arrived to a new country. After a while the same consistent racial hierarchies as elsewhere are established. Furthermore, mixed-race groups almost always place intermediate between their two ancestral races on such variables. A group that is particularly difficult to explain using political correctness is East Asians in Latin America and other areas and who often arrived very poor in order to work as plantation workers and in similar occupations but now usually have a high socioeconomic status despite never having any political power or receiving any preferential treatment.

There are also some countries that are racially different from the surrounding countries and that perform very differently from these surrounding countries on various variables. Examples include Haiti (predominantly Sub-Saharan Africans) and Singapore (predominantly East Asians).

One explanation for such group differences are different "cultural values". This is however also a politically problematic explanation since it implies that all cultures are not equal. Hereditarians have criticized such explanations as being very difficult to test and likely also partially genetically influenced. See Other race differences: Values and Other race differences: Personality traits. There are also general arguments against such environmental factors, at least in developed countries, see Race and intelligence: The genetics or not debate: Shared environmental factors and Race and intelligence: The genetics or not debate: Environmental factors specific to only one (or some) race(s).

"From a more historical perspective, based on an analysis of 123 countries, 54 of which were European colonies, Prayon and Baten (2010) found a European colonial migrant human capital effect. European migrants to Africa, South Asia, Oceania, and the Americas had to begin with higher levels of developed cognitive ability (as indexed by age heaping) than the peoples indigenous to those regions. The authors found that the contemporaneous benefits of the historic human capital infusion, resulting from European migration to these areas, varied as a function of the ratio of European migrants to non-European natives. The implication is that historic European migrants brought their region of origin abilities with them and that this historic migrant effect persists still today. As one might expect from the above discussion, genomic racial ancestry, which varies extensively in the Americas due to historic migrant waves, predicts cognitive and/or cognitive related outcomes across the Americas, between nations, between regions within nations, and between individuals within national ethnic groups (Fuerst and Kirkegaard, 2015)."[21]


Several IQ researchers have expressed very pessimistic views regarding the future of Western civilization due to mass immigration of low-IQ groups and other dysgenic trends. See Dysgenics: Pessimism regarding the future of Western civilization.

External links

Article archives


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