Gildea (1992): A lost IQ study of transracially adopted Koreans

In 2005 one of my co-bloggers at Gene Expression posted an excerpt from a Wall Street Journal article asserting that large US ethnic performance differences in spelling bees were due to dubious cultural values. My response was Is it Really Bee-cause of Culture?, which argued that cultural arguments for ethnic differences (at least in their standard formulations) are empirically false. First of all, it’s one thing to argue that “correlation does not imply causation”, but most claims about, say, Asian super-parents or black anti-intellectualism don’t even rely on real correlations, but ex post facto rationalizations: Asian parents must be amazing, because look at how well their kids perform! Research has disconfirmed many of these supposed ethnocultural advantages and disadvantages. Second, behavior geneticists have looked at full siblings, half siblings, adopted siblings, etc; even where real correlations between outcomes and home variables exist (e.g., children with high IQs come from homes with more books), these correlations are demonstrably the result of shared genetic background between parents and their biological offspring, not due to the influences of home environment. Third, and this will be my primary focus here, transracial adoption research is able to test these claims even more directly. Do people from ethnic group Y, that are raised by parents from ethnic group Z, grow up to become like people from biological group Y or from cultural group Z? Again this research has not been kind to culture theory. (“Culture”, of course, could also be transmitted through other hypothetical social influences, but it is not my intention to discuss this all in great detail right now).

Shortly after writing that post, I decided that more needed to be written about transracial adoption research as a behavior genetic experiment. Arthur Jensen, Richard Lynn, and J. Philippe Rushton have all cited the Minnesota Transracial Adoption Study, as well as several IQ studies of transracially adopted Asians, in support of the hereditarian position. And Richard Nisbett has referenced several other adoption studies that suggest no racial gaps. However, I suspected there was more data for transracially adopted children than what this small cadre of scientists had already discussed (at the very least for important variables other than intelligence); research that could give us a more complete picture of what these unusual children become, and what this can tell us about the causes of ethnic differences in socially valued outcomes.

So I spent a number of months during 2006 doing research for an E-book idea (tentatively titled Race Differences & Transracial Adoption). And there were indeed a number of novel and revealing finds in that process. Unfortunately—as usual—I could not obtain all the existing research I wanted, so I never proceeded with the project. Even worse, I never shared what I had discovered with a wider audience. Human Varieties can now serve as an appropriate platform to share those discoveries.

This post heralds the grand new epoch of sharing by summarizing an unpublished doctoral dissertation on IQ and academic achievement in a sample of transracially adopted Koreans (Gildea, 1992 ). According to Google Scholar, no one has previously cited this paper. Here be dragons!

Linda Gildea (1992 ) contacted families of transnationally adopted Koreans through an overseas adoption agency serving the New England area. The participating sample is 31 white American families with 43 adopted Korean children, ages 8-12. The average age of the children was 10.5 years old. They were all adopted between 1976-1980, and the data was collected from about mid 1989 to mid 1990. The average age of adoptive placement was 7 months; 74% were placed before 9 months and 94% were placed before two years. 83% of the children were girls. 74% of the fathers and 68% of the mothers were college graduates. 81% of the fathers and 55% of the mothers were professionals. Most were dual income households. Their median income was $50,000. (This is similar to the socioeconomic profile of parents in other adoption studies (pp. 116-117)).

These elementary school children were tested with the California Achievement Test (reading and mathematics) and the Wechlser Intelligence Scale for Children-Revised. They performed much better than average on these tests (p. 94). The average child scored at the 79th percentile on CAT reading, and at the 77th percentile on CAT mathematics. The table with the Wechsler IQ scores (p. 96) is reproduced below.

The Wechsler norms used for the raw score conversion were from 1974, so 5 points should be deducted from the full-scale IQ of 122 (!!) to account for 16 years of norm inflation. This leaves us with a not much less intimidating average IQ of 117 for 43 transracially adopted Korean children. The children scored slightly higher on Wechsler Verbal than Wechsler Performance, just as they scored slightly higher on CAT reading than CAT mathematics.

