Deep roots of admixture-related cognitive differences in the USA?

Abstract

This study attempts to determine if the association between admixture and cognitive ability among African, European, and Amerindian descent groups in the USA holds across a large time period. First, we use the large and nationally representative Adolescent Brain Cognitive Development Study (ABCD) sample to examine the associations between cognitive ability, socially identified-race, genetically-predicted color, and genetic ancestry among Puerto Ricans, and non-Hispanic Whites, Blacks, and American Indians in the 21st century. Second, we use the 1850 to 1930 US censuses to see if we can trace ancestry-associated cognitive differences back to the 19th and early 20th century by taking advantage of early census distinctions by blood and also by using age-heaping based numeracy as a proxy for cognitive ability. In the ABCD sample, we find that European ancestry is positively associated with cognitive ability within race/ethnic groups (_r_s =.05 to.47; _r_weighted-average =.10). In the census data, among African Americans and American Indians but not among Puerto Ricans, we find that greater apparent European admixture is associated with higher numeracy and that this holds when we subset data by age, sex, and literacy-status. The implications of these findings are discussed.