It's unpersuasive, to say the least. Very young children (age 4), very small number of children with black mothers, and extremely noisy data. Glad well didn't imagine this study, but he certainly imagined its findings to be much more more robust and generalizable than they actually are.
Also, both mothers and fathers in the white female/black male couples were more educated than the black female/white male couples. And the latter actually had slightly higher incomes on average, ruling out poverty as an explanation for the gap.
Interesting. This study isn't mentioned in Flynn's article. It may be that Malcolm Gladwell was inserting his memory of this study into his memory of Flynn's presentation.
I've rewritten my post to discuss the findings of the Willerman et al. study.
Not on topic, but it would be interesting to hear your comments on this new paper providing genomic evidence for Gregory Clark's theory of the fundamental cause of the industrial revolution:
This is fascinating! I was expecting that Davide Piffer would repeat his earlier study with a larger sample of genomes, but this study has come earlier than expected. It provides a more detailed look at the increase in mean cognitive ability of the English population between 1000 and 1850.
Two preliminary observations:
- It looks like there was an acceleration and then a deceleration, with most of the increase occurring between 1400 and 1700.
- The increase in the "smart fraction" is impressive. The top 1% in 1850 was equal to the top 0.01% in the year 1000. This finding points to a considerable increase in the subpopulation of highly intelligent people above and beyond what would be expected from population growth alone. Intellectuals were no longer voices crying in the wilderness. They could now meet and socialize with other intellectuals. It was this potential for synergy that caused the Enlightenment and then the Industrial Revolution.
I am thinking that EA might not be the best estimate for what intellectual contributions one might expect from a population, though it obviously nevertheless correlates strongly. I remember that there was a strange discrepancy between the IQ and EA polygenic scores of Ancient Greeks in Evolutionary Trends of Polygenic Scores in European Populations From the Paleolithic to Modern Times. The Romans had higher EA polygenic scores, yet their intellectual contributions were mostly derivative of Greek innovations: verism from Hellenistic art, De Rerum Natura from Epicureanism, encyclopedic compilations based mostly on Greek thought (Pliny the Elder's Encyclopedia), etc. Roman contributions were mostly in (very good) fundamentals: for example, Cicero noted that the Roman Twelve Tables "surpass the libraries of all the philosophers, both in weight of authority and in plenitude of utility." Or consider this citation from a Greek observer: "The extraordinary greatness of the Roman Empire manifests itself above all in three things: the aqueducts, the paved roads, and the construction of the drains." Could these not be compared to the excellent idea of civil exams or what Francis Bacon called the "great inventions" ("printing, gunpowder, and the magnet") of Chinese civilization? There is even a quote parallel to that of Cicero: "... no empire, no sect, no star, seems to have exerted greater power and influence in human affairs than these three mechanical discoveries."
I suspect that verbal intelligence might be even more closely related to innovation than something like spatial intelligence, yet both would (I suppose) be measured as if they were equivalent by IQ polygenic scores. What I notice most from Greek civilization is an extreme capacity for meta-reflection and a unique tolerance for ambiguity, as can notably be seen in plays like the Oresteia and Antigone, or in the mere existence of people like Socrates and Aristotle. My guess is that La Griffe du Lion was onto something when he attributed an outsized influence to verbal IQ. There is a unique disposition to not simply wish to recompilate like Pliny the Elder (Roman) or Vincent de Beauvais (Medieval French) did.
A significant portion of EA polygenic scores may reflect non-cognitive factors, notably monotony avoidance and the ability to sit still in a classroom.
Can you tell me where in that paper the authors say that the Romans had higher EA polygenic scores than the Greeks?
If you check Figures S14 and S15 of the supplementary material, you can see that Iron Age Italy has the highest EA scores. The authors note, "The overall rankings were quite similar, with the lowest scores for hunter-gatherers, Neolithic Middle Easterners, and Copper Age Iberians, and the highest for Iron Age and medieval Italy (Supplementary Figures S14, S15, S16)." Figures S14 through S16 also show that the Bronze Age Greeks had middling EA scores but the highest IQ PGS. As the study states, "A significant divergence was noted in the sample of ancient Greeks from the Bronze Age in the comparison between IQ and EA. The Bronze Age Greeks, while displaying average scores on EA, manifested the highest scores in IQ PGS." Something else I’ve found interesting is that the decline in IQ PGS observed in Imperial Italy is not as dramatic as the decline in EA PGS.
To be fair, throughout this discussion I’ve been referring to the accomplishments of Classical Greece, whereas the study specifically measures the scores of Bronze Age Greeks. While there might have been some continuity in selection across periods, a dark age followed immediately after the Bronze Age, which suggests a potential cognitive decline. Moreover, it’s not clear which Bronze Age Greeks are represented. Minoans, Mycenaeans, or both? In my opinion, the Minoans were more impressive. Perhaps the Ancient Greeks followed a pattern similar to the Italian populations, with periods of high intelligence interrupted by one notable decline. The Greeks truly deserve a thorough, period-by-period analysis of their cognitive traits. I guess remains that don't show selection bias could be recovered from mass graves caused by massacres, plagues, or shipwrecks (they found one skeleton in the Antikythera wreck)?
Peter Frost’s What do you think of this blog post?This person tries to claim that the recent differences between whites and blacks and their outcomes is due to geography and other confounding factors like and starvation.
"Several white adopted children with low IQ scores were lost from the follow-up studies. The Black adopted children who were lost did not have unusually low IQs."
There were losses of participants in all four groups of children: 1) nonadopted, White biological parents; 2) adopted, two White biological parents; 3) adopted, one White and one Black biological parent; 4) adopted, two Black biological parents. Proportionately, the losses were about the same in all four groups
The children were measured for IQ at age 7 and again at age 17. The relative ranking of the four groups of children remained the same. If loss of participants "skewed" the data, it must have had exactly the same impact on each group.
