There is an idea spreading on the internet that there are large racial IQ gaps- in particular the gap between white and black IQs- and that these gaps are predominantly due to genetic differences. Unfortunately, this idea has found many audiences on reddit, and there have been posts on this subreddit supporting that stance. Many of the people who advocate for race realism appear well-read and quote studies that seem to support their viewpoint. However, I believe that this ideology is not only extremely dangerous, but is also factually wrong. So, I will be devoting this post to bringing a wide range of evidence to disproving race realism.
First, I want to clarify a few of my positions before beginning my critique:
I believe that the IQ test is a reliable and unbiased measure of a significant part of what most people define as intelligence in industrialized societies. While the test has a sordid history of racism and misuse, the most-used IQ tests (eg: the WISC and WAIS) have gone through great lengths in reducing cultural biases in its questions.
There is no doubt that there is a racial gap in IQ: what I will be arguing is that this is primarily due to environmental- not genetic causes.
Finally, I believe that- like with most things- intelligence is a product of both inherited traits and the environment. In this post, I will be arguing that genetic differences are not the predominant explaining factor for the racial intelligence gap.
With my starting stances out of the way, let us begin:
A. Evidence from Racial Admixture studies
We benefit from having an African American population in the United States with a wide range of mixed European ancestry. This means we can have a powerful test of the hereditarian hypothesis. If the hereditarian hypothesis accurately explains the difference in Black-White IQ, then African Americans with greater European ancestry should have higher IQs then African Americans with less European ancestry. So, what does the data show?
I will first present a study which recruited black twins from 181 different families in Philadelphia. Using blood group markers, the researchers were able to estimated the percent Caucasian ancestry of the kids before having them take a variety of intelligence tests. They found that there was absolutely no correlation between white ancestry and intelligence. [1]
A separate study used skin color as an estimate of Caucasian ancestry and looked at 437 African American participants’ performance on a 10-point vocabulary test. The study found no correlation between skin tone and test performance when controlled for family and childhood educational background [2].
At the risk of beating a dead horse, I will look at one last racial admixture study to cement my point. In this study, researchers looked at black, mixed, and white kids adopted by either black or white middle class families. Mixed was defined as the child having one black and one white parent. The researchers (again) found no difference between black and mixed-race children in IQ as measured by WISC. However, even more interesting is that kids adopted to white families had significantly higher IQ scores than kids adopted to black families, suggesting a large environmental factor in producing differences in IQ. [3]
In order for the race realist argument to hold water, then there must be strong evidence that those who have greater European ancestry have a higher iq than those with less European ancestry. However, the various studies I have shown all disprove that argument.
B. Evidence from Twin Adoption Studies
This section will be structured more as a rebuttal than a point on its own, since race realists tend to rely heavily on twin adoption studies. The logic behind these studies run like this: monozygotic (identical) twins have the same genetic makeup, and adoption allows these twins to be placed in different environments. Therefore, the similarity in IQ between these twins who have been adopted into different households should be from a solely genetic origin. The logical throughline is strong, and race realists have used this experimental paradigm to arrive at IQ heritability values of around 0.85 or higher by adulthood.
This seems to be airtight, rigorous evidence for a high heritability of IQ. However, there is a large fault in a crucial assumption of twin studies: the assumption that the twins are adopted by families with very different backgrounds and live in very different environments. That assumption turns out to be false: Adoptive families tend to be more homogenous, with smaller variability of SES and HOME scores (used to measure the amount of intellectual stimulation present in a family environment). Indeed, a study that accounted for these variables found that the restricted variability of family environments in adoption studies could account for as much as 50% of the variance IQ found in these studies.[4]
C. Sub-Saharan IQ
Just as in part B, this section will be formatted as a rebuttal to a common argument of race realists: that the average Sub-Saharan IQ sits at a paltry 70. This IQ of 70 is the most commonly held number by the most prominent race realists such as Arthur Jensen and Richard Lynn [5]. One should be immediately skeptical of that number, seeing as that corresponds to a score a full two standard deviations below average. Put it another way, this would mean that the average person in Sub-Saharan Africa is less intelligent than 97% of people in America. So, what is the problem?
The problem lies with a variety of factors that all contribute to poor designs and biased results in the studies that race realists use to support their claim. The literature reviews tend to disregard relevant studies that show higher IQs, and the studies used tend to rely on convenience samples, which would not be relevant to the overall population. Finally, administering a western IQ test to a very different culture in developing nations poses many problems that make the tests less valid. Now, I have made broad attacks on the studies that race realists use without providing citations, and that is because there are several studies I would need to mention and this post is already extremely long. If anyone wants more specific information, I am more than happy to provide it in the comment section.
