12.2 and 11.7 points below white adoptees at ages 7 and 17; however, with confidence intervals on the order of ±3 points, these should be taken as rough estimates. Thomas believes that the black-white gap may be explained by differences in pre-adoption environment and age at adoption. See also Interracial adoption Twin study Eyferth study Heritability of IQ Race and intelligence References Jensen, A. R. (1998). The g factor. Westport, CT: Praeger. Race and intelligence controversy Adoption research