Sunday, March 10, 2019

IQ of biracial children and adults

First snow in Minnesota (c. 1895), Robert Koehler. Biracial children have IQ scores halfway between those of white children and black children, even when they are conceived by white single mothers and adopted into middle-class white families in their first year of life.

You may have heard about the Minnesota Transracial Adoption Study. It was a longitudinal study of black, biracial, and white children adopted into white middle-class Minnesotan families, as well as the biological children of the same families (Levin, 1994; Lynn, 1994; Scarr and Weinberg, 1976; Weinberg, Scarr, and Waldman, 1992). IQ was measured when the adopted children were on average 7 years old and the biological children on average 10 years old. They were tested again ten years later. Between the two tests, all four groups declined in mean IQ. On both tests, however, the differences among the four groups remained unchanged, particularly the 15-point gap between black and white adoptees. 

The biracial children remained halfway between the black and white adoptees. Could this be due to the parental environment being likewise half and half? Well, no. All of them were raised by white parents, and they were adopted at an early age: 19 months on average for the white adoptees, 9 months for the biracial adoptees, and 32 months for the black adoptees. The last figure is emphasized by Scarr and Weinberg (1976) as a reason for the IQ gap between the black and white adoptees. 

Fine, but what about the IQ gap between the biracial and white adoptees? Almost all of the biracial children were adopted at a young age and born to white single mothers who had completed high school. From conception to adulthood they developed in a "white" environment. If anything, the white adoptees should have encountered more developmental problems because they were adopted at an older age.

Could color prejudice be a reason? Perhaps the biracial children were unconsciously treated worse than the white children. By the same reasoning, they may have been treated better than the black children. We can test the second half of this hypothesis. Twelve of the biracial children were wrongly thought by their adoptive parents to have two black parents. Nonetheless, they scored on average at the same level as the biracial children correctly classified by their adoptive parents (Scarr and Weinberg 1976).

The Eyferth study

Another study found no difference in IQ between white and biracial children. This was a study of children fathered by American soldiers in Germany and then raised by German mothers (Eyferth 1961). It found no significant difference in IQ between children with white fathers and children with black fathers. Both groups had a mean IQ of about 97.

These findings were criticized by Rushton and Jensen (2005) on three grounds:

1. 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 be needed to find a significant difference between the two groups.

2. Between 20 and 25% of the “black” fathers were actually North African.

3. At the time of the study, the US Army screened out low IQ applicants with its preinduction Army General Classification Test. The rejection rate was about 30% for African Americans and 3% for European Americans. African American soldiers are thus a biased sample of the African American population.

Another factor is that the capacity for intelligence seems to be more malleable in children than in adults. We see this with the Minnesota Transracial Adoption Study. In the enriched learning environment of middle-class Minnesota families, all of the children showed impressive IQ scores at 7 years of age. By 17 years of age, however, this benefit had largely washed out:

-------------------- Age 7 Age 17

Black children ----- 97 ----- 89

Biracial children - 109 ----- 99

White children --- 112 ---- 106

Does intelligence really decline with age because of wear and tear on the brain? Perhaps we’re programmed to be most intelligent in childhood. That’s when we have to familiarize ourselves with the world. The capacity for intelligence may then be gradually deactivated as we get older because it’s less necessary.

This deactivation may follow different trajectories in different human groups. In early Homo sapiens, it may have begun not long after puberty. As ancestral humans made the transition to farming, sedentary living, and increasingly complex societies, this learning capacity became more necessary in adulthood, with the result that natural selection favored those individuals who retained it at older ages. This gene-culture coevolution would have gone farther in some populations than in others.

The Fuerst et al study

A recent study led by John Fuerst has confirmed the intermediate IQ of biracial individuals, this time in adults. The research team used the General Social Survey, which includes not only ethnic, sociological, and demographic data but also a measure of intelligence (WordSum):

The relationship between biracial status, color, and crystallized intelligence was examined in a nationally representative sample of adult Black and White Americans. First, it was found that self-identifying biracial individuals, who were found to be intermediate in color and in self-reported ancestry, had intermediate levels of crystallized intelligence relative to self-identifying White (mostly European ancestry) and Black (mostly sub-Saharan African ancestry) Americans. The results were transformed to an IQ scale: White (M = 100.00, N = 7569), primarily White-biracial (M = 96.07, N = 43, primarily Black-biracial (M = 94.14 N = 50), and Black (M = 89.81, N = 1381).