------------------------ Age 7 Age 17
1) biological parents - 120 115
2) nonadopted, White - 117 109
3) adopted, White and White - 112 106
4) adopted, White and Black - 109 99
5) adopted, Black and Black - 97 89
All of the groups, including the adoptive parents, experienced a decline in IQ. There is some argument over whether this decline was due to renorming of the IQ tests or to a natural decline in learning ability with age.
As for the Flynn effect, some people think it is an intergenerational effect. If it is intergenerational, it wouldn't apply here, since we're dealing with the same generation. If it does apply here, the actual decline in IQ with age is even larger. So there are even fewer benefits from growing up in the enriched environment of middle-class Minnesota families.
Heritability of IQ Score
Yes, genetic differences become less important as environmental differences become more important. This is Logic 101. And this is why we should focus either on adoption studies or on direct measurement of the genetic component of IQ, i.e., alleles associated with IQ or educational attainment.
Is Heritability a Sensible Concept?
Again, Logic 101. If you increase environmental variability, hereditable variability becomes relatively less important. None of this invalidates heritability. It's like saying that the risk of death from smoking is nothing compared to being in Cambodia during the Khmer Rouge.
High Test Scores of Black British Immigrant Children
First, we're no longer talking about IQ tests. We're talking about the GCSE. Success on the GCSE is strongly influenced by coaching (and cheating).
Second, most Black British children do poorly on the GCSE. Unusual high rates of success are found among Nigerian students, especially Igbo. This success is due partly to coaching and partly to diligence in doing homework and attending classes. It may also have genetic causes.
Africa is a continent with a variety of populations, and IQ varies within Africa as it does within Europe. IQ seems to be higher in populations that have a longer history of trade and other forms of social complexity. This is notably the case with the Igbo, who acted as middlemen in trade between the coast and the interior via the Niger River. To some extent, it's true for other populations close to the Niger.
"blacks today aged 12 have a mean IQ of about 90.5; and young blacks have gained 5.52 points on whites over 30 years"
This is due largely to changes within the "Black" and "White" categories. A process of convergence is occurring through mass immigration. "Whites" increasingly include lower-performing groups, while "Blacks" increasingly include higher-performing groups, like Nigerian immigrants. Another factor is that biracial children have become proportionately more numerous, and they are usually categorized as "Black."
I won't discuss the issue of crime because it's influenced not only by cognitive ability but also by propensity for violence. In many traditional societies, violence is limited by a "balance of terror" — a murder will be avenged by the victim's male siblings and male cousins. Violence increases when this balance of terror is no longer operational.
This is the case in pacified societies where the State has long exercised a monopoly on the use of violence. A murder will not be avenged by the victim's male kin because that sort of vengeance has long been suppressed by the State.
The three reasons given by Rushton and Jensen for the disappearance of the black-white gap in the Eyferth study are not convincing. None of the factors they describe eliminates the gap significantly.
First point: "The African American soldiers in Germany were (...) a higher-IQ sample of the African American population."
My reply: Hardly true. Flynn's (1980, p. 84-94) detailed calculations in his "Race, IQ, and Jensen", which has received disappointingly little attention by hereditarians, show that blacks in the military should have had an IQ of 91.5, and even lower when taking into account regression to the mean and the imperfect correlation between the Army General Classification Test (AGCT) scores and Wechsler IQ. He estimated that regression to the mean would put it at 89.55 at most (narrow heritability of 0.7, so (91.5-85)×0.7+85=89.55). Then, the AGCT correlates 0.77 with the Wechsler among whites, but since the test contained questions related to school-taught knowledge and blacks had very few years of schooling at that time, and were arguably less motivated to take the test to serve in the military (e.g. some failed on purpose) (Flynn, 1980, p. 226), the correlation between the AGCT and Wechsler IQ for blacks could've been anywhere from .30 to .77 (p. 221), so this would further have lowered their IQ to 88.5 AT MOST.
Second point: "Between 20 and 25% of the 'black' fathers were, in fact, North African".
My reply: That doesn't make much a difference. North Africans seem to have an IQ around ~89 when raised in Europe, so let's assume that that's their genotypic mean IQ. Let's assume the North African soldiers constituted as much as 25% and had an IQ as high as 93 (adjusted for regression to the mean). Still, that would only raise the genotypic mean IQ of the "black" soldiers by 1.1 points – to 89.6. That's not much.
Third point: "The children were still young when tested. One third were between 5 and 10 years old and two thirds between 10 and 13. Since IQ is strongly influenced by family environment before puberty, a much larger sample would have been needed to show a significant difference between the two groups."
My reply: Should this really matter for racial gaps that are genetic in origin? The black-white gap in the US still exists among those aged 5-13, so why shouldn't it in Germany? Also, in the Minnesota Transracial Adoption Study, the IQ gaps between blacks, whites, and hybrids did not widen between ages 7 and 17 (when adjusting for attrition in the follow-up at age 17).
In summary, the fathers of these biracials could be expected to have a genotypic IQ of at most 90. This is still 11 points below the white soldiers (101). Now, the children would only be half "black", so the difference should be halved, to 5.5 points lower than the children of the white soldiers.
There's a possibility that blacks who had relationships with white German women had a higher IQ than the black average. In Kirkegaard and Jensen (2023) (https://www.researchgate.net/publication/377216642_Predictors_of_Engaging_in_Interracial_Dating), black men whose first partner was white had an IQ of 89, 4 points above the black mean. But, white women whose first partner was black were also NEGATIVELY selected from the white mean (IQ of 93), thus cancelling out the positive selection of black men. Offspring of white-black relationships thus tend to have intermediate IQs between that of their parents. We don't know how much IQ selectivity applied to black soldiers and German women in 1940s Germany in that unusual environment. In any case, in picking his black and white subjects, Eyferth matched them for their mother's socioeconomic status (most were lower-class). So the mothers of the black and white children would've been matched for IQ to some degree, if there even was an IQ difference to begin with.