Gildea also reports the correlations between IQ, achievement, and home environment variables (pp. 105-113). Home learning environment was the only variable to have a significant correlation with mathematics achievement (p. 119), while WISC verbal scores were the only variable to have a significant correlation with reading achievement (p. 122). Heritability is lower in pre-adolescent children, so there are not as many null results for household influences at younger ages. However, parental education and occupational levels were still poor predictors of achievement, and socioeconomic status was actually negatively correlated with achievement scores (p. 120).

Gildea compares these children with other adopted samples of American children that were tested with Wechsler scales (pp. 123-124). The scores in these other studies ranged from 109-117, but these numbers would not be adjusted for norm inflation. Even so, the children in this study appear to have scored 1/3-1 SD higher than what is typically found for adopted children (the lower estimate more closely describes the IQ difference found between East Asians and whites). The author offers several standard “Occam’s butterknife” non-explanations for this: perhaps the children experienced racism and worked harder at being smart to overcome the hardship (p. 125); perhaps the parents and teachers had racialized beliefs about the children’s intellectual potential, and these expectations boosted the children’s IQ scores (p. 126). More plausibly, she also notes that this volunteer sample may have differed in some unknown aspects from the non-volunteers. But it is nowhere noted how many families were contacted, and how many did not participate. The author also prudently and tactfully offers the hereditarian possibility: that Korean genetic background was a contributing factor (pp. 128-130).

Few researchers have acknowledged that East Asians have higher intelligence than whites, much less the genetic explanation for said gap, so few critics have challenged these ideas on empirical grounds. An exception is Sue & Okazaki (1991), in an exchange with Richard Lynn in the American Psychologist. Sue & Okazaki reject evidence from one transracial adoption study of Koreans in Francophone Belgium (Frydman & Lynn, 1989) because the deviation IQs were calculated on norms from France. They reject evidence from another transracial adoption study of Asian-Americans (Winick et al., 1975) because it did not report home background variables or investigate their possible influence.

Here, at least, we have a transracial adoption study for Koreans that can’t be dismissed on these specific limitations.

In fact there are more adopted Korean IQ studies and more transracial adoption data from around the world. I will discuss this research here over time.



Frydman, M., & Lynn, R. (1989). The intelligence of Korean children adopted in Belgium. Personality & Individual Differences, 12, 1323-1325.

Gildea, L.A. (1992). The academic achievement of adopted Korean children: factors of intellect and home educational environment. Unpublished doctoral dissertation, Boston University, USA.

Lynn, R. ( 1991). The educational achievements of Asian Americans. American Psychologist, 46, 875-877.

Nisbett, R.E. (1998) Race, Genetics, and IQ. In C. Jencks and M. Phillips (Eds.), The Black-White Test Score Gap (pp. 85-102). Washington, D.C.: Brookings Institution Press.

Sue, S., & Okazaki, S. (1991). Explanations for Asian-American achievements: A reply. American Psychologist, 46, 878-880.

Winick, M., Meyer, K.K., & Harris, R.C. (1975). Malnutrition and environmental enrichment by early adoption. Science, 190, 173-1175.


  1. 117 is pretty high. Did the adoptive parents take any tests as part of the study?

  2. I find it interesting that the verbal scores weren’t relatively low compared to their other abilities. Theres been a bit of speculation on whether it is one of the North-East Asians relative cognitive weak points. The Belgium adoption study showed the Koreans scored the lowest on the Vocabulary sub-test.

  3. Nick Stockwin

    June 29, 2016 at 7:51 pm

    Most adopted Korean children are from orphanages where intellectually low performing parents abandon their babies. The samples are bound to show IQs lower than the average of Korean children, hence not to be compared with children from average White or Black families.

  4. As to the point that the children scored higher on the verbal section than in the math section of the tests, it might be due to the makeup of the group being heavily girl-skewed.

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