The following chart shows the results of the WISC-IV (UK version) given to several small samples of South African children (circa 2013):
Black Africa’s Wechsler full-scale IQ
Of the six demographic groups tested, the one most representative of black Africa would likely be disadvantaged black Xhosa speakers (DBXS) and these had an average full-scale IQ of 77.08 (UK norms).
However this number is likely an overestimate because the UK WISC-IV was nine years old at the time this study was published. Although I believe the Flynn effect is overestimated because of the kaufman effect and other methodological problems, Weiss et al., 2015 were able to sidestep these issues and show that at least from the 2000s to the 2010s, WISC-IV IQ increased by 0.31 points per year in the U.S.. Assuming UK norms became inflated at the same rate, DBXS have an adjusted IQ of 74.
Of course I realize the absurdity of using a sample of just 12 kids to represent all of black Africa, but it’s so rare to get a non-elite sample of black Africans taking a test as indepth as the Wechsler that I have little choice.
Black African Matrix IQ
Because the verbal subtests of the Wechsler require cultural knowledge that many black Africans have not been exposed to, people might think they would do better on a culture reduced test like the Raven Progressive Matrices. Richard Lynn however cited a series of studies showing black Africans did even worse on the Raven, averaging an IQ no better than 70.
However Wicherts et al,, 2009 accused Lynn of cherry-picking studies and argued that the true average Raven IQ of black Africa was 80. It is therefore interesting to note that on the matrix reasoning subtest of the WISC-IV, DBXS averaged an IQ equivalent of 83 (79 after adjusting for the Flynn effect).
Does this mean Wicherts et al. were right and Lynn was wrong? Probably not. The matrix reasoning subtest on the Wechsler has a test-retest reliability of around 0.66, while the Raven’s might be as high as 0.95. Taking the square root of these values tells us that matrix reasoning correlates 0.81 with true score while the Raven correlates 0.975.
What this means is that if the true score IQ of black Africans on this type of test is 31 points below the UK mean set at 100, they’ll score 31(0.975) = 30 points lower on the Raven, but only 31(0.81) = 25 points lower on the matrix reasoning subtest. The observed subtest score of 79 is not far from this prediction.
How would black Africans score on a truly culture reduced test?
The Raven is often described as a culture reduced test, however given the huge Flynn effect it has shown in some countries, many people are skeptical. One source of cultural bias might be exposure to columns and rows in school and media.
In my opinion, the most culture fair “verbal” subtest on the Wechsler is Digit Span and the most culture fair performance subtest is Block Design. Unlike Matrix reasoning, Block Design is a concrete task that is considered fun, and its fast pace makes it less dependent on culturally acquired values like persistence, cognitive confidence and intellectual discipline.
Thus, it’s interesting to note that after Flynn effect adjustments, DBXS averaged IQ 86 on Digit Span and IQ 80 on Block Design. Given the moderate correlation between these subtests, that works out to a composite IQ of about 80 which I take as a rough estimate for the real intelligence of black Africa.
Note, real intelligence should not be confused with genomic intelligence. Rather, real intelligence refers to a valid measure of the cognitive phenotype, but in the case of black Africans, the genotype is likely higher since even scores on the most culturally reduced tests can be depressed by sub-optimum nutrition and disease.