Tuesday, May 20, 2008

IQ: interaction between race and age

In discussions of race and IQ, debate often focuses on a study of children fathered by soldiers stationed in Germany and then raised by German mothers (Eyferth 1961). The study found no significant difference in IQ between children with white fathers (83 subjects) and those with black fathers (98 subjects), the mean IQ being about 97 for both groups.

These findings are 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 years old. Since family socialization effects are stronger 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, 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.

I have doubts about the first criticism. Throwing in more environmental differences would make an innate difference less significant and harder to detect. But why would it disappear? It should do so only if the family environment were, on average, more conducive to learning in the biracial group. Both groups, however, had the same kind of family environment, i.e., a single German mother brought up the children. Am I missing something? I guess this is where the other two criticisms come in, i.e., the fathers were either North Africans or above-average African Americans.

But why, then, do we see similar IQ scores in children whose biological parents are clearly African-American and probably below-average ones at that? I am talking here of African-American children given up for adoption. At 7 years of age, Moore (1986) found a mean IQ of 117 among those placed in middle-class white families and a mean IQ of 104 among those placed in middle-class black families. These findings are criticized by Rushton and Jensen (2005), who argue that the children were raised in enriched environments and that the sample sizes were small (23 children in each case).

We see comparable findings, however, when IQ is measured with robust standardization samples of African-American and European-American children. When Dickens and Flynn (2006) analyzed the results of the 2002 standardization sample for the WISC (Wechsler Intelligence Scale for Children), they found that IQ starts off high in African American children and then declines with age:

African-American WISC scores
Age -- IQ
4 --- 95.5
12 -- 90.5
15 -- 88.8
24 -- 84.5

Dickens and Flynn (2006) also note that these scores show a gain of 5-6 points over the scores of black children thirty years earlier. But the decline of their IQ with age has remained stable. This decline also shows up in the Minnesota Transracial Adoption Study —a longitudinal study of black, biracial (black/white), and white children adopted into white middle-class Minnesota families (Scarr and Weinberg, 1976; Weinberg, Scarr, and Waldman, 1992). The children’s IQs were measured at 7 years of age and again ten years later:

------------------- Age 7 Age 17
Black children –---- 97 --- 89
Biracial children – 109 --- 99
White children –-- 112 -- 106

These findings parallel those of the Eyferth study. Young biracial children have IQ scores that are close to those of young white children. Even young black children have relatively high IQ. In this age group, interventions to raise IQ are successful. But the effects seem to wash out with age.

Rushton and Jensen (2005) are aware of this age trend, but they attribute it to the declining influence of family environments, i.e., at younger ages the diversity of learning environments within and between families accounts for a larger proportion of total IQ variability. This phenomenon would tend to obscure other sources of variability, thus making any black-white difference less significant. But why would it raise the IQ scores of black children while leaving those of white children unchanged? I suppose one might argue that family environments are more conducive to learning among African Americans than among European Americans. Is there any basis for such a belief?

In saying that this age decline is real, I’m not excluding an innate causation. Indeed, a socially induced causation seems less consistent with the data. It would have to affect even biracial children conceived by white mothers and raised by white parents in an overwhelmingly white cultural environment.

Among humans in general, intellectual capacity seems to decline with age. Indeed, there are statements in the literature that IQ declines from one’s twenties onwards (presumably among European Americans). Is this decline due to natural aging processes? Or is it prewired into the human organism?

Perhaps the ability to acquire new information becomes less useful with age and perhaps this was even truer in ancestral humans. What we call ‘intelligence’ may have originally been an infant trait that humans lost as they grew up. With the expansion of our cultural environment, natural selection would have progressively extended this infant trait into older age groups, and more so in some populations than in others.

By way of analogy, lactose tolerance was originally an infant trait and is still so in most human populations. It has become an adult trait in those populations that have long practiced dairy farming and adult consumption of milk.


Dickens, W.T., and J.R. Flynn. (2006). Black Americans reduce the racial IQ gap. Evidence from standardization samples. Psychological Science, 17, 913-920.

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

Moore, E.G.J. (1986). Family socialization and the IQ test performance of traditionally and transracially adopted Black children. Developmental Psychology, 22, 317-326.