So let's investigate the possibility of assortative mating. Now, as noted earlier, blacks in the army would have a phenotypic IQ of 91.5, 6.5 points above the black mean. Let's assume that those who had relationships with German women had an IQ as much as 4 points above the black mean, so 95.5. This would be 10.5 points above the black mean. With regression to the mean, this advantage shrinks to 7.35 points (assuming narrow heritability of 0.7, therefore 10.5×0.7=7.35). The AGCT correlates 0.77 with the Wechsler among whites, but as noted earlier, possibly between 0.3 to 0.77 among blacks. Let's assume the correlation was 0.5. This would further bring down the advantage to 3.68 points (7.35×0.5=3.68). Add this to the black mean of 85 and we get 88.68. Let's assume that the North Africans, who numbered 25% at most, also had an IQ 3.68 points above their mean, and that their genotypic mean is 89. This would bring their IQ to 92.68. Their comprising 25% of the "black" fathers would raise the genotypic IQ of the group to 89.68.
We can draw the conclusion that the "black" fathers of these German children had a genotypic IQ of less than 90. Let's say 89. The mothers most likely had a genotypic IQ slightly below average, say 97. The half-black children should have an intermediate IQ, so 93. White soldiers had an IQ of 101, so their offspring with German mothers should have an IQ of 99. Thus, there should be a 6-point gap between the black and white children.
The actual IQ of the black children was 96.5, and 94 when adjusted for the Flynn effect. This is nearly identical to their expected IQ of 93. The white children had an actual IQ of 97.2, and 94 when adjusted for the Flynn effect. This is 5 points lower than their expected IQ of 99. And here is the problem with the study.
There's a much simpler explanation for the disappearance of the gap than what Rushton and Jensen suggested: sampling error. Jensen (1998) actually argued this in his The g factor: The Science of Mental Ability. In the white sample, the boys had an IQ of 101 and the girls 93, a bizarre gap of 8 points. In the black sample however, boys and girls scored nearly identical IQs of 97 and 96 respectively. There was no sex difference in the WISC standardization, suggesting a sampling error in the white sample.
In other words, the main reason that the white sample scored the same as the black sample was because of the very low score of white girls.
Now, the black-white gap is generally larger on the more g-loaded items, and this is to be expected if the gap is genetic (although it doesn't prove a genetic origin of the gap). However, the gap did not increase with g-loading in the Eyferth study; there was no correlation with g, so that's curious. I'm not sure if the g-loading of the gap can disappear simply because of sampling (e.g. even an elite group of blacks should still do better on the less g-loaded items and worse on the more g-loaded items).
- "blacks in the military should have had an IQ of 91.5" - First, Rushton wasn't assuming that this factor alone would account for Eyferth's findings. Second, Flynn is applying the 30% rejection rate of Black enlistees to the African American mean of 85%. He is forgetting that the process of enlistment, by its very nature, tends to screen out the less intelligent. To take an extreme example, a mentally incompetent person would not even be capable of going through the enlistment process. So there is a process of elimination before the enlistee sits down and takes the IQ test.
- "Let's assume the North African soldiers had an IQ as high as 93." You're mistaken. North African IQ is in the mid to high 90s. Also, the French army, like the US army, rejected applicants below a certain IQ level.
- "Should this really matter for racial gaps that are genetic in origin?" Yup. Cognitive ability is much more malleable during early childhood.
What evidence is there that North African IQ is in the mid to high 90s? All studies of Moroccan second-generation immigrants in the Netherlands give IQs in the high 80s, rarely above 90. The same is broadly true for Middle Eastern groups. Comparing the educational level of Moroccans who migrated to the Netherlands to those who stayed behind in Morocco shows no significant negative or positive selection (https://link.springer.com/content/pdf/10.1007/s10680-018-9484-2.pdf).
Again, let's say the blacks in the military were even more selected than what Flynn calculated. Let's give them an IQ as high as 95. With regression to the mean (0.7) and the correlation between the AGCT and the Wechsler (0.5), this 10-point advantage shrinks to only 3.5 points (10x0.7x0.5=3.5). Add this to the black mean of 85 and we get 88.5. Not so high. Or we can even see what happens if we assume their IQ was as high as 99. This would shrink to a genotypic Wechsler IQ of 89.9 after the necessary adjustments. There would still be a genotypic black-white gap of at least 10 points in the military.
Cognitive ability is more malleable during early childhood, but the while the Minnesota Transracial Adoption study showed higher overall IQs for blacks, whites and mixes, the GAPS between the three groups did not change from childhood to late adolescence. And I'm not sure if the white lower-class single mothers in Germany at that time provided such a good environment.
As for the studies of Moroccan immigrants in the Netherlands, I have little confidence in IQ tests that are not administered in the first language of the people being tested.
2. You keep assuming that the regression would be to a mean of 85. Keep in mind that this was a select group whose mean would necessarily be higher. If you select out the mentally incompetent individuals, it's not just the phenotypic mean that becomes higher. It's also the genotypic mean.
Again, no one is claiming that this was the only explanatory factor.
3. Genetic influences can be age-dependent. It is well established that the human brain is much more malleable during early childhood than later in life. This is why family socialization effects are typically stronger in early childhood. The environmental component of IQ is thus larger.
You're arguing against yourself when you point out that the mothers in the Eyferth study provided a less enriched environment than the families in the Minnesota adoption study. The environmental component of IQ is thus larger in the German study than in the Minnesota study because the German mothers weren't pushing their children to the phenotypic limit. There is thus a lower likelihood of finding a significant difference between the two groups of German children.
The national IQs from the site that you posted are completely useless. They're from an online IQ test measuring those who entered the site and took the test. As a result, the IQs are very weird, e.g. IQ of 106 for Iran, 103 for Armenia, 102 for Sri Lanka, 99 for Lebanon, etc. The lowest scoring country (Gabon) scores no lower than 85. This list shouldn't be used for anything.
If we look at the actual, real national IQ collections, such as those made by Becker and Lynn, North African countries have IQs in in the range 67-81 (Becker, 2023) or mid-80s (Lynn & Vanhanen, 2012).
