Race Differences in Intelligence

Do races differ in intelligence? Is it all environmental or is there a genetic cause?

The connection between race and intelligence has long been debated. With some denying it right out, accepting it, or complicating simple stuff in order to say that there is no connection. The topic at hand isn’t very complex, and in a matter of moments you can understand it. Race differences in intelligence, as a matter of nature, have no moral standing, thus they can not be racist. In order for something to be racist, it must be bad. And since race differences have no moral standing, they aren’t racist or bad. Reality may frustrate our wishes, but sensitive topics can’t be thrown away because they may hurt someone.

Before we actually get into race differences, there are some stuff people need to know before we delve in any further.

Some Small, Important Stuff

Before we begin, there are a few things one must understand before reading further.

  • SD: Standard Deviation is a statistical measure used as a measurement for a group and how it’s spread out from the average, or from another groups average. 1 SD= 15 points; 2 SD= 30 points
  • A Bell Curve: A bell curve tells us the distribution of values, probabilities of a set of data or frequencies. The middle of the bell curve is called a mean, and from there the bell curve slopes downward. To lean more, click here.
  • Hereditarian: Someone who believes that genes influences a persons intelligence, behavior, and other traits that could differ by race. They don’t deny environmental influences
  • Environmentalist: Someone who believes that only the environment influences a persons intelligence, behavior, and other traits that could differ by race
  • Null-hypothesis:A general/ default statement that there is no difference between populations, and if there is, it’s probably due to errors.

Now that that’s out of the way, we can dig into the more technical stuff, and then counter-arguments people have made and other overall race differences in IQ.

The g -Factor

The factor, also known as general intelligence, was proposed by Charles Spearman in the area of psychometrics. It is a variable that correlates among st different cognitive tasks.


Spearman proposed that IQ correlations all went to an underlying variable he called g. According to Spearman, all these people who did well on one test did well on other test, so the factor was proposed. To extract g, people performed a technique called factor analysis. To quote Gottfredson:

“analysis determines the minimum number of underlying dimensions necessary to explain a pattern of correlations among measurements. A general factor suffusing all tests is not, as is sometimes argued, a necessary outcome of factor analysis. No general factor has been found in the analysis of personality tests, for example; instead the method usually yields at least five dimensions (neuroticism, extroversion, conscientiousness, agreeableness and openness to ideas), each relating to different subsets of tests. But, as Spearman observed, a general factor does emerge from analysis of mental ability tests, and leading psychologists, such as Arthur R. Jensen of the University of California at Berkeley and John B. Carroll of the University of North Carolina at Chapel Hill, have confirmed his findings in the decades since. Partly because of this research, most intelligence experts now use g as the working definition of intelligence.”

The existence of as a statistical regularity isn’t denied (some do deny it, but that’ll be taken up soon), and it’s recognized that a general cognitive factor appears in data from every human culture (Warne and Burningham 2018). Some people have tried to deny the reality of g, by claiming that it’s only a statistical artifact (Gould 1996), especially Hampshire et al. (2012) which claim:

The results disprove once and for all the idea that a single measure of intelligence, such as IQ, is enough to capture all of the differences in cognitive ability that we see between people,”

“Instead, several different circuits contribute to intelligence, each with its own unique capacity. A person may well be good in one of these areas, but they are just as likely to be bad in the other two” (Connor 2012).

In their paper, they also cite Gould (a popular egalitarian, race denialist) many times:

It remains unclear, however, whether population differences in intelligence test scores are driven by heritable factors or by other correlated demographic variables such as socioeconomic status, education level, and motivation” (Gould, 1981).

More relevantly, it is questionable whether they relate to a unitary intelligence factor, as opposed to a bias in testing paradigms toward particular components of a more complex intelligence construct” (Gould, 1981).

So, what’s the problem with citing Gould ? Well, Gould is a fraud. He lied about many things in his book. For example, in The Mismeasure of Man (mind you, the revised edition), Gould claims that g is just an artifact and ignored countless other studies that proved him wrong. Levin (1997) does proper justice at refuting Gould, but I suggest to only read him if you have a high level understanding of statistics and psychometrics. Regardless, other studies have proved Gould stance on wrong (Carroll 1995Hunt 1995Jensen and Weng 1994).

