Genetic influence on intelligence varies with social class in the US but not in Australia and W. Europe

Genes have a strong influence on intelligence but this influence is found to vary with social class in the US, though that is not happening in Australia and Western Europe.

The findings are based on data gathered from 14 independent studies and are published in Psychological Science, a journal of the Association for Psychological Science.

Psychological scientists Elliot Tucker-Drob of the University of Texas at Austin and Timothy Bates at the University of Edinburgh conducted a meta-analysis to ascertain the link between genes and intelligence.

The researchers analyzed data from a total of 24,926 pairs of twins and siblings who had participated in studies conducted in the United States, Australia, England, Sweden, Germany, and the Netherlands. They found that the relationship between genes, socioeconomic status, and intelligence depended on which country the participants were from.

"The hypothesis that the genetic influence on intelligence depends on socioeconomic status was not supported in studies outside of the US," says Tucker-Drob. In fact, the Netherlands reported an opposite trend.

According to the research findings, differences between the US and other countries could be explained by differences in the impact of low socioeconomic status, in terms of healthcare and social welfare programs.

According to Bates, a primary question for future research will be to identify the specific aspects of a society that "break the link between social class and the expression of genetic potentials for intellectual development."

"Once such characteristics are identified, they could inform policies directed at narrowing test score gaps and promoting all of the positive consequences of higher IQ, such as health, wealth, and progress in science, art, and technology," Bates concludes in the study.

The study included participants that showed differences in their genetic relatedness (that is, siblings versus identical twins) to help the researchers separate the genetic and the environmental influences.

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