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., Scar, 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...

Oh my. What an interesting concept.

Of course, you will be called a racist.

susanna said...

Years ago, I used to hear IQ defined as the ratio between "mental age" &
chronological age. Never was entirely sure what that meant, but whatever. Rushton claims that blacks mature earlier than whites & asians. So I'm wondering if some of the early higher IQ scores among blacks just reflect earlier maturation, rather than real intelligence.

Anonymous said...

Psychological Neoteny and higher education: associations with delayed parenthood

Anonymous said...

Jewish people are the most intelligent. They win almost 40% of the Nobel Prize's and they have a small population of only 14 million. So by far they exceed the other races in intelligence. The other races having huge numbers and such small contributions.

IQ tests, test intellectual conformity, not creativity and originality. This would explain the Asian high IQ's. They as a people are the ultimate conformists.

In IQ tests there is typically only one answer to the problem. That problem being a social conformity to reason. But everyone knows that Genius's and all the greatest developments in the world are not the product of conformity. Conformity never breeds creativity. We can see this in the lack of influence the Asian population has had on Science. China used to be called the "sick man" of Asia. Their population is massive and their contribution to innovation is almost nil. We can see this lack of originality in their adoptation of European philosophies, I.e. Communism.

Friedrich Nietzsche and other Philosophers have critized Asians. Nietsche used the words "Pallid osification" to describe Orientals.

Pallid: lacking sparkle or liveliness, dull.

Osification: Process of becoming inflexible: the process of becoming set and inflexible in behavior, attitudes, and actions. Inflexible conformity: rigid, unthinking acceptance of social conventions.

The reality is Asian people have yet to understand that laws and rules are arbitrary. Europeans make the rules and Asian's follow them.

It also doesn't make sense that Asian's are considered smart because of the fact that they have destroyed their own countries. This is due to over-population and their basic lack of enviromental understanding.

It is also common scientific fact that women who have many children are ignorant, and those who have less children are more intelligent. This has already been proven in studies. So it seems strange to say that Asians are smart when the obviousness of their backwards countries, and medieval lifestyle makes them contrary to that premise.

Europeans have the most advanced civilizations and every other race has yet to meet these levels other than the Japanese. The Japanese only being good at copying other people's inventions and making them better. Other than that their original creativity is lacking as well. They took American cars and made them better. They took the German camera and made it better. And they took German steel and made it better. Otherwise the greatest advances still come from Europeans and Jews. Other than that the Orientals have yet to produce an Einstein or a Thomas Edison.

When it comes to Black people. It makes sense that they have low intellectual comformity, I.e. IQ tests. They are far too creative to be trapped in this unoriginal form of conditioning. You can tell their creative capacity in their athletics, music, dance, and the way they talk. They by far exceed the Asiatic races in these areas. Being better singers, musicians ect. Blacks far exceed Asians in emotive expression. In all of North America there is only one or two famous high-paid Asian actors.

Reality, Europeans rule the world and they have allowed others to exist only out of desire for economic bennifet. They, (Europeans) are also the physically strongest, winning the Strongest Man competitions again and again. And they have become the most effective hunters due to their neccesity for animal food stuffs in a northern climate with lack of vegetables.

The greater the conformity, the weaker the race. Thus we see the races as they are today. The wild animal being bred out of man, and the physically impotent, conformist thriving.

Otherwise "Group psychology" is the most destructive thing in the world. All these stereotypes are false when it comes to the individual. Individualism is the most important thing for this time. All countries, Relgions, groups need to dissolve for man to live in peace.

Anonymous said...

I am an African American with an IQ in the 140s. My younger brother also has an IQ in the 140s, and we both got almost the exact same score on the SAT. Both of our parents have graduate degrees and both of our parents are Black.

As a Black person with a high IQ, I am frustrated by the lack of attention to the fact that we -- Black people with high IQs -- even exist. There are many of us, and statements that identify Jewish people or Asian people or white people as the most intelligent ignore the wide range of IQs that exist within ethnic groups.

I believe that my brother and I have such high IQs because my parents deliberately set out to raise us in cognitively rich environments that would enhance our abstract and critical thinking skills. They happen to have been extremely successful.

