It’s complicated
A gene called COMT has a mutation that is associated with better working memory and higher verbal IQ in those that possess two copies of it, compared with those who have only one copy of it or two copies of a different mutation. However, the mutation is also associated with emotional vulnerability and anxiety. In a recent study of about 800 Taiwanese students who took a high-stakes assessment exam that has a significant effect on their future education, those with two copies of the mutated gene scored lower than others, despite its effects on working memory and verbal IQ. This may indicate that the down side of the mutation outweighs the up side—at least in that particular population and those particular circumstances. This article from New Scientist has the details. Note that the sample size is rather small for such studies, so it’s not clear what exactly is going on. However, this does seem to make the point that pinpointing the effect of single genes on cognitive performance is a subtle business.
