Race and intelligence

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Human races differ in average intelligence for genetic reasons [1]. With the inception of IQ testing in the early 20th century, differences in average test performance between racial groups were observed, and these differences have remained stable through time [2][3]. Simplifying the issue, modern science has concluded that race is a biological reality rather than a social construct [4], and there exists one consensus definition of intelligence, i.e. general intelligence score [5]. The validity of IQ testing as a metric for human intelligence is not disputed. Today, the scientific consensus is that genetics explain most or all of the differences in IQ test performance between groups [6].

Pseudoscientific denialism of inherent differences in intelligence between races have played a central role in the history of blank slatism. In the 1920s, groups of Marxist lobbyists argued that race is a social construct [7]. In turn, they used such beliefs to justify anti-white policies. In recent decades, as understanding of the human genome has advanced, claims of inherent differences in intelligence between races have been broadly accepted by scientists on both theoretical and empirical grounds.

Development of the IQ Test

It’s reasonable to claim that the biggest success story in the history of psychology research is the development of the IQ test. An IQ test is a serious predictive tool, unlike most of what is put out by “social psychologists,” “behavioral scientists,” “behavioral economics,” “nudge theorists,” and so on. For a taste of IQ’s success, one meta-analysis with a combined sample size of over 90,000 people found that IQ is the most powerful known predictor of subjects’ levels of occupation, education, and income.[8]

The Black-White IQ Gap

Stability of the Gap

As Charles Murray and Richard Herrnstein argued in The Bell Curve, IQ is extremely relevant to social policy. There is a gap between the average scores of white test takers and black test takers of about 15 IQ points, or one standard deviation. This black-white IQ gap has been measured since the 1960’s. Occasionally, some claim it has shrunk, often through the use of tests with poor predictive validity and non-random samples.

Following claims of a shrinking gap, a 2012 meta-analysis conclusively found no such evidence of shrinkage,[9] meaning the black-white IQ gap had remained stable for almost 50 years after the Civil Rights movement, which led to the government becoming extremely financially supportive of blacks through desegregation and affirmative action.

A recent, representative sample of 12,000 found a black-white IQ gap of over 18 points.[10] The gap is not closing despite over half a century of welfare to blacks.

The Gap and Race Disparities

When controlling for IQ, huge chunks of most racial performance gaps vanish.[11] When they have the same IQ as whites, blacks are more likely than whites to graduate from college and to attain a high status occupation. Blacks, after controlling for IQ, make just as much money as whites and are only 5% more likely to be in poverty than whites.

Heritability

Heritability is an important concept when it comes to understanding the causation behind the variance of a metric like IQ. Heritability is the proportion of variance of a trait that is explained by variance of relevant genetics. With classical techniques, heritability can only be directly measured within a population. Using only classical methods, the “heritability” (proportion of the gap that is due to genetic differences) of the between-groups gap has to be inferred indirectly. Decades of classical behavioral genetics research has provided ample data for such an inference.

Within-Race Heritability of IQ

For first world whites, the within-race heritability of IQ is one of the most well replicated findings of psychology and behavioral genetics. A meta-analysis with a combined sample size of 11,000 twin pairs from white countries found that the narrow sense heritability of IQ is roughly 66% at age 17.[12]

Before the age of 17, the heritability of IQ is usually lower, known as the Wilson Effect. This doesn’t imply that IQ is more permanently malleable in childhood. Intervention programs designed to raise children's IQs often produce effects that fade by adulthood.[13][14] The Wilson Effect might be due to poorer g-loading and reliability of child IQ tests. Child IQ data is less reliable,[15] and this contributes to the Wilson Effect. The reasons for poorer reliability could include test simplicity and developmental differences among children. However, these factors dissipate by adulthood.

Other studies indicate that factors not explained by genetics are mostly attributed to unshared environment,[16][17] which includes elements like peer groups and stochastic effects, excluding family pressures and school quality.

Narrow sense heritability focuses on additive genetic effects, but non-additive genetic factors are also significant. These non-additive factors, not shared between family members, are often categorized under unshared environmental components. Monozygotic twins, sharing all their genes, provide insights into broad sense heritability, with estimates between 75% to 85%.

Implications for the Black-White IQ Gap

The discussion of within-group heritability is not to claim that the heritability of the black-white IQ gap is the same. It establishes that genetics play a significant role in determining IQ within a population, suggesting that genetics might be important in explaining the black-white IQ gap.

Environmental Differences

How do black and white IQ-relevant environments differ on average? If the races have the same IQ-relevant environment on the aggregate, the heritability of the black-white IQ gap is 100%, as the total difference would be due to differences in the two gene pools. Lesser heritability of the gap indicates a poorer black IQ-relevant environment compared to the white IQ-relevant environment.