North Africans born and raised in Europe have higher IQs in the high-80s. And this is almost exclusively on nonverbal tests, so we don't need to worry about language bias.
"You keep assuming that the regression would be to a mean of 85. Keep in mind that this was a select group whose mean would necessarily be higher. If you select out the mentally incompetent individuals, it's not just the phenotypic mean that becomes higher. It's also the genotypic mean."
Yes, and I did not contradict this. If blacks in the military have an IQ as much as 10 points above the black mean (doubtful), then about 70% of that advantage should be genetic and passed on to their children (narrow heritability of 0.7). So while they would have a phenotypic IQ of 95, their genotypic IQ would be 92.
Why would it not regress toward the black mean of 85? WW2 was just two or so generations after the abolition of slavery, so I doubt there'd be an established subgroup of high IQ blacks whose mean they would regress toward.
And again, the advantage of elite selection would further shrink because the AGCT correlates imperfectly with Wechsler IQ. Blacks in the military most likely had a genotypic IQ of 90 at most. Most of the gap was not eliminated.
IQ is highly malleable among children, but what would happen to the black-white gap if black and white children were raised in the exact same environment?
That map is similar to maps based on the findings of Lynn & Vanhanen. Is it reliable for specific countries? Not really, but the same can be said for Lynn & Vanhanen's work.
Even for specific countries, that map is not too far off:
Armenians have a mean IQ of 102? Seems about right.
Gabonese have a mean IQ of 85? Seems close. Wicherts et al. (2010) estimated the mean IQ of SSA at 80
Wicherts, J. M., Dolan, C. V., Carlson, J. S., & van der Maas, H. L. (2010). Raven's test performance of sub-Saharan Africans: Average performance, psychometric properties, and the Flynn Effect. Learning and Individual Differences, 20(3), 135-151. https://doi.org/10.1016/j.lindif.2009.12.001
In the case of North Africa, we don't have many reliable studies. The studies I've seen involve populations that 1) did the test in a language that was not their mother tongue and/or 2) were at a cultural level where tests and test-taking were still recent.
For what it's worth, the best-controlled study found no significant difference in IQ between North African and French children placed in foster care or residential care. Admittedly, I have doubts about that study. The French children were more likely to have psychological problems and more likely to have mothers who had likewise been raised as foster children.
Anaut, M., Chouvier, B., & Tyrrell, J. (2020). North African and French children placed in care: A comparative study of psychosocial and educational outcomes. In Merging Past, Present, and Future in Cross-cultural Psychology (pp. 442-449). Garland Science.
"Why would it not regress toward the black mean of 85?"
Because the men in that subgroup had children with German women and not with random African American women. So their children could not possibly regress to the African American mean of 85.
"Blacks in the military most likely had a genotypic IQ of 90 at most."
- No way. This was before the lowering of IQ requirements in 1966:
"In October 1966, Secretary of Defense Robert McNamara launched “Project 100,000,” under which the Pentagon deliberately lowered the minimum Armed Forces Qualification Test (AFQT) score for induction to the 10th percentile—a drop of about six percentile points from prior standards—to meet escalating manpower demands during the Vietnam War"
"IQ is highly malleable among children, but what would happen to the black-white gap if black and white children were raised in the exact same environment?"
The gap might not be significant. There would be more variability in the IQ of both groups. In fact, there was a reduction in variability as the cohorts grew older in the Minnesota study. I would further argue that the family environment provided by the Minnesota parents was less variable than that provided by most white American parents.
Lynn & Vanhanen and Becker etc. are more reliable, since they summarize multiple real studies with real IQ tests, unlike that online IQ test website. I wouldn't use that online IQ result to argue that North Africans have IQs in the mid to high 90s. It's the only data showing that and contradicts all other (and better) data.
Armenians are basically West Asian and there's no evidence that an IQ of 102 is about right (in fact, it's around 90 and the same is true of Armenians born in the US according to an old study using a nonverbal test). If the IQ in Gabon is 85, same as African-Americans, it suggests that the African environment has no effect whatsoever on the African IQ, or that the African-American environment is just as bad as that of Africa, both of which are absurd.
It doesn't matter so much what the IQ is in North Africa, but rather what their IQ is when raised in Western countries. North Africans born and raised in the Netherlands have IQs that are often below 90, on strictly nonverbal tests. See for example te Nijenhuis' meta-analysis: http://dx.doi.org/10.1002/per.511. And there are more recent studies confirming this. There's no real reason to believe these results aren't real. Nonverbal IQ tests are rarely biased against minorities raised in Western countries. See for example studies on test bias in the US, where tests do not seem to be biased against US-born Hispanics, who are of immigrant background.
I'd like to take a look at that study of foster children in France as it sounds interesting, but I'm unable to access it. Are you able to send it somehow (e.g. through DMs)?
It's not a problem with regression to the mean that the children were half-black. I've been using regression to the mean and genotypic IQ a bit interchangeably since they both involve the same heritability adjustment. But we can forget about regression to the mean and simply calculate the genotypic IQ of blacks in the military. Again, if blacks in the army were phenotypically as much as 10 points above the black mean (unlikely), their genotypic IQ would be ~7 points above the black mean, so 92 (again, this is because heritability of course is not 100%). Then, since the AGCT is not a perfect IQ test, their IQ would be lower still (correlation with Wechsler of 0.77 at most).
I don't see any way in which the genotypic IQ of blacks in the Army could not have been 90 at most.
I know this one. It's Willerman et al, 1974:
https://lesacreduprintemps19.files.wordpress.com/2013/04/willerman-et-al-1974.pdf
It's unpersuasive, to say the least. Very young children (age 4), very small number of children with black mothers, and extremely noisy data. Glad well didn't imagine this study, but he certainly imagined its findings to be much more more robust and generalizable than they actually are.
