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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 of genetics in intelligence indeed varies with socioeconomic status—at least in the United States. The data reveal no such pattern in other parts of the developed world, a finding the researchers attribute to “more uniform access” to social programs such as strong education and health care.
In the American samples, researchers Tucker-Drob and Bates found a significant “gene-by-socioeconomic status” effect—meaning the genetic influence on IQ scores and achievement varied with social class. In the non-U.S. samples, the researchers found no significant interaction between genes and socioeconomic status for intelligence outcomes.The source of the geographical gap might come down to the different types of social programs employed in the U.S. and other parts of the world—specifically those related to literacy, school quality, medical access, income, and upward mobility.
Tucker-Drob says he believes the results reflect social disadvantage, not race or ethnicity, because previous work has reached similar conclusions in “racially homogenous samples.” In other words, even when race is held constant, being poor seems to stifle genetic variation on intelligence.
These results are just the latest scientific insight into how poverty alters the brain. Lab and field tests have found that scarcity imposes huge strains on mental resources, measured at a drop of 13 IQ points. Imaging studies, meanwhile, have revealed a link between income and the surface area of neural regions related to language and executive functioning in children. The new work tracks longer-term influences—but reaches similarly disturbing conclusions.
Read the full article at the link below.
Category(s):Child Development
Source material from City Lab
