Poverty's Role in Intellectual Development

Whether intelligence is more the product of nature or nurture has long fascinated American social scientists and the general public alike. Typically the result is explained as some balance of genetics and environment, but since the early 1970s, researchers have noticed that this scale tends to shift dramatically across social classes. It’s as if nature and nurture play by different rules for rich and poor.

Generally speaking this work has found that genetic variance tends to explain the bulk of IQ scores for advantaged groups, whereas environmental variance plays a larger role for disadvantaged ones. (This line of research draws its results from comparative analyses of identical twins, who share a complete genetic makeup, and fraternal twins or siblings.) In other words, when it comes to intelligence, a comfortable upbringing seems to help nature reach its potential, but an impoverished one seems to interfere at every turn.

Still, other studies have failed to confirm these findings, enough so that scholars continue to wonder. But a strong new analysis published in the journal Psychological Science suggests that the role...