Race and Heritability

Race is real and plays a significant role in heritability studies, especially concerning the black-white IQ gap. The physical differences between black and white people, such as in kidney functioning, suggest that evolution didn't stop at skin level. Computers can classify ancestry groups by DNA and match self-reported race with 99% accuracy,[18] supporting the notion that race has a biological basis.

A study graphed racial clusters as identified by a computer, finding they matched self-reported race, with Africans being the most divergent.[19] This data, alongside evolutionary theory, suggests a significant heritable component in the black-white IQ gap.

Environmental Factors and the MTRAS

Environmentalists point to three main factors affecting the black-white IQ gap: test bias, physical factors, and psychological factors. The notion that IQ tests are culturally biased has been largely debunked.[20] The Minnesota Transracial Adoption Study (MTRAS) is a key piece of evidence, showing that black and white adoptees raised in similar environments still exhibited the standard IQ gap.[21] This finding suggests that environmental factors like socioeconomic status, nutrition, and school quality do not fully account for the IQ gap.

Furthermore, when the MTRAS data is corrected for the Flynn effect, the racial gaps slightly widen.[22] This correlation suggests that environmental excuses for the IQ gap are insufficient.

Global Trends and Stereotype Threat

Globally, black IQs tend to be lower than white IQs, regardless of the country's history with black populations. Stereotype threat and cultural factors have also been examined but do not fully explain the IQ gap.[23] The MTRAS data, along with other studies, suggest that the black-white IQ gap persists even when controlling for wealth and other environmental factors.

Conclusion

The evidence indicates that the black-white IQ gap is not solely a product of environmental factors or systemic racism. The gap persists globally and across different socioeconomic levels, suggesting a significant genetic component. The narrative of systemic racism falls short in explaining the persistence and consistency of the IQ gap across various contexts.


Other Lines of Classical Evidence

Environmentalism, as a sole explanation for the black-white IQ gap, has been challenged by classical evidence. One significant piece of evidence is sibling regression toward the mean. Studies show that a black sibling of someone with an IQ of 120 will typically have an IQ around 100, whereas a white sibling would average around 110.[24] This suggests differential nonadditive genetic effects and a lack of evidence for an IQ-relevant environment gap. Furthermore, blacks have a smaller standard deviation for IQ than whites,[25] implying that if the environments were similar, black heritability would be higher than white heritability, which is not observed.

The current evidence suggests that the black-white IQ gap is primarily due to differences in IQ-relevant gene pools rather than environmental factors. It is estimated that the heritability of the gap is at least 50%, with some evidence supporting a 100% estimation.

New Evidence: GWAS and Polygenic Scores

A study by Piffer in 2019 revealed that average EDU3 polygenic scores in a population accurately predict the average IQ for that population.[26] The study found that blacks were predicted to have lower genetic IQ scores than what is observed, indicating that environmental interventions might be elevating their IQ above what would be expected based solely on genetics.

The study posits that the difference between the predicted genetic IQ and the actual IQ scores of black populations might be attributed to societal interventions and support systems, such as education and healthcare, which are not originated from within their communities.

New Evidence: Machine Learning and MRI Data

A groundbreaking study by Kirkegaard & Fuerst in 2023 utilized machine learning to analyze MRI brain scan data. The study, which trained a model on 50,000 parameters from a white-only sample, accurately predicted the black sample mean IQ to be 82.[27] This finding indicates a structural difference in IQ, which the study suggests is due to genetic factors or "hard" environmental causes, rather than cultural or psychological factors like stereotype threat.

Despite extensive research and funding over decades, no definitive "hard" environmental cause (such as lead exposure, vitamin D deficiency, or microplastics) has been identified to explain the IQ gap. The study challenges the previously held assumptions about environmental factors being the primary cause of the gap.

New Evidence: Admixture Analysis

Further supporting the genetic argument, a study by Lasker et al. in 2019 showed that the proportion of white ancestry in an individual linearly predicts their IQ.[28] This finding from admixture analysis suggests a genetic basis for the IQ gap, with heritability estimates potentially reaching 100%.

The concept of "colorism" has been brought into the debate, suggesting that lighter-skinned blacks face less oppression and thus perform better on IQ tests. However, when controlling for skin color, the results still support a genetic influence over environmental or cultural factors.




