If brought back to life, early humans might grasp "American Idol," but be stumped by Mahler's symphonies. That's because music began, evolutionarily speaking, with singing, and instrumental music arrived much later, along with bigger brains (according to one prevailing theory).

That assumption is what led researchers to conduct a studythat concluded that high-IQ people are drawn to classical music, lower-IQ folks to vocal music.

The researchers drew on the 1993 edition of the General Social Survey, conducted by the National Opinion Research Center, in Chicago. That year, participants were asked to rate their enjoyment of 18 musical genres on a one-to-five scale. Half also took a vocabulary test, which was converted to an IQ score.

After statistically correcting for socioeconomic factors, the researchers found that higher IQ did, in fact, predict a preference for instrumental over vocal music. (Take that, Pitchfork!) The researcher's "instrumental" genres were classical, big band, and easy listening—yet, oddly, not jazz. But the finding would have been stronger had jazz been classified as non-vocal, the authors said, given its highbrow audience.

Focusing exclusively on classical, the picture was clearer: Those who liked classical music very much had an average IQ of 107; those who had mixed feelings scored 101; and those who hated it scored 93.