Intelligence is influenced by not few, but many genes, according to a recent study from Harvard U., Cornell U. and Union College.
Over the years, many studies have linked particular genes to differences in intelligence, said Christopher Chabris, a researcher of the study and professor at Union College, in an email.
These studies showed that people with a version of a particular gene tend to score a bit higher on IQ tests than people without that version, he said.
“Initially, we thought that we would replicate those results – that is, we thought we would find the same associations that those earlier researchers found,” Chabris said. “But over time, our experiences led us to think that the opposite might be true, that most of those findings might be false positives.”
The researchers systematically tested as many of these “IQ genes” as they could by using three large, independent datasets, Chabris said.
“Our study is consistent with many recent findings that show that complex traits like intelligence, personality and even height are influenced by probably hundreds or thousands of genes, each of which has a very tiny effect on the behavior,” he said.
Associate Professor Kimberly Saudino, director of the Boston U. Developmental Behavioral Genetics Laboratory, said the study does not disprove evidence from twin and adoption studies that showed differences in intellectual abilities is “to some extent” related to genes.
“What they are saying is that early attempts to identify specific genes have produced what looks to be false positives,” Saudino said in an email.
Chabris said there is definitely a strong genetic component to intelligence, but the study shows the actual story is more complex than previously thought.
He said social scientists should take into account this complexity in future research and not rely on studies of individual genes.
“The problem is that if thousands of genes each explain a tiny fraction of these differences, it will take huge studies with tens or hundreds of thousands of subjects to find them,” Chabris said.
Professor V. Scott Solberg, the associate dean for research at BU’s School of Education, said he stressed other factors that might play a role in understanding human intelligence.
“The common belief is that genes set the parameters for one’s potential but that reaching that potential occurs when one is exposed to quality developmental and learning opportunities,” Solberg said in an email.
He said the task of creating an environment in which youth could maximize their intellectual potential fell to educators.
Professor Hardin Coleman, the dean of BU’s School of Education, said he agreed with the necessity for creating a supportive environment. This study shows humans have more abstract ideas than actual data when it comes to human intelligence, he said.
“The best we can say is that we all have bio-genetics that need to be effectively nurtured in order for us to be effective students and citizens,” Coleman said in an email.
Coleman said there has been a disproportionate focus on genes when it comes to human intelligence, which has distracted academic institutions from the ways in which social organization may affect outcomes.
“I think that the presumed genetic link to intelligence has had an awful effect on education,” Coleman said. “We are organized around the assumption that the ‘able’ or ‘bright’ students will succeed so that failure is a function of a lack of motivation or ability.”
Chabris said while other factors such as education influences intelligence, genetics still account for much of the difference.
“Our own results found that about 47 percent of the differences among individuals in intelligence can be explained by genetic differences among those individuals,” he said.
Chabris said the study has implications for how research involving genetic links to human traits will be conducted in the short-term future.
He said this would involve much larger genetic data sets and scientists who will need to look for how genes might have a very small effect on intelligence.
“We need to understand intelligence better,” he said. “[We need] to get a better handle on the biology of cognitive differences so that we can look for genes associated with biological factors rather than just overall IQ scores.”