References

  1. ↑ Piffer, D. (2019). Evidence for recent polygenic selection on educational attainment and intelligence inferred from Gwas hits: A replication of previous findings using recent data. Psych, 1(1), 55-75.
  2. ↑ Rushton, J. P. (2012). No narrowing in mean Black–White IQ differences—Predicted by heritable g. American Psychologist, 67(6), 500–501. https://doi.org/10.1037/a0029614
  3. ↑ https://humanvarieties.org/2013/01/15/100-years-of-testing-negro-intelligence/
  4. ↑ Kirkegaard, E. (2021). Genetic ancestry and social race are nearly interchangeable. https://openpsych.net/paper/65/
  5. ↑ Jensen, A. R. (1999). The g factor: The science of mental ability.
  6. ↑ Rindermann, H., Becker, D., & Coyle, T. R. (2020). Survey of expert opinion on intelligence: Intelligence research, experts' background, controversial issues, and the media. Intelligence, 78, 101406.
  7. ↑ MacDonald, K. B. (1998). The culture of critique: An evolutionary analysis of Jewish involvement in twentieth-century intellectual and political movements (p. viii). Westport: Praeger.
  8. ↑ Strenze, T. (2007). Intelligence and socioeconomic success: A meta-analytic review of longitudinal research. Intelligence, 35(5), 401-426.
  9. ↑ Rushton, J. P. (2012). No narrowing in mean Black–White IQ differences—Predicted by heritable g. American Psychologist, 67(6), 500–501.
  10. ↑ Kirkegaard, E. O., & Fuerst, J. G. (2023). A Multimodal MRI-based Predictor of Intelligence and Its Relation to Race/Ethnicity. Mankind Quarterly, 63(3).
  11. ↑ Herrnstein, R. & Murray, C. (1994). The Bell Curve.
  12. ↑ Haworth, C. M., Wright, M. J., Luciano, M., Martin, N. G., de Geus, E. J., van Beijsterveldt, C. E., … & Kovas, Y. (2010). The heritability of general cognitive ability increases linearly from childhood to young adulthood. Molecular psychiatry, 15(11), 1112-1120.
  13. ↑ Jensen, A. (1969). How Much Can We Boost IQ and Scholastic Achievement. Harvard Educational Review.
  14. ↑ Protzko, J. (2015). The environment in raising early intelligence: A meta-analysis of the fadeout effect. Intelligence.
  15. ↑ Jensen, A. (1973). Educability and Group Differences. Harper & Row.
  16. ↑ McGue, M., Bouchard Jr, T. J., Iacono, W. G., & Lykken, D. T. (1993). Behavioral genetics of cognitive ability: A life-span perspective.
  17. ↑ Bouchard Jr, T. J., & McGue, M. (2003). Genetic and environmental influences on human psychological differences. Journal of neurobiology.
  18. ↑ Bamshad, M. J., Wooding, S., Watkins, W. S., Ostler, C. T., Batzer, M. A., & Jorde, L. B. (2003). Human population genetic structure and inference of group membership. The American Journal of Human Genetics, 72(3), 578-589.
  19. ↑ Guo, G., Fu, Y., Lee, H., Cai, T., Harris, K. M., & Li, Y. (2014). Genetic bio-ancestry and social construction of racial classification in social surveys in the contemporary United States. Demography, 51(1), 141-172.
  20. ↑ Jensen, A. R., & McGurk, F. C. (1987). Black-white bias in ‘cultural’ and ‘noncultural’ test items. Personality and individual differences, 8(3), 295-301.
  21. ↑ Weinberg, R. A., Scarr, S., & Waldman, I. D. (1992). The Minnesota Transracial Adoption Study: A follow-up of IQ test performance at adolescence. Intelligence, 16(1), 117-135.
  22. ↑ Sternberg, R. (2000) Handbook of Intelligence.
  23. ↑ Stricker, L. J., & Ward, W. C. (2004). Stereotype Threat, Inquiring About Test Takers’ Ethnicity and Gender, and Standardized Test Performance. Journal of Applied Social Psychology, 34(4), 665-693.
  24. ↑ Jensen, A. (1973). Educability and Group Differences. Harper & Row.
  25. ↑ Jensen, A. (1973). Educability and Group Differences. Harper & Row.
  26. ↑ Piffer, D. (2019). Evidence for recent polygenic selection on educational attainment and intelligence inferred from Gwas hits: A replication of previous findings using recent data. Psych.
  27. ↑ Kirkegaard, E. O., & Fuerst, J. G. (2023). A Multimodal MRI-based Predictor of Intelligence and Its Relation to Race/Ethnicity. Mankind Quarterly, 63(3).
  28. ↑ Lasker, J., Pesta, B. J., Fuerst, J. G., & Kirkegaard, E. O. (2019). Global ancestry and cognitive ability. Psych, 1(1), 431-459.
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