[9급 지방직 영어 2019년 19번]

Language proper is itself double-layered. Single noises are only occasionally meaningful: mostly, the various speech sounds convey coherent messages only when combined into an overlapping chain, like different colors of ice-cream melting into one another. In birdsong also, ________________________________________: the sequence is what matters. In both humans and birds, control of this specialized sound-system is exercised by one half of the brain, normally the left half, and the system is learned relatively early in life. And just as many human languages have dialects, so do some bird species: in California, the white-crowned sparrow has songs so different from area to area that Californians can supposedly tell where they are in the state by listening to these sparrows.