The same study also found a significant negative correlation among African Americans between facial color and WordSum scores. The correlation was low (r = -0.102), but it would be difficult to get a higher correlation because of the measures used. Self-reported skin color correlates imperfectly with actual skin color, which in turn correlates imperfectly with European admixture. Wordsum likewise correlates imperfectly with IQ (r = 0.71). On a final note, the correlation between facial color and WordSum scores was not explained by region of residence, interviewer’s race, parental socioeconomic status, or individual educational attainment.


Eyferth, K. (1961). Leistungen verscheidener Gruppen von Besatzungskindern in Hamburg-Wechsler Intelligenztest für Kinder (HAWIK). Archiv für die gesamte Psychologie 113: 222-241.

Fuerst, J.G.R., R. Lynn, and E.O.W. Kirkegaard. (2019). The Effect of Biracial Status and Color on Crystallized Intelligence in the U.S.-Born African-European American Population. Psych 1(1): 44-54.

Levin, M. (1994). Comment on the Minnesota transracial adoption study. Intelligence 19: 13-20.

Lynn, R. (1994). Some reinterpretations of the Minnesota Transracial Adoption Study. Intelligence 19: 21-27.

Rushton, P. and A.R. Jensen. (2005). Thirty years of research on race differences in cognitive ability. Psychology, Public Policy, and Law 11: 235-294.

Scarr, S., and Weinberg, R.A. (1976). IQ test performance of Black children adopted by White families. American Psychologist 31: 726-739.

Weinberg, R.A., Scarr, S., and Waldman, I.D. (1992). The Minnesota Transracial Adoption Study: A follow-up of IQ test performance at adolescence. Intelligence 16: 117-135.


Anonymous said...

It's interesting that vast majority of inventions/discoveries were done by those from Cro-Magnon lineage(Europeans/Euro-Americans}.So Cro-Magnons were gifted with a mutation(s) that could be considered as intelligence genes.

Sean said...

No evidence of an advantage for children with a white mother and black father over the other way about then?

Oprah-me said...

''It's interesting that vast majority of inventions/discoveries were done by those from Cro-Magnon lineage(Europeans/Euro-Americans}.So Cro-Magnons were gifted with a mutation(s) that could be considered as intelligence genes''

A tiny minority, majority of whitey is not quite bright...

Anonymiss said...

Interestingly, IQ results are very different for black and half-black Brits and black Bermudians (Robert Lindsay talks about this on greater detail). Studies also show that when Canadians (all races) are tested at American norms rather than Canadian ones, they perform much higher and score higher than American youth. It is perhaps time to consider that there is something unique about American living and culture that depresses IQs below the norms in other first-world economies.

Peter Frost said...


I've seen studies that show rising IQ in "black" British students. A major reason is that a growing proportion of "blacks" in Britain are biracial children who prefer to self-identify as "black." Similarly, a growing proportion of "biracials" are children who are only 1/4 of African descent.

I've also seen British studies that show high IQ and high academic performance among Igbo children. I'm not surprised.

Perhaps it's also time to question the assumption that the term "white" covers a fixed, unvarying reality. A genetic marker for empathy has a higher incidence in “Canadian Caucasians” (50%) than in "American Caucasians” (31-37%). This may reflect differences in participant recruitment or in ethnic mix between the two countries.

ChristopherDT said...

Pardon me for putting an unrelated question in this comments section. I haven't seen a general contact for you, so this seemed as good as anything.

