"[M]ore intelligent Americans are more likely to prefer instrumental music such as big band, classical and easy listening than less-intelligent Americans." [...] "On the other extreme, as suspected, preference for rap music is significantly negatively correlated with intelligence. However, preference for gospel music is even more strongly negatively correlated with it."
The study "Why More Intelligent Individuals like Classical Music," by Satoshi Kanazawa [author of the study linking liberalism and atheism to IQ] and Kaja Perina, is forthcoming from the Journal of Behavioral Decision Making. The study's abstract observed the following:
Recent work on the evolution of music suggests that music in its evolutionary origin was always vocal and that purely instrumental music is evolutionarily novel. The Savanna-IQ Interaction Hypothesis would then imply that more intelligent individuals are more likely to prefer purely instrumental music than less intelligent individuals, but general intelligence has no effect on the preference for vocal music. [...] Additional analyses suggest that the effect of intelligence on musical preference is not a function of the cognitive complexity of music.
I have some speculation between the type of music that is conducive to one's occupation and the correlation between occupation and IQ.
From slaves in the fields to chain gangs in prison, manual labor has a long association with vocal music, which may perhaps carry over to the modern variants (pop, rock, country, R&B) that one might hear on an assembly line or at a construction site. I wonder if the lyrics of those genres might interfere with whiter-collar work that often employs language (scientists, engineers, technical workers, writers).
When I'm reading a technical manual, writing a procedural document, or juggling database tables, I gravitate toward instrumental music (Bach's Art of the Fugue, Brandenburg Concertos, cello suites, and the Well-Tempered Clavier; Beethoven's piano sonatas and string quartets; Mahler's symphonies; almost anything by Coltrane, Miles, Mingus, or Monk) and will shun most vocal music that I otherwise enjoy--but only if it's sung in English. I don't remember enough German for Schubert's lieder or Wagner's Ring to become distracting.
If simultaneous language tasks can overwhelm the brain's speech centers, could this lead to a preference for instrumental music?