One of the studies conducted by Scarr and Weinberg in 1976 explains how genetic inheritance may influence one behaviour. They focused on parents who had raised both natural and adopted children. The assumption was that all children will have similar behaviour/characteristics, having the same upbringing, and being raised in the same environment, with the same parents. Any significant differences between parent-child IQ correlations for adopted and natural children were attributed to genes.
Trans-racial adoption participants who were African American children adopted by middleclass White
Trans-racial adoption participants who were African American children adopted by middleclass White