Not only this, but Hampshire et al. have also been responded to Haier et al. (2014); their response highlights key issues against this study. To quote the paper:

The authors issued a press release from their university (The University of Western Ontario in Canada) the day before the Neuron publication on December 20th. This press release is in Appendix C. The title is: “Western University-led research debunks the IQ myth.” The press release received some attention mostly in non-science media outlets and hyped the study as demonstrating definitively that IQ was a meaningless concept. For example, the senior author, Adrian Owen, was quoted as saying: “When we looked at the data, the bottom line is the whole concept of IQ — or of you having a higher IQ than me — is a myth… There is no such thing as a single measure of IQ or a measure of general intelligence.” Of course, most psychologists understand that this is a classic “straw man” argument since no one claims that an IQ score (which is a composite of a test battery) measures the whole of human intelligence. It is also widely understood that the g-factor is not synonymous with IQ.”


The study’s design appears to have suffered from a conceptual confusion that sometimes appears in studies using factor analysis. Hampshire et al. used averaged voxel activations (in a limited set of brain areas) across all 12 tests and all 16 subjects as the basis for identifying the two brain networks but then related these average across-subject voxel activation differences to individual differences in task performance in the much larger internet sample. The interpretation of these associations as indicating that neurological factors underlie variation in task performance is questionable.

What does this mean? Well, it probably says, “Hampshire et al., you guys are full of shit and jump to conclusions based on methodological flaws by doing an online IQ test on THOUSANDS of people and fMRI scans on only 16 people of which you used to make a large blanket conclusion,” but that’s just me – I don’t wanna put words in their mouths. Anyways, Spearman’s hypothesis on has been replicated many times (Jensen 1998), and if you wanna a better take down of g-denialism, I suggest to click here.

It’s important to note that the races differ in g, general cognitive ability. This is important to understand as we continue, especially for the Flynn Effect.

What is Intelligence?

A common tactic by egalitarians, race-IQ-deniers and others is to first ask “What is Intelligence?” While, at least to me, this seems like a stalling tactic – it is a good question that should be answered.

Rindermann, Becker, and Coyle (2016) note that

Cognitive ability is understood as the ability to think (intelligence), the disposition of knowledge (the store of true and relevant knowledge), and the intelligent use of this knowledge.

Plomin and Stumm (2018) note intelligence as

“the ability to learn, reason and solve problems

Neisser et al. (1996) found that both laymen and researchers regard intelligence as efforts to organize a complex set of phenomena, including the

ability to understand complex ideas, to adapt effectively to the environment, to learn from experience, to engage in various forms of reasoning, to overcome obstacles by taking thought.”

The most comprehensive data on what defines intelligence, that I could find, comes from Legg and Hutter (2007). They looked at definitions of intelligence from organizations, psychologists, and AI researchers. While they do say that there is no uniform agreement on what intelligence means, the definitions they got could all be summed up as

Intelligence measures an agent’s ability to achieve goals in a wide range of environments.”

Baker (1974) also uses intelligence to mean the abillity to solve problems and understand concepts.

So from this point on, intelligence would be taken to mean the ability to solve problems and understand concepts. I ask the reader: Think of a 2 people of whom you know. Which one is intelligent and which one is less intelligent than the other? Why is this so? I assume that even the reader can see that one friend has a faster time understanding and solving stuff, while the other friend takes longer.

“Intelligence means different things in different cultures”

Another argument usually taken up is that “intelligence means different things in different cultures” (Sternberg 2004Sternberg and Grigorenko 2004; Benson 2003). What this argument tries to do, much like the theory of multiple intelligence, is to stretch out what the word “intelligence” means. Instead, they lump in things like athletic skill and say: “Africans see intelligence as being good in sports.” In fact, Sternberg even tries to make the case that someones talent may not be reflected on academic test. Because someone may have social skills or can fish, this doesn’t tell us anything about their intelligence. This line of reasoning is just an ad-hoc, it to tries to lump talents, skills and other things to try to invalidate what intelligence is (Levin 1997).

The Theory of Multiple Intelligence

Much like the argument taken up above, the theory of multiple intelligence also tries to expand the word intelligence to fit things like talents and skills. The proponent of multiple IQ theory, Gardner and others, claim that IQ could be broken down into multiple things: musical, visual, verbal, logical, bodily-kinesthetic, interpersonal and intrapersonal (self-reflective).

The first thing that should be obvious is how musical talent is taken to be a type of intelligence of its own, rather than just that – a talent. There are problems proving Gardner’s theory in the first place as he’s opposed to psychometric testing. Waterhouse (2010) found no support for the theory of multiple intelligence. Again, all this tries to do is stretch out the word intelligence to fit stuff that it doesn’t even align with. Talents =/= intelligence.

Now that we’ve gotten through that, we can move onto the meat of what you’re probably here for: race differences in IQ.

