Question

It is often difficult to separate the relative influences of heredity and environment on human characteristics. People who have similar genetic makeup (e.g., brothers and sisters, parents and their children) typically live in similar environments as well. So when we see similarities in IQ among members of the same family, it is hard to know whether those similarities are due to the genes or to the environments that family members share. Nevertheless, a significant body of research tells us that both heredity and environment affect intelligence.