Acoustic-phonetic correlates of stress shift

Abstract

Many speakers of American English exhibit “stress shift,” in which the lexical prominence of a polysyllabic word seems to shift to an earlier syllable, as when “thirTEEN” becomes “THIRteen” in “THIRteen MEN,” or “MissisSIPpi” becomes “MISsissippi MUD.” Fundamental frequency and duration measurements suggest that this is a phrase-level phenomenon that arises from the confluence of two separate events: (a) The pitch accent occurs not on the target Word, but on a different word of the phrase (here “MEN” and “MUD”); and (b) another phrasally based pitch rise occurs on the earlier syllable of the target word (here “THIR-” and “MIS-”). Three lines of evidence support this account: (1) The first rise can occur even earlier, i.e., on a preceding word, suggesting a domain larger than the individual lexical item; (2) under certain conditions of phrasal prosody, for the same word string, the pitch accent returns to the location of the lexically stressed syllable of the target word, showing that the “shift” does not result simply from the lexical stress patterns of adjacent words; and (3) the two types of pitch excursion can have different characteristics, indicating that the early rise and the pitch accent are separate phenomena. These observations are consistent with the hypothesis that pitch marking occurs on lexically stressed syllables when phrasal prosody requires it, but not otherwise.