Race Differences: IQ Test Data

For the sake of simplicity, IQ differences will be talked about for whites, blacks and Asians (for a full review on race differences in IQ between and within groups, refer to Lynn 2011). Herrenstein and Murray (1994) introduced the general population to race differences in IQ: The general evidence shows:


As can been seen, there’s a 1 SD (15-point) gap between blacks and whites. Rushton and Jensen (2005) note:

Currently, the 1.1 standard deviation difference in average IQ between Blacks and Whites in the United States is not in itself a matter of empirical dispute. A meta-analytic review by Roth, Bevier, Bobko, Switzer, and Tyler (2001) showed it also holds for college and university application tests such as the Scholastic Aptitude Test and the Graduate Record Examination, as well as for tests for job applicants in corporate settings and in the military.

The findings for race differences in intelligence have been found in Rushton and Jensen (2010)Rushton and Rushton (2001)Lynn (2011), and Lynn (2008). For blacks and whites specifically, the race differences in IQ have been replicated a lot (Levin 1997; Pesta and Poznanski 2008). Race differences in IQ have been present for the past 10,000 years (Lynn 2009), and race differences in IQ could also been seen between races in children as young as 3 (Peoples, Fagin, and Drotar 1995).

When 600 researchers and educators were polled anonymously about race and IQ (Rothman and Synderman 1988):

  • 84% agreed that intelligence test do measure intelligence, as either a single general ability or a cluster of more specialized  abilities
  • 53% agreed that genes contribute to race differences in IQ
  • Only 17% saw it as purely environmental

In fact, a more recent survey from Rindermann, Becker, and Coyle (2016)found:

Question: 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%

While this poll is talking about IQ and genetics between blacks and whites, researchers at least do seem to acknowledge that there are race differences in IQ.

Thus, we know that the average black is less intelligent than the average white and Asian. When someone says this, the first response is that of individualism. This line of thinking ignores how individuals make a population. Why are there certain stereotypes about certain races? It’s because individuals make up those stereotypes – and they’re true.

Environmental Factors

The environmentalist position dictates that while there maybe race differences in intelligence, it’s because of the environment rather than genes – and if genes do play a role, it’s very small. First, if you didn’t sort through the data and examine how well the environment affects IQ – then don’t claim that its more environmental than genetic. It’s easy to claim that low SES, for example, lowers IQ than to actual read through the papers and see if they hold true across racial lines. Second, it’s easier to make null-hypothesis about what could affects IQ rather than what does.

Culture-Bias in IQ Test

Some people say that IQ test are culturally biased against some minorities (Bensen 2003), but this isn’t the case (if it were, why do Asians score higher on IQ test)?

Reeve and Charles (2008) found that 73.3% of experts surveyed said that there is no cultural-bias in IQ test.

The National Research Council and The National Academy of Scienceconcluded that cultural bias explained nothing in race differences in IQ.

Gottfredson (1994) noted that IQ test aren’t biased against blacks.

Neisser at al. (1996) found that IQ test aren’t “biased against African Americans.”

From my experience, some people cite some fringe researchers thinking IQ test are biased, but the evidence doesn’t suggest that. Some people also think the earth is flat, but that doesn’t matter.

Socio-Economic Status:

The evidence does suggest that smarter people come from higher SES homes. Sirin (2005) meta-analyzed data on roughly 1000,000 students and found that the correlation between IQ and SES is .26. Which is weak to moderate for r. The problem is that SES is also heritable at .42% (Hyytinen et al. 2013). Regardless, controlling for SES will be taken up later.

Twin studies have shown that poor kids put into higher SES had their IQ raised by x points. Schiff et al. (1978) found that poor french children put into higher SES homes had their IQ raised by 15.5 points. Scarr and Weinberg (1983) found that the IQ of kids put into higher SES homes also increased. It does seem like socio-economic status can explain the black-white IQ gap, but this isn’t so.

While I’m not aware of any follow-up study done on Schiff et al., there was one done on Scarr and Weinberg. The IQ of the adopted sibling put into a higher SES actually regressed back to near their original IQ (Levin 1997). So studies that find an increase in IQ are finding gains, but these aren’t permanent. The gains end up dropping later in life.