Also, both mothers and fathers in the white female/black male couples were more educated than the black female/white male couples. And the latter actually had slightly higher incomes on average, ruling out poverty as an explanation for the gap.
Interesting. This study isn't mentioned in Flynn's article. It may be that Malcolm Gladwell was inserting his memory of this study into his memory of Flynn's presentation.
I've rewritten my post to discuss the findings of the Willerman et al. study.
Not on topic, but it would be interesting to hear your comments on this new paper providing genomic evidence for Gregory Clark's theory of the fundamental cause of the industrial revolution:
https://www.researchgate.net/publication/392808200_Genomic_Evidence_for_Clark's_Theory_of_the_British_Industrial_Revolution
This is fascinating! I was expecting that Davide Piffer would repeat his earlier study with a larger sample of genomes, but this study has come earlier than expected. It provides a more detailed look at the increase in mean cognitive ability of the English population between 1000 and 1850.
Two preliminary observations:
- It looks like there was an acceleration and then a deceleration, with most of the increase occurring between 1400 and 1700.
- The increase in the "smart fraction" is impressive. The top 1% in 1850 was equal to the top 0.01% in the year 1000. This finding points to a considerable increase in the subpopulation of highly intelligent people above and beyond what would be expected from population growth alone. Intellectuals were no longer voices crying in the wilderness. They could now meet and socialize with other intellectuals. It was this potential for synergy that caused the Enlightenment and then the Industrial Revolution.
I am thinking that EA might not be the best estimate for what intellectual contributions one might expect from a population, though it obviously nevertheless correlates strongly. I remember that there was a strange discrepancy between the IQ and EA polygenic scores of Ancient Greeks in Evolutionary Trends of Polygenic Scores in European Populations From the Paleolithic to Modern Times. The Romans had higher EA polygenic scores, yet their intellectual contributions were mostly derivative of Greek innovations: verism from Hellenistic art, De Rerum Natura from Epicureanism, encyclopedic compilations based mostly on Greek thought (Pliny the Elder's Encyclopedia), etc. Roman contributions were mostly in (very good) fundamentals: for example, Cicero noted that the Roman Twelve Tables "surpass the libraries of all the philosophers, both in weight of authority and in plenitude of utility." Or consider this citation from a Greek observer: "The extraordinary greatness of the Roman Empire manifests itself above all in three things: the aqueducts, the paved roads, and the construction of the drains." Could these not be compared to the excellent idea of civil exams or what Francis Bacon called the "great inventions" ("printing, gunpowder, and the magnet") of Chinese civilization? There is even a quote parallel to that of Cicero: "... no empire, no sect, no star, seems to have exerted greater power and influence in human affairs than these three mechanical discoveries."
I suspect that verbal intelligence might be even more closely related to innovation than something like spatial intelligence, yet both would (I suppose) be measured as if they were equivalent by IQ polygenic scores. What I notice most from Greek civilization is an extreme capacity for meta-reflection and a unique tolerance for ambiguity, as can notably be seen in plays like the Oresteia and Antigone, or in the mere existence of people like Socrates and Aristotle. My guess is that La Griffe du Lion was onto something when he attributed an outsized influence to verbal IQ. There is a unique disposition to not simply wish to recompilate like Pliny the Elder (Roman) or Vincent de Beauvais (Medieval French) did.
A significant portion of EA polygenic scores may reflect non-cognitive factors, notably monotony avoidance and the ability to sit still in a classroom.
Can you tell me where in that paper the authors say that the Romans had higher EA polygenic scores than the Greeks?
If you check Figures S14 and S15 of the supplementary material, you can see that Iron Age Italy has the highest EA scores. The authors note, "The overall rankings were quite similar, with the lowest scores for hunter-gatherers, Neolithic Middle Easterners, and Copper Age Iberians, and the highest for Iron Age and medieval Italy (Supplementary Figures S14, S15, S16)." Figures S14 through S16 also show that the Bronze Age Greeks had middling EA scores but the highest IQ PGS. As the study states, "A significant divergence was noted in the sample of ancient Greeks from the Bronze Age in the comparison between IQ and EA. The Bronze Age Greeks, while displaying average scores on EA, manifested the highest scores in IQ PGS." Something else I’ve found interesting is that the decline in IQ PGS observed in Imperial Italy is not as dramatic as the decline in EA PGS.
To be fair, throughout this discussion I’ve been referring to the accomplishments of Classical Greece, whereas the study specifically measures the scores of Bronze Age Greeks. While there might have been some continuity in selection across periods, a dark age followed immediately after the Bronze Age, which suggests a potential cognitive decline. Moreover, it’s not clear which Bronze Age Greeks are represented. Minoans, Mycenaeans, or both? In my opinion, the Minoans were more impressive. Perhaps the Ancient Greeks followed a pattern similar to the Italian populations, with periods of high intelligence interrupted by one notable decline. The Greeks truly deserve a thorough, period-by-period analysis of their cognitive traits. I guess remains that don't show selection bias could be recovered from mass graves caused by massacres, plagues, or shipwrecks (they found one skeleton in the Antikythera wreck)?
Peter Frost’s What do you think of this blog post?This person tries to claim that the recent differences between whites and blacks and their outcomes is due to geography and other confounding factors like and starvation.
And they also claim that recent data has challenged the hereditarian hypothesis https://erikexamines.substack.com/p/iq-race-and-racism
I'll try to respond point by point:
1. Minnesota Transracial Adoption Study
"Several white adopted children with low IQ scores were lost from the follow-up studies. The Black adopted children who were lost did not have unusually low IQs."
There were losses of participants in all four groups of children: 1) nonadopted, White biological parents; 2) adopted, two White biological parents; 3) adopted, one White and one Black biological parent; 4) adopted, two Black biological parents. Proportionately, the losses were about the same in all four groups
The children were measured for IQ at age 7 and again at age 17. The relative ranking of the four groups of children remained the same. If loss of participants "skewed" the data, it must have had exactly the same impact on each group.
