Previously, we established that skin color and intelligence are correlated in the NLSY97 sample as predicted by hereditarian theory. Continuing this investigation, we looked into how these variables go together within and between African American families in the same sample. In other words, we wanted to know if lighter-skinned individuals tend to be smarter than their darker-skinned siblings just as the average light-skinned black in the general population is smarter than the average dark-skinned black. 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
Some variables in the Add Health and the NLSY97 allow us to investigate the relationship of skin color with IQ and racial ancestry with IQ (AHPVT scores and ASVAB scores) among the US black population. Given the positive results, a question worth considering is whether or not skin color mediate the relationship between family ancestry and IQ.
The Cayman Islands is a British Overseas Territory. In global comparison, this tiny dependency ranks near the top in standard of living and per capita GDP (currently sandwiched between the U.S., Ireland, Japan and Iceland). Lynn and Vanhanen’s books include data for Bermuda—another Overseas Territory—but do not mention the Cayman Islands.
At least one psychologist has administered intelligence tests to Cayman Islands school children (1960 Curti ), and this forgotten study is noteworthy because it is also one of the relatively rare instances where black and white IQ scores have been compared outside of the United States, Britain, and South Africa. Continue reading
The meaning of a Jensen Effect on the Color Effect
Dalliard showed that IQ correlates with color in both the American Black and Hispanic populations (a color effect) and, importantly, that the IQ-color correlations are positively related to a subtest’s general intelligence loading (a Jensen effect). In short, he showed that there was a Jensen effect on the IQ color effect. This is significant for reasons elaborated elsewhere. Generally, if an IQ difference is strongly positively correlated with g – is g(+) – biological causation is implicated; alternatively, if an IQ difference is strongly negatively correlated with g – is g(-) – cultural causation is implicated. Here, “biological causation” refers to psychophysiological influences on mental states that do not act through sensory informational pathways, while “cultural causation” refers to psychophysiological influences on mental states that act through these pathways; as an example of the general biological versus cultural causal schema, with respect to personality, differences induced by pharmacological agents would be classed as “biological causal” while differences induced by psychotherapy would be classed as “cultural causal.” This schema, of course, isn’t perfect – but it has utility and is not infrequently employed in psychology.