Blacks score about 1 standard deviation below whites on IQ tests such as the WISC and the Stanford-Binet, and those tests are not "biased" in the sense of underpredicting minority student academic achievement. Hispanics score about 2/3 of a standard deviation below whites, and East Asians about 1/3 of an s.d. above. Intelligence is positively correlated with family income, because smart people tend to earn more money, and intelligence is highly heritable.
And there are studies using twins, adoption, and intermarriage that show that black and hispanic kids raised in white homes have the same or better IQ as the white population.
http://www.huppi.com/kangaroo/L-IQgapgenetic.htmMathematically, there are two main problems I see with the race-IQ issue.
The existence of the Flynn Effect contradicts these results. If the IQ ratios between the races were fixed, and IQ is mostly innate, then you could not have a steady increase in IQ across all races. You should see much smaller increases than we do for blacks and hispanics.
And when you look at the distribution of National Merit Scholars, the presence of minorities in the list does not match what you would expect using normal distributions. There are very, very few blacks and hispanics when you would expect a greater presence due to just raw random distribution.
There are some hidden variables and those are nutrition, schools, and parenting - mostly expectations.
Here are the excerpts from the link above:
Psychologist Richard Nisbett has been generous enough to provide the public with the details of all seven studies: (2)
After World War II, many American GI's (both white and black) fathered children by German women; these children were then raised in German society. The children fathered by black GI's had an average IQ of 96.5, and the children fathered by white GI's had an average IQ of 97 -- a statistically insignificant difference. (3)
In another study of children raised in residential institutions, black, white and racially mixed children who were raised in the same enriched environment were given IQ tests. At four years of age, the white children had an average IQ of 103, the blacks had an average IQ of 108, and the racially mixed children had an average IQ of 106. (4)
Another study measured the IQ's of children from black-white unions. Assuming that mothers are more important than fathers in the education and socialization of their children, the study sought to see if a child's IQ is higher when the white partner is the mother. This turned out to be true -- the IQ of a racially mixed child averages 9 points higher when it is the mother who is white. (5)
A genetic study took advantage of the fact that African-Americans genes are about 20-30 percent European, and that Africans and Europeans differ just enough in their genetic blood groups to determine the degree of "Europeanness" in an individual. If intelligence were indeed genetic and favored in Europeans, we might expect blacks with greater Europeanness to be more intelligent. However, a study of 288 young blacks found almost no relationship between Europeanness and intelligence: the correlation was a trivial and nonsignificant .05. (6)
Another genetic study examined the correlation between IQ and European blood groups (as opposed to the estimated Europeanness of individuals based on blood groups). In one sample of blacks, the correlation was a trivial .01, in the other a nonsignificant -.38, with higher IQ being associated with the more African blood groups. (7)
Another study tested the hypothesis that if IQ were both hereditary and favored in Europeans, then blacks with high IQs should have several times the level of Europeanness than the black population in general. But a study of high-IQ black children in Chicago found that this wasn't the case; in fact, these black children were slightly less likely to have European ancestors. (8)