------------------------ Age 7 Age 17
1) biological parents - 120 115
2) nonadopted, White - 117 109
3) adopted, White and White - 112 106
4) adopted, White and Black - 109 99
5) adopted, Black and Black - 97 89
All of the groups, including the adoptive parents, experienced a decline in IQ. There is some argument over whether this decline was due to renorming of the IQ tests or to a natural decline in learning ability with age.
As for the Flynn effect, some people think it is an intergenerational effect. If it is intergenerational, it wouldn't apply here, since we're dealing with the same generation. If it does apply here, the actual decline in IQ with age is even larger. So there are even fewer benefits from growing up in the enriched environment of middle-class Minnesota families.
Heritability of IQ Score
Yes, genetic differences become less important as environmental differences become more important. This is Logic 101. And this is why we should focus either on adoption studies or on direct measurement of the genetic component of IQ, i.e., alleles associated with IQ or educational attainment.
Is Heritability a Sensible Concept?
Again, Logic 101. If you increase environmental variability, hereditable variability becomes relatively less important. None of this invalidates heritability. It's like saying that the risk of death from smoking is nothing compared to being in Cambodia during the Khmer Rouge.
High Test Scores of Black British Immigrant Children
First, we're no longer talking about IQ tests. We're talking about the GCSE. Success on the GCSE is strongly influenced by coaching (and cheating).
Second, most Black British children do poorly on the GCSE. Unusual high rates of success are found among Nigerian students, especially Igbo. This success is due partly to coaching and partly to diligence in doing homework and attending classes. It may also have genetic causes.
Africa is a continent with a variety of populations, and IQ varies within Africa as it does within Europe. IQ seems to be higher in populations that have a longer history of trade and other forms of social complexity. This is notably the case with the Igbo, who acted as middlemen in trade between the coast and the interior via the Niger River. To some extent, it's true for other populations close to the Niger.
In general, rivers seem to have an organizational effect on human communities, boosting trade, social complexity and, hence, selection for cognitive ability. https://www.anthro1.net/p/west-africa-and-recent-cognitive
The Black-White IQ Gap Myth
"blacks today aged 12 have a mean IQ of about 90.5; and young blacks have gained 5.52 points on whites over 30 years"
This is due largely to changes within the "Black" and "White" categories. A process of convergence is occurring through mass immigration. "Whites" increasingly include lower-performing groups, while "Blacks" increasingly include higher-performing groups, like Nigerian immigrants. Another factor is that biracial children have become proportionately more numerous, and they are usually categorized as "Black."
I won't discuss the issue of crime because it's influenced not only by cognitive ability but also by propensity for violence. In many traditional societies, violence is limited by a "balance of terror" — a murder will be avenged by the victim's male siblings and male cousins. Violence increases when this balance of terror is no longer operational.
This is the case in pacified societies where the State has long exercised a monopoly on the use of violence. A murder will not be avenged by the victim's male kin because that sort of vengeance has long been suppressed by the State.
https://www.anthro1.net/p/1-genetic-pacification-in-western
The three reasons given by Rushton and Jensen for the disappearance of the black-white gap in the Eyferth study are not convincing. None of the factors they describe eliminates the gap significantly.
First point: "The African American soldiers in Germany were (...) a higher-IQ sample of the African American population."
My reply: Hardly true. Flynn's (1980, p. 84-94) detailed calculations in his "Race, IQ, and Jensen", which has received disappointingly little attention by hereditarians, show that blacks in the military should have had an IQ of 91.5, and even lower when taking into account regression to the mean and the imperfect correlation between the Army General Classification Test (AGCT) scores and Wechsler IQ. He estimated that regression to the mean would put it at 89.55 at most (narrow heritability of 0.7, so (91.5-85)×0.7+85=89.55). Then, the AGCT correlates 0.77 with the Wechsler among whites, but since the test contained questions related to school-taught knowledge and blacks had very few years of schooling at that time, and were arguably less motivated to take the test to serve in the military (e.g. some failed on purpose) (Flynn, 1980, p. 226), the correlation between the AGCT and Wechsler IQ for blacks could've been anywhere from .30 to .77 (p. 221), so this would further have lowered their IQ to 88.5 AT MOST.
Second point: "Between 20 and 25% of the 'black' fathers were, in fact, North African".
My reply: That doesn't make much a difference. North Africans seem to have an IQ around ~89 when raised in Europe, so let's assume that that's their genotypic mean IQ. Let's assume the North African soldiers constituted as much as 25% and had an IQ as high as 93 (adjusted for regression to the mean). Still, that would only raise the genotypic mean IQ of the "black" soldiers by 1.1 points – to 89.6. That's not much.
Third point: "The children were still young when tested. One third were between 5 and 10 years old and two thirds between 10 and 13. Since IQ is strongly influenced by family environment before puberty, a much larger sample would have been needed to show a significant difference between the two groups."
My reply: Should this really matter for racial gaps that are genetic in origin? The black-white gap in the US still exists among those aged 5-13, so why shouldn't it in Germany? Also, in the Minnesota Transracial Adoption Study, the IQ gaps between blacks, whites, and hybrids did not widen between ages 7 and 17 (when adjusting for attrition in the follow-up at age 17).
In summary, the fathers of these biracials could be expected to have a genotypic IQ of at most 90. This is still 11 points below the white soldiers (101). Now, the children would only be half "black", so the difference should be halved, to 5.5 points lower than the children of the white soldiers.
There's a possibility that blacks who had relationships with white German women had a higher IQ than the black average. In Kirkegaard and Jensen (2023) (https://www.researchgate.net/publication/377216642_Predictors_of_Engaging_in_Interracial_Dating), black men whose first partner was white had an IQ of 89, 4 points above the black mean. But, white women whose first partner was black were also NEGATIVELY selected from the white mean (IQ of 93), thus cancelling out the positive selection of black men. Offspring of white-black relationships thus tend to have intermediate IQs between that of their parents. We don't know how much IQ selectivity applied to black soldiers and German women in 1940s Germany in that unusual environment. In any case, in picking his black and white subjects, Eyferth matched them for their mother's socioeconomic status (most were lower-class). So the mothers of the black and white children would've been matched for IQ to some degree, if there even was an IQ difference to begin with.
