In a breakthrough, a team of geneticists from Europe and the US said Monday that they had linked 52 genes to intelligence in almost 80,000 people.  The 52 genes do not, alone, determine intelligence – the researchers said their combined influence was still tiny, which suggests that thousands more have yet to be discovered. Environmental factors are also considered key to shaping individual intelligence.

However, the discovery could lay a foundation on which to build experiments exploring the genetic basis for intelligence, reasoning, and problem-solving, according to experts. They could even help scientists looking for new interventions to help children with difficulties learning.

University of Texas psychologist Paige Harden, who was not involved in the research, praised the study, saying it “represents an enormous success.”

Historically, psychologists have tested for intelligence using questions and exams. The tests investigate different areas of intelligence, such as memorization or verbal reasoning. Though subjects score differently in each area, individuals tend to score similarly in the various areas, with similar low or high scores in each. Neurologists have long investigated what accounts for this variation in intelligence, finding some correlation with brain size and the ability of brains to send signals from one region to others.

Danielle Posthuma, a geneticist at Vrije University Amsterdam is the senior author of the new paper.

She said:

“I’ve always been intrigued by how it works. Is it a matter of connections in the brain, or neurotransmitters that aren’t sufficient?”

Her research, and many other studies, had found there was some genetic basis for intelligence. Advances in DNA sequencing technology paved the way for recent research, which looked for shared genetic markers in individuals with high intelligence test scores. However, the first wave of this research yielded few answers. Intelligence tests take time to complete, making it difficult to do a single large scale study.

In the new research, Posthuma and other researchers merged data from 13 earlier studies, creating a massive database of genetic markers and intelligence test scores. After years of fruitless research, Posthuma was surprised when the results turned up 52 genes with strong links to intelligence.

Still, these genes together only account for a tiny percentage of the variation in intelligence, with each genetic variant only lowering or raising the score by a fraction of a point.

“It means there’s a long way to go, and there are going to be a lot of other genes that are going to be important,” according to Posthuma.

Studies such as this one do not indicate that intelligence is a fixed from birth, determined only by genetic variation. Environment is still considered to be a key factor. But the new information will help better determine ways to help children learn – a knowledge of the genetic variations could help scientists determine how effective various learning strategies could be for different individuals.

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