Scarr, one of the researchers, did a follow up and she said that education is important in raising IQ, but it seems that she reported on her findings with a stake in race-IQ debate:

“The test performance of the Black/Black adoptees [in the study] was not different from that of ordinary Black children reared by their own families in the same area of the country. My colleagues and I reported the data accurately and as fully as possible, and then tried to make the results palatable to environmentally committed colleagues. In retrospect, this was a mistake. The results of the transracial adoption study can be used to support either a genetic difference hypothesis or an environmental difference one (because the children have visible African ancestry). We should have been agnostic on the conclusions”

To the degree that SES impacts IQ for both blacks and whites isn’t what some may think it is. A 9-12 point gap remains when status is controlled for (Jensen 1980; Neisser et al. 1996); white children have higher Peabody Vocabulary Test scores at all income levels (Currie and Thomas 1995); lower class whites consistently do as well or better than middle and upper class blacks (Jensen 1980; Scarr 1981). Herrenstein and Murray (1994) found that as Black  IQ scores go up with SES, it doesn’t close the black-white IQ gap.


So what if studies controlled for SES like Jensen did? Shuey (1966)looked at 42 studies carried out between 1913-1966 in which blacks and whites had the same SES. 95% found that whites still had higher IQ’s; 2 found no race differences when SES was controlled for, but none found that blacks were smarter than whites.


Multi-vitamins do affect IQ, but it seems to be for small stuff – not g(general intelligence [Grima et al. 2012]). It’s hard to make the argument that blacks have worse nutritional habits given their overall athletic preformance, and given the fact that surveys shows that blacks consume more fruitsvegetablesmeat and sugar than do whites in the US, and also have a higher obesity rate.

Statista (2017)

Stereotype Threat and Motivation:

Stereotype threat refers to situations in which people might feel at risk to confirming to their groups stereotype, and then this causes them to do bad on test.

Wei (2009) looked at 64 papers on race and gender stereotype threat, and stereotype threat was replicated only 58.4% of the time. This shows replication bias, and it was only produced almost 60% of the time, and 30% of the time it wasn’t. To quote an article looking at the replication of stereotype threat:

In conclusion, a replicability analysis with the R-Index shows that stereotype-threat is an elusive phenomenon. Even large replication studies with hundreds of participants were unable to provide evidence for an effect that appeared to be a robust effect in the original article. The R-Index of the meta-analysis by Flore and Wicherts corroborates concerns that the importance of stereotype-threat as an explanation for gender differences in math performance has been exaggerated. Similarly, Ganley, Mingle, Ryan, Ryan, and Vasilyeva (2013) found no evidence for stereotype threat effects in studies with 931 students and suggested that “these results raise the possibility that stereotype threat may not be the cause of gender differences in mathematics performance prior to college.” (p 1995).

Pennington et al. (2019) found that stereotype threat didn’t harm student performance, further leading to the argument that this isn’t a problem in IQ test.

You can read more of this type of “voodoo” science here. It also makes no sense to think that this would replicate in the real world as researchers aren’t telling minorities that their population does bad on test in the first place. They take the test, and get their results. No “your people are idiots” here.

Another argument taken up is that race differences in IQ test are caused by motivation (refer to Nauret 2018). First of all, in general there are race differences in motivation. Mau and Lynn (1998) looked at standardized scores math, reading and science, and number of hours devoted to working on homework per week.

It is suggested that motivational differences expressed in the amount of homework undertaken contribute to the group differences in educational achievement. Statistically significant correlations between the amount of homework and educational achievement support this hypothesis. There are also group differences in intelligence parallel to those in educational achievement, suggesting both intelligence and motivation are involved in racial and ethnic differences in educational achievement.”

Motivation does affect IQ, but if motivation differs by race – what exactly are you gonna due to change that? If we use academic achievement as a proxy for motivation and control for IQ, we find that cognitive ability is a better predictor of academic achievement that motivation, and that students’ “self-assessments of their motivation were not related to their academic achievement” (Gagne and Pere 2002).

Child Abuse:


Overall, there are race differences in child abuse. Twin studies also find that child abuse makes you less intelligent compared to someone who wasn’t abused (Koenen et al. 2003). This can’t be a result of white racism or historical oppression, but that something that, sadly, does happen.

The Flynn-Effect:

Supposedly, IQ has been raising for all races – which should mean that there is no IQ gap anymore. What the Flynn-Effect measures is things unrelated to g. So it’s telling us NOTHING about how races differ in general intelligence. As Rushton and Jensen (2005) said:

One culture-only hypothesis currently enjoying much support is based on the secular increase in test scores, known as the Flynn effect because of the repeated demonstration by James Flynn (1984, 1987, 1999) that the average IQ in several countries has increased by about 3 points a decade over the last 50 years. Some have suggested that the Flynn effect implies that the 1 standard deviation difference in the mean Black–White IQ difference in the United States will gradually disappear over time (Flynn, 1999). However, one statistical analysis shows that the Flynn effect is not on the g factor, the principal source of the mean Black–White group difference.

