Deep roots of admixture-related cognitive differences in the USA

Abstract

This study attempted to determine if the association between genetic admixture and cognitive ability among African, European, and Amerindian descent groups in the USA holds across a large time period. First, we used the large and nationally representative Adolescent Brain Cognitive Development Study (ABCD) sample to examine the association between cognitive ability and parental-reported race, genetically-predicted color, and genetic ancestry among Puerto Ricans, non-Hispanic Whites, Blacks, and American Indians in the 21st century. Second, we use the 1850 to 1930 US censuses to trace ancestry-associated cognitive differences back to the early 19th and early 20th century among African American, American Indian, and Puerto Rican groups by using age-heaping-based numeracy as a proxy for cognitive ability. In the ABCD sample, we found that European ancestry is positively associated with cognitive ability within race/ethnic groups. In the census data, among African Americans and American Indians but not Puerto Ricans, we find that greater apparent European admixture is associated with higher numeracy, and this holds when we subset by age, sex, and literacy status. Therefore, we established that admixture is associated with cognitive ability in the 21st century as it was in the 19th and early 20th century. The implications of these findings are discussed.