So let's investigate the possibility of assortative mating. Now, as noted earlier, blacks in the army would have a phenotypic IQ of 91.5, 6.5 points above the black mean. Let's assume that those who had relationships with German women had an IQ as much as 4 points above the black mean, so 95.5. This would be 10.5 points above the black mean. With regression to the mean, this advantage shrinks to 7.35 points (assuming narrow heritability of 0.7, therefore 10.5×0.7=7.35). The AGCT correlates 0.77 with the Wechsler among whites, but as noted earlier, possibly between 0.3 to 0.77 among blacks. Let's assume the correlation was 0.5. This would further bring down the advantage to 3.68 points (7.35×0.5=3.68). Add this to the black mean of 85 and we get 88.68. Let's assume that the North Africans, who numbered 25% at most, also had an IQ 3.68 points above their mean, and that their genotypic mean is 89. This would bring their IQ to 92.68. Their comprising 25% of the "black" fathers would raise the genotypic IQ of the group to 89.68.
We can draw the conclusion that the "black" fathers of these German children had a genotypic IQ of less than 90. Let's say 89. The mothers most likely had a genotypic IQ slightly below average, say 97. The half-black children should have an intermediate IQ, so 93. White soldiers had an IQ of 101, so their offspring with German mothers should have an IQ of 99. Thus, there should be a 6-point gap between the black and white children.
The actual IQ of the black children was 96.5, and 94 when adjusted for the Flynn effect. This is nearly identical to their expected IQ of 93. The white children had an actual IQ of 97.2, and 94 when adjusted for the Flynn effect. This is 5 points lower than their expected IQ of 99. And here is the problem with the study.
There's a much simpler explanation for the disappearance of the gap than what Rushton and Jensen suggested: sampling error. Jensen (1998) actually argued this in his The g factor: The Science of Mental Ability. In the white sample, the boys had an IQ of 101 and the girls 93, a bizarre gap of 8 points. In the black sample however, boys and girls scored nearly identical IQs of 97 and 96 respectively. There was no sex difference in the WISC standardization, suggesting a sampling error in the white sample.
In other words, the main reason that the white sample scored the same as the black sample was because of the very low score of white girls.
Now, the black-white gap is generally larger on the more g-loaded items, and this is to be expected if the gap is genetic (although it doesn't prove a genetic origin of the gap). However, the gap did not increase with g-loading in the Eyferth study; there was no correlation with g, so that's curious. I'm not sure if the g-loading of the gap can disappear simply because of sampling (e.g. even an elite group of blacks should still do better on the less g-loaded items and worse on the more g-loaded items).
- "blacks in the military should have had an IQ of 91.5" - First, Rushton wasn't assuming that this factor alone would account for Eyferth's findings. Second, Flynn is applying the 30% rejection rate of Black enlistees to the African American mean of 85%. He is forgetting that the process of enlistment, by its very nature, tends to screen out the less intelligent. To take an extreme example, a mentally incompetent person would not even be capable of going through the enlistment process. So there is a process of elimination before the enlistee sits down and takes the IQ test.
- "Let's assume the North African soldiers had an IQ as high as 93." You're mistaken. North African IQ is in the mid to high 90s. Also, the French army, like the US army, rejected applicants below a certain IQ level.
- "Should this really matter for racial gaps that are genetic in origin?" Yup. Cognitive ability is much more malleable during early childhood.
What evidence is there that North African IQ is in the mid to high 90s? All studies of Moroccan second-generation immigrants in the Netherlands give IQs in the high 80s, rarely above 90. The same is broadly true for Middle Eastern groups. Comparing the educational level of Moroccans who migrated to the Netherlands to those who stayed behind in Morocco shows no significant negative or positive selection (https://link.springer.com/content/pdf/10.1007/s10680-018-9484-2.pdf).
Again, let's say the blacks in the military were even more selected than what Flynn calculated. Let's give them an IQ as high as 95. With regression to the mean (0.7) and the correlation between the AGCT and the Wechsler (0.5), this 10-point advantage shrinks to only 3.5 points (10x0.7x0.5=3.5). Add this to the black mean of 85 and we get 88.5. Not so high. Or we can even see what happens if we assume their IQ was as high as 99. This would shrink to a genotypic Wechsler IQ of 89.9 after the necessary adjustments. There would still be a genotypic black-white gap of at least 10 points in the military.
Cognitive ability is more malleable during early childhood, but the while the Minnesota Transracial Adoption study showed higher overall IQs for blacks, whites and mixes, the GAPS between the three groups did not change from childhood to late adolescence. And I'm not sure if the white lower-class single mothers in Germany at that time provided such a good environment.
1. https://worldpopulationreview.com/country-rankings/average-iq-by-country
As for the studies of Moroccan immigrants in the Netherlands, I have little confidence in IQ tests that are not administered in the first language of the people being tested.
2. You keep assuming that the regression would be to a mean of 85. Keep in mind that this was a select group whose mean would necessarily be higher. If you select out the mentally incompetent individuals, it's not just the phenotypic mean that becomes higher. It's also the genotypic mean.
Again, no one is claiming that this was the only explanatory factor.
3. Genetic influences can be age-dependent. It is well established that the human brain is much more malleable during early childhood than later in life. This is why family socialization effects are typically stronger in early childhood. The environmental component of IQ is thus larger.
You're arguing against yourself when you point out that the mothers in the Eyferth study provided a less enriched environment than the families in the Minnesota adoption study. The environmental component of IQ is thus larger in the German study than in the Minnesota study because the German mothers weren't pushing their children to the phenotypic limit. There is thus a lower likelihood of finding a significant difference between the two groups of German children.