So, what is the best value we have for Sub-Saharan IQ? For that, I will rely on a systematic review of data on Sub-Saharan performance on Raven's Progressive Matrices. The inclusion criteria for this study was particularly rigorous, excluding any studies that did not adhere to administrative norms and found a value for IQ of...80, a full 10 points higher but still quite low when compared to that of industrialized nations [6]. However, there is still one factor to take into account: the Flynn Effect.
If the average Sub-Saharan African was compared to the average British person from 1948 you would find that their IQs would be identical [6]. As it turns out, There has been a steady increase in IQ over the 20th century in the industrialized world, a phenomenon called the Flynn Effect. Though the reasons are still unclear, the most common are improvements in children’s health, nutrition, and parental literacy, all of which agree with the limited correlational data we have [7]. Seeing as Sub-Saharan Africa is still the poorest region in the world, with poor food security and health infrastructure, it follows that we would see a corresponding Flynn Effect on African populations that mirrors that of the western world over the 20th century as Africa industrializes.
D. Modern Phrenology
Another core line of argument from race realists is the idea that brain volume correlates with intelligence. This argument is particularly enticing for two reasons: it presents a biological basis for heritable intelligence, and it has the intuitive reasoning that a larger brain means a smarter person. The issue is, as most people reading this can guess, the best data we have on the relationship between brain volume and intelligence is very minimal.
A meta-analysis of 88 studies on a combined >8000 individuals found that the relationship between brain volume and IQ has an R2 value of...0.06. Put it another way, brain volume explains 6% of the variation in IQ. That is an incredibly low number, and is completely inadequate as a biological basis for genetic causes of intelligence [8].
As a last line of evidence on this topic, I want to talk about sex differences in brain volume and IQ. We know that even when adjusted for height and weight, men tend to have a larger brain volume than women [9]. Therefore, if brain volume does correlate with intelligence, men should be more intelligent than women on average. However, the evidence for that is simply not there. Studies have argued men had lower IQs than women, women have higher IQs than men, and men having equal IQs to women. The best study that I can find, which looked at a nationally representative sample of UK kids and young adults, found no difference in IQ between men and women [10]. Again, the different lines of evidence just do not support the idea that larger brain volume means greater intelligence.
Concluding remarks:
The most popular lines of evidence race realists use to justify the hereditarian hypothesis (twin adoption studies, brain volume studies and cross-national IQ studies) all have deep methodological flaws or do not support their position. Moreover, racial admixture studies provide an extremely powerful contradiction to race realism: greater European ancestry in African Americans simply do not lead to greater IQs. I wrote this post not simply to critique race realism but to provide a wide variety of tools to argue against it, should you need them. I have seen first-hand how persuasive race realist arguments can be, and I think it is absolutely essential that more people should have the requisite knowledge to argue against an ideology that is sadly gaining ground.
I fully expect there to be race realists who will read this and critique it. I am more than willing to have a conversation with them, and I encourage everyone to avoid knee-jerk assertions of racism or personal insults.
References:
[1]Scarr, Sandra, et al. "Absence of a relationship between degree of White ancestry and intellectual skills within a Black population." Human genetics 39.1 (1977): 69-86.
[2] Hill, Mark E. "Skin color and intelligence in African Americans: A reanalysis of Lynn's data." Population and Environment 24.2 (2002): 209-214.
[3] Moore, Elsie G. "Family socialization and the IQ test performance of traditionally and transracially adopted Black children." Developmental psychology 22.3 (1986): 317.
[4] Stoolmiller, Mike. "Implications of the restricted range of family environments for estimates of heritability and nonshared environment in behavior–genetic adoption studies." Psychological bulletin 125.4 (1999): 392.
[5] Rushton, J. Philippe, and Arthur R. Jensen. "Race and IQ: A theory-based review of the research in Richard Nisbett's Intelligence and how to get it." The Open Psychology Journal (2010).
[6]Wicherts, Jelte M., et al. "Raven's test performance of sub-Saharan Africans: Average performance, psychometric properties, and the Flynn Effect." Learning and Individual Differences 20.3 (2010): 135-151.
[7] Daley, Tamara C., et al. “IQ on the Rise: The Flynn Effect in Rural Kenyan Children.” Psychological Science, vol. 14, no. 3, May 2003, pp. 215–219
[8] Pietschnig, Jakob, et al. "Meta-analysis of associations between human brain volume and intelligence differences: How strong are they and what do they mean?." Neuroscience & Biobehavioral Reviews 57 (2015): 411-432.
[9] Ruigrok, Amber NV, et al. "A meta-analysis of sex differences in human brain structure." Neuroscience & Biobehavioral Reviews 39 (2014): 34-50.
[10] Savage-McGlynn, Emily. "Sex differences in intelligence in younger and older participants of the Raven’s Standard Progressive Matrices Plus." Personality and Individual Differences 53.2 (2012): 137-141.