Nijenhuis and Flier (2012) found a negative correlation between score gains and g-loading, and that the Flynn Effect and group differences have different causes.

Biological Factors:

Heritability of IQ:

It’s important to note what heritability actually is. As the Rushton and Jensen paper cited on the top also notes:

“Heritability refers to the genetic contribution to the individual differences (variance) in a particular group, not to the phenotype of a single individual. Heritability is not a constant that holds for all groups or in all environments. A heritability of 1.00 means all the observed differences in that group are due to genetic differences and not at all to their differences in the environment. A heritability of zero (0.00) means the converse. A heritability of 0.50 means the observed variation is equally the result of genetic and of environmental differences. The heritability of height in modern industrial populations, for example, is about 90%, which means that most of the differences in height among the individuals are due to their genetic differences.”

Saying this, the heritability of IQ increases with age. So as you get older, your genes start to play more a role than your environment. Most sources usually stop the heritability estimate at a young age to where it’s .5, but studies done until adulthood find a much higher estimate. Panizzon et al. (2014) found that the heritability of IQ is .86, and Pederson et al. (1996) find it at .8 (80).

Race and the Brain:

IQ and head-size:


As can be seen, there are race differences in brain size. IQ also correlates with brain size (not at .1, but a good, meaningful correlation).

Race differences in brain size can also be seen since the age of 3 among st different racial groups (Kirkegaard 2018).

A common objection to race differences in brain size is from Boas (1912), the founder of American Anthropology. He looked at European immigrant children and their parents – he found that the brain size of kids matched, not their parents, but non-immigrant kids. It turns on that Boas didn’t even control for brain size differences with the function of age. Sparks and Jantz (2002) re-looked at Boas’s findings and controlled for the age difference between the kids and their parents. The brain size of the parents and their kids didn’t differ – the statistical findings were negligible.  The brain size of the immigrant kids and non-immigrant kids also did differ. The most updated anthropology book I own still cites Boas as a big attacked against race being a valid biological concept.

The heritability of brain size is also .82 (Pepper et al. 2007).

Three meta-analysis on over 100 studies have found that people with bigger brains are more likely to score higher on IQ test (McDaniel 2005; Rushton and Ankey 2009;  Pietschnig et al 2015). They produced correlations ranging from  .24 to .40. McDaniel (2005) found a correlation of .21 – .41 in his meta-analysis for brain size and IQ. Using MRI scans on brain size and IQ on college students after body size was controlled for, Willerman et al. (1991) found an r of .35 between brain size and IQ when body size is controlled for. Andreason et al. (1993) obtained r’s from .26 to .56 between IQ and the size of  specific brain structures, and an r of .38 between IQ and full-scale IQ and grey matter volume. Raz et al. (1993)and Wickett, Vernon, and Lee (1996) got replications ranging from .41, .47 – .49. Overall, the data does suggest a significant correlation ( .21 <r< .56).

Andreason et al. (1993)  suggest that the remainder of variance is due to

aspects of brain structures that reflect quality rather than quantity of brain tissue: complexity of circuitry, dendritic expansion, number of synapses [or neurotransmitter] efficiency.”

Rushton (1988; 1997) looked at brain neurons (in millions of excess neurons) by race, and found that blacks have less brain neurons than whites and Asians. On average:

  • Blacks averaged 8,550 neurons
  • Whites averaged 8,660 neurons
  • Asians averaged 8,900 neurons

This difference in 100-200 million neurons would be enough to show racial differences in achievements.

The races are also NOT equal in genes associated with brain development. Genes associated with brain development differ at a higher frequency than those that control for skin color (Wu and Zhang 2011):

“Other genes that showed higher levels of population differentiation include those involved in pigmentation, spermatid, nervous system and organ development, and some metabolic pathways, but few involved with the immune system.”

IQ And Genetics:

Piffer (2015) looked at IQ related genes and found that they differ by race. Blacks have a higher frequency of low IQ related genes, and whites and Asians had a higher frequency of high IQ related genes:


It’s very fancy now for publications like Vox (2017a2017b) and The Guardian to say that race differences in IQ between racial groups are unlikely – or if they are – they aren’t genetic. The former has been found to be guilty of cherry picking (Noam 2017), they also misrepresent Charles Murray throughout the entire article (Sailor 2017) and use one of the authors studies (Turkheimer) that has failed replication more than 3 times (Nagoshi and Johnson 2004Asbury, Wachs, and Plomin 2005Bates, Hansell, Martin, and Wright 2016McGue 2013).

As for the Guardian article, they too are wrong (Jonatan 2018Last 2018).

3 thoughts on “Race Differences in Intelligence

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