It’s been almost 50 years now that the famous study of Willerman et al. (1974) has been published. This study is regularly cited as one of the most convincing evidence against the hereditarian hypothesis, despite strong emphasis by hereditarians on the failure of experimental efforts to raise IQ (more specifically, g) and population differences magnifying during adolescence or adulthood due to increasing heritability with age (Jensen, 1998, pp. 333-344, 359, 474; See Malloy  for a case of a stability model with respect to the Black-White gap). Caution about this study is now vindicated. The data used by Willerman also revealed a pattern: the IQ deficits related to having a Black mother seem to vanish over time (Hu, 2022). Continue reading
An early version of this paper was posted on June 25th. The paper has since been extensively edited and corrected and, subsequently, published at Open Differential Psychology on July 25/26th, 2014. The paper and data files can be found here at the Open Differential Psychology site.
Cognitive ability differences between racial/ethnic groups are of interest to social scientists and policy makers. In many discussions of group differences, racial/ethnic groups are treated as monolithic wholes. However, subpopulations within these broad categories need not perform as the racial/ethnic groups do on average. Such subpopulation differences potentially have theoretical import when it comes to causal explanations of racial/ethnic differentials. As no meta-analysis has previously been conducted on the topic, we investigated the magnitude of racial/ethnic differences by migrant generations (first, second, and third+). We conducted an exploratory meta-analysis using 18 samples for which we were able to decompose scores by sociologically defined race/ethnicity and immigrant generation. For Blacks and Whites of the same generation, the first, second, and third+ generation B/W d-values were 0.79, 0.79, and 1.00. For Hispanics and Whites of the same generation, the first, second, and third+ generation H/W d-values were 0.76, 0.67, and 0.57. For Asians and Whites of the same generation, the first, second, and third+ generation d-values were -0.08, -0.21, and 0.00. Relative to third+ generation Whites, the average d-values were 0.99, 0.84, and 1.00 for first, second, and third+ generation Black individuals, 1.04, 0.71, and 0.57 for first, second, and third+ generation Hispanic individuals, 0.16, -0.18, and -0.01 for first, second, and third+ generation Asian individuals, and 0.24 and 0.04 for first and second generation Whites.
Keywords: Immigrants, group differences, race, ethnicity, aptitude, National IQ
According to Spearman’s hypothesis, the magnitude of the black-white gap on a given cognitive ability test is primarily determined by the test’s g loading. Tests that are better measures of g are associated with larger gaps.
The Differential Ability Scales, Second Edition, or the DAS-II, is an IQ test for assessing children and adolescents. It comprises a total of 21 subtests, although in the present analysis only 13 subtests are used, because not all tests are administered across age groups. I will use the method of correlated vectors (MCV) to test whether g loadings are correlated with mean racial differences on the DAS-II subtests. In addition to the black-white gap, I will also investigate if the test performance of Asians and Hispanics is predicted by g loadings. Continue reading
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! Continue reading