Scientists who hunt for "intelligence genes" used to think there were fewer than half a dozen of them. But in recent years, they determined there may be at least 1,000—each with just a tiny effect on the differences in people's IQ. A study released today found new evidence that many genes play a role in intelligence, but scientists still couldn't pinpoint the specific genes involved, Molecular Psychiatry reports.
Scientists have come to realize that many genes work together to shape intelligence much like the different instruments of an orchestra that play in sync. Unless there's a soloist playing, it's often difficult to decipher the contributions of individual instruments. The new DNA study came to similar conclusions. Researchers didn't ID any genes affecting IQ, but they estimated that they found a genetic influence that accounts for at least 40% to 50% of the differences on intelligence test scores in the 3,511 unrelated adults in their study who were tested on knowledge and problem-solving skills.