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Researchers have found that three genetic variants in humans can account for a couple of IQ points, according to a new study. 

Intelligence, cognitive ability or cognitive performance is measured by a series of tests, that aim to quantify skills such as memory and analytical ability. However, a measure of 'intelligence' has been controversial and hence cognitive performance scores are widely used. 

The study in question, compared the cognitive performance between family members including comparisons between identical and no-identical twins. Eventually, researchers were able to quantify the contribution if genetic and environmental causes of individual differences. 

Previously, using a genome-wide study in a sample of 18,000 individuals, we could not identify a single genetic variant associated with cognitive performance. Using the new proxy strategy, though, we identified three genetic variants associated with cognitive performance. As expected from the calculation, the effects of these variants on cognitive performance are tiny, the press release added.

Researchers also underscored the fact that a copy of each variant accounts only 0.3 points on a standard IQ test. A person who inherits all six copies (note: one genetic variant has two copies) of increasing variants differs by 1.8 points compared to individual who inherits none, which is a very small difference. 

The study is published in the Proceedings of the National Academy of Science (PNAS).