if I remember the story correctly:
when my dad joined the army, he and a bunch of other recruits had to take an IQ test. the sole purpose--to determine if they could use whatever rifle it is the army uses.
just about everyone failed. reason? you don't make people take tests in noisy environments--that will lower scores. especially with IQ tests. there may have been some other things going on, but my memory of the story is hazy.
its safe to say that those same recruits could, in fact, properly use the army's main rifle.