Genetics may influence intelligence by contributing to the development of larger brains

Genetic variants associated with intelligence are also weakly related to brain volume, according to a new study published in Cerebral Cortex.

“I was particularly interested in this project because it combines two rapidly growing areas of research into cognitive ability,” said study author Maxwell L. Elliott of Duke University.

“First, we are rapidly learning more about how brain structure and function lead to individual differences in cognitive ability. Second, with ever-growing genetics studies called genome-wide association studies (GWAS), we are quickly learning a great deal about how genetics lead to individual differences in cognitive ability.”

“This project combines these two areas of research by testing whether genetic variants that are associated with cognitive ability predict larger brains (a brain phenotype that has long been associated with higher cognitive ability),” Elliott explained.

Scientists previously identified more than 1,200 genetic variants associated with how much schooling an individual completes. They used this information to create a “polygenic score,” which predicts a person’s educational attainment.

For their new study, the researchers analyzed genetic and brain imaging data from 7,965 individuals who participated in four large studies. The studies were conducted in the United Kingdom, New Zealand, and the United States.

Elliott and his colleagues found that participants with higher educational attainment polygenic scores tended to score higher on tests of cognitive performance and also tended to have larger brains.

“Genetic variants associated with cognitive ability are, weakly, linked to larger brains,” he remarked.

“The biggest caveat is that this study is only the tip of the iceberg. As our understanding of the genetic and brain architecture of intelligence is refined, our understanding of the ways in which genetics lead to individual differences in brain structure and function will continue to develop. Much more work is needed to better understand these relationships.”

“Our study was a meta-analysis of four different samples. We found that sample composition mattered. In particular, samples that were more representative of the general population had larger effect sizes,” Elliott told PsyPost.

“A challenge facing research on how genetics affect the brain is the lack of population-representative samples with available brain imaging data. Efforts to recruit more representative samples that reflect the full range of cognitive functioning in the population are needed.”

The study, “A Polygenic Score for Higher Educational Attainment is Associated with Larger Brains“, was authored by Maxwell L Elliott, Daniel W Belsky, Kevin Anderson, David L Corcoran, Tian Ge Annchen Knodt, Joseph A Prinz, Karen Sugden, Benjamin Williams, David Ireland, Richie Poulton, Avshalom Caspi, Avram Holmes, Terrie Moffitt, and Ahmad R Hariri.