The national IQs from the site that you posted are completely useless. They're from an online IQ test measuring those who entered the site and took the test. As a result, the IQs are very weird, e.g. IQ of 106 for Iran, 103 for Armenia, 102 for Sri Lanka, 99 for Lebanon, etc. The lowest scoring country (Gabon) scores no lower than 85. This list shouldn't be used for anything.
If we look at the actual, real national IQ collections, such as those made by Becker and Lynn, North African countries have IQs in in the range 67-81 (Becker, 2023) or mid-80s (Lynn & Vanhanen, 2012).
North Africans born and raised in Europe have higher IQs in the high-80s. And this is almost exclusively on nonverbal tests, so we don't need to worry about language bias.
"You keep assuming that the regression would be to a mean of 85. Keep in mind that this was a select group whose mean would necessarily be higher. If you select out the mentally incompetent individuals, it's not just the phenotypic mean that becomes higher. It's also the genotypic mean."
Yes, and I did not contradict this. If blacks in the military have an IQ as much as 10 points above the black mean (doubtful), then about 70% of that advantage should be genetic and passed on to their children (narrow heritability of 0.7). So while they would have a phenotypic IQ of 95, their genotypic IQ would be 92.
Why would it not regress toward the black mean of 85? WW2 was just two or so generations after the abolition of slavery, so I doubt there'd be an established subgroup of high IQ blacks whose mean they would regress toward.
And again, the advantage of elite selection would further shrink because the AGCT correlates imperfectly with Wechsler IQ. Blacks in the military most likely had a genotypic IQ of 90 at most. Most of the gap was not eliminated.
IQ is highly malleable among children, but what would happen to the black-white gap if black and white children were raised in the exact same environment?
That map is similar to maps based on the findings of Lynn & Vanhanen. Is it reliable for specific countries? Not really, but the same can be said for Lynn & Vanhanen's work.
Even for specific countries, that map is not too far off:
Armenians have a mean IQ of 102? Seems about right.
Gabonese have a mean IQ of 85? Seems close. Wicherts et al. (2010) estimated the mean IQ of SSA at 80
Wicherts, J. M., Dolan, C. V., Carlson, J. S., & van der Maas, H. L. (2010). Raven's test performance of sub-Saharan Africans: Average performance, psychometric properties, and the Flynn Effect. Learning and Individual Differences, 20(3), 135-151. https://doi.org/10.1016/j.lindif.2009.12.001
In the case of North Africa, we don't have many reliable studies. The studies I've seen involve populations that 1) did the test in a language that was not their mother tongue and/or 2) were at a cultural level where tests and test-taking were still recent.
For what it's worth, the best-controlled study found no significant difference in IQ between North African and French children placed in foster care or residential care. Admittedly, I have doubts about that study. The French children were more likely to have psychological problems and more likely to have mothers who had likewise been raised as foster children.
Anaut, M., Chouvier, B., & Tyrrell, J. (2020). North African and French children placed in care: A comparative study of psychosocial and educational outcomes. In Merging Past, Present, and Future in Cross-cultural Psychology (pp. 442-449). Garland Science.
"Why would it not regress toward the black mean of 85?"
Because the men in that subgroup had children with German women and not with random African American women. So their children could not possibly regress to the African American mean of 85.
"Blacks in the military most likely had a genotypic IQ of 90 at most."
- No way. This was before the lowering of IQ requirements in 1966:
"In October 1966, Secretary of Defense Robert McNamara launched “Project 100,000,” under which the Pentagon deliberately lowered the minimum Armed Forces Qualification Test (AFQT) score for induction to the 10th percentile—a drop of about six percentile points from prior standards—to meet escalating manpower demands during the Vietnam War"
https://en.wikipedia.org/wiki/Project_100,000
"IQ is highly malleable among children, but what would happen to the black-white gap if black and white children were raised in the exact same environment?"
The gap might not be significant. There would be more variability in the IQ of both groups. In fact, there was a reduction in variability as the cohorts grew older in the Minnesota study. I would further argue that the family environment provided by the Minnesota parents was less variable than that provided by most white American parents.
Lynn & Vanhanen and Becker etc. are more reliable, since they summarize multiple real studies with real IQ tests, unlike that online IQ test website. I wouldn't use that online IQ result to argue that North Africans have IQs in the mid to high 90s. It's the only data showing that and contradicts all other (and better) data.
Armenians are basically West Asian and there's no evidence that an IQ of 102 is about right (in fact, it's around 90 and the same is true of Armenians born in the US according to an old study using a nonverbal test). If the IQ in Gabon is 85, same as African-Americans, it suggests that the African environment has no effect whatsoever on the African IQ, or that the African-American environment is just as bad as that of Africa, both of which are absurd.
It doesn't matter so much what the IQ is in North Africa, but rather what their IQ is when raised in Western countries. North Africans born and raised in the Netherlands have IQs that are often below 90, on strictly nonverbal tests. See for example te Nijenhuis' meta-analysis: http://dx.doi.org/10.1002/per.511. And there are more recent studies confirming this. There's no real reason to believe these results aren't real. Nonverbal IQ tests are rarely biased against minorities raised in Western countries. See for example studies on test bias in the US, where tests do not seem to be biased against US-born Hispanics, who are of immigrant background.
I'd like to take a look at that study of foster children in France as it sounds interesting, but I'm unable to access it. Are you able to send it somehow (e.g. through DMs)?
It's not a problem with regression to the mean that the children were half-black. I've been using regression to the mean and genotypic IQ a bit interchangeably since they both involve the same heritability adjustment. But we can forget about regression to the mean and simply calculate the genotypic IQ of blacks in the military. Again, if blacks in the army were phenotypically as much as 10 points above the black mean (unlikely), their genotypic IQ would be ~7 points above the black mean, so 92 (again, this is because heritability of course is not 100%). Then, since the AGCT is not a perfect IQ test, their IQ would be lower still (correlation with Wechsler of 0.77 at most).
I don't see any way in which the genotypic IQ of blacks in the Army could not have been 90 at most.