Recently I have been trying to determine the validity of the idea that increasing mutational load is a factor (or the primary factor) in lowing Western IQ and raising rates of psychological illness, among other dysgenic affects. I suspect you are familiar with the thesis, but allow me to repeat it so we are on the same footing. Previous to the industrial revolution child mortality was at greater than 40%. This mortality was a strong filter for pernicious mutations. Post industrial revolution this filter has been lost and mutations are accumulating generation to generation. Proponents of the theory are Bruce G. Charlton, Edward Dutton and Michael A. Woodley. See this post by Charlton for more complete summary than I have provided:

My essential concern, other than a simple pursuit of whatever might be true, is that the mutational load theory is monumentally more pessimistic in terms of what it views as necessary to maintain a high functioning population, or even to avoid progressively dysgenic effects. I would be very interested if you have any thoughts on this subject or might suggest any sources you view as definitive. Thank you for your time.

Sean said...

To migrate (legally or otherwise) from a Third World country to Britain is costly; the people who make that journey are relatively rich not poor in their own countries. As a Third World country gets wealthier, more of their population can afford to immigrate, and as Diaspora communities in the West increase there will be relatives already in the Western destination to assist the newly arriving immigrants, thus requiring less and less of an investment to migrate. In the aforementioned way, immigration into the West has an inherent tendency to progressively poorer and lower IQ immigrants. There is also negative assimilation, whereby the second generation of immigrants do worse than their IQ would predict, due to being brought up in a more progressive cultural environment than they are genetically co-evolved with.

Don Pepe said...

Why did your most recent article on Unz Review disappear?

Peter Frost said...


Yes, I addressed that issue in one of my posts:

The Kong et al. (2017) study strongly suggests that the genetic capacity for intelligence is declining in the Western world independently of ethnic change. One explanation is that deleterious mutations are no longer being weeded out. Another is differences in fertility between social classes, or simply between fast-life-history and slow-life-history individuals, although Iceland is not as class-stratified as other Western countries.

Kong, A., M.L. Frigge, G. Thorleifsson, H. Stefansson, A.I. Young, F. Zink, G.A. Jonsdottir, A. Okbay, P. Sulem, G. Masson, D.F. Gudbjartsson, A. Helgason, G. Bjornsdottir, U. Thorsteinsdottir, and K. Stefansson. (2017). Selection against variants in the genome associated with educational attainment. Proceedings of the National Academy of Sciences 114(5): E727-E732.


I understand your argument, but I'm not sure that immigrants were necessarily better in the past because of the relatatively higher cost of transport. A stronger factor was probably the lack of social welfare programs. I read somewhere that a quarter of Italian immigrants to the U.S. had to go home because they couldn't make a go of things in their new country.


To the best of my knowledge, my last article at The Unz Review appeared on April 4, 2016 "Farewell to Henry". He asked me to come back a few months ago, but the issue of comment moderation seems to be insurmountable. Another issue is Greg Cochran, i.e., my discomfort with Unz's vendetta against him.

N. said...

What's pernicious about your opinions Frost is your insistence that IQ has much validity, if any, as an indicator of the qualities needed to survive under our current milieu, which are ever-changing. I have yet to see any adequate evidence supporting your (biased) speculation

You seem to rely on genetic essentialist, androcentric and eurocentric biases that are increasingly being challenged nowadays, esp. by marginalized groups who are gaining power.

You mention that lack of welfare programs are a factor in the retention of immigrants but these poor, uneducated people's labor was needed at the time as well. These generational poor (whose poverty is no fault of their own, see: the disparity in college admissions and opportunities between the classes) who have occupied some of the lower divisions of labor are now losing their jobs to automation and outsourcing to hyper-exploited foreign workers. We're not living in a meritocracy, Frost. We're under the tyranny of the likes of you: egocentric, psychopathic males who would rather society crumble than abandon their notion of a natural supremacy.

Look at the people who follow your blog, why are so many of your fanboys white supremashits
Frost? Do you find this incidental?

Sean said...

Unz was a generous patron and continues to be a gracous host to GC comments despite his recent mocking references to Ron at West Hunter. He banned me from West Hunter, which is fair enough because it is his site and his rules. I get the impression though, that GC is more my way or the highway than RU.

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