Effects of part of speech: Primitive or derived from word frequency?

Part of speech (POS hereafter) is known to affect both duration and F0, such that, nouns are longer and higher in F0 than verbs. In this study we tested the hypothesis that the POS effects are actually a word frequency effect, and that this effect is predictable from information theory. We tested this hypothesis by comparing 44 phonologically matched noun-verb pairs in Mandarin. Results show that there were clear effects of word frequency on duration, but no effects on F0. In contrast, no effects of POS were found on either duration or F0. We conclude that there are no primitive POS effects on duration or F0, but the frequency effect on duration may lead to a weak POS effect given sufficient corpus size.