I don't believe that your blog post is racist, but I do resent that yours (like most internet discussions of IQ) paints each ethnic group with a broad and inaccurate brush.

Anonymous said...

Your statements regarding black people is called positive racism, if I am not mistaken. Let those blacks be athletes, singers and actors, leave science to the Jews and whites, and dull copying to the Asians :D

Anonymous said...

This is the very hottest of potatoes.

"A man that should call everything by its right name, would hardly pass the streets without beeing knock'd down as a common Enemy" -Halifax

Anonymous said...

"What we call 'intelligence' may originaly have been an infant trait that humans lost as they grew up... more so in some...than in others"

Speaking of individuals within a group and
of 'biological' maturity (rather than responsible social behaviour), early devlopers seem rarely to overlap with the most intelligent.

Anonymous said...

Screw you EC! You're so full of BS. And you definitely sound racist and as though you have something against Asians and Asian Americans. Rather, you don't sound racist. You ARE. I'm not trying to say any one group, Asian or non-asian is smarter than any other. I am, however, a PhD student studying giftedness, and I do think that there are different kinds of intelligence, and some (much) of it is culturally derived. Western and European cultures do more linear logical thinking, which we Americans are used to...including Asian AMERICANS (not from Asia)--which would point to a cultural influence in how you think. I read somewhere that many asian cultures do what is called "Circular" thinking. There are definite cultural differences.

Dan tdaxp said...

I love the theory that IQ may be an infantile trait extended in some populations [1], but then why do other traits (such as personality and political orientation) increase in heritability in the same way?

[1] http://www.tdaxp.com/archive/2008/12/03/the-recent-origins-of-black-female-hostility-to-miscegenation.html#comment-199221

Anonymous said...

All three groups dropped about 1o points. This simply implies that the IQ tests are overcompensating for age adjustments.

Another thing you have not considered is maternal health. Black mothers are probably less healthy than German mothers, especially black mothers who give their children up.

I think that the black/white IQ gap is largely due to these two effects: low socioeconomic status, and consequential low birth weight.
Factor in low Vitimin D levels - a known cause of low birth weight and a common problem among dark skinned people in cold climates, and you have just blown a giant hole in this theory.

If the age decline was steeper in black children, you might have been on to something, but it seems that the rate of decline is approximately equal in all groups. I am a bit surprised that the decline is greater in whites, but if it is true that environmental factors play a greater role at young ages, then it would make sense. Is the difference between 9 and 12 points statistically significant?

Anonymous said...

I am also a black person with a MENS-level I.Q., but I have learned that cognitive ability makes little difference in the real world. The effect of conformity is far more powerful. For instance, Catholics tend to have lower I.Q.'s than Protestants, but in my high school, all the fair Protestant boys with potential had Sicilian girlfriends! Hmmm--maybe the Moors' history of raping countless European mainlanders had something to do with this. I also mainly attract low-I.Q. black males and fit in with low-I.Q. black social groups, so in the end, my intelligence counts for absolutely nothing! (Neither does the fact that my father, who has a much higher I.Q. than I do, is white. I resemble my mother).

Chuck said...

I would like to see the Eyferth data. I don't see why the study is thought to provide strong support for the environmental hypothesis. (e.g Wicherts 2005: "In the author's view, Flynn's exhaustive 1980 analysis of Eyferth's work provides close to definitive evidence that the black disadvantage is not genetic to any important degree.")

Here would be my logic: Since the within race heritability of IQ is roughly 0.4 at age 10, the medium age of the kids in the study, the cognitive environment of the white kids would have to be equal to an IQ of 95.3 to drag the White IQ to 97.2. We can assume this is also the cognitive environment of the halfricans.

Assuming no range restriction or assortative mating and discounting the North Africans, the IQs of the Black-White kids as predicted by the genetic hypothesis would be: (91.75 X .4 + 95.3 X .6 =) 93.9 as opposed to 96.5 -- assuming you grant that the between race heritability of IQ acts in the manner of the within race heritabiliy and increases with age. Factoring in range restriction and assortative mating (with regression towards to mean) the IQ as predicted by the genetic hypothesis would be 95.5. So the genetic hypothesis predicts about as well (-1) as the environmental hypothesis (-.8).

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