For most words of English in most spoken contexts, the location of the main stress syllable is clear. However, for words in which (a) the main lexical stress is not obvious from the phoneme string alone (e.g., main-stress-ambiguous words like ‘‘digest’’ and ‘‘increase,’’ and certain proper names), and (b) the possible positions for the main stress consist of adjacent full-vowel syllables, an ambiguity in the location of the prominence and, consequently, in the identity of the lexical item (for main-stress-ambiguous words) is observed when these words occur in contexts with certain F0 configurations extending across the adjacent full-vowel syllables (e.g., a rise followed by a peak, or a peak followed by a fall; F0 peaks frequently dissociate from lexically stressed syllables [Ladd (1996)]). In these cases, the syllable affiliation of the main lexical stress is unclear; either the peak or movement (rise or fall) in the F0 contour can be heard as the prominence. This suggests that listeners interpret F0/syllable alignment in light of their language knowledge and a set of perceptual proclivities [Handel (1989)]. When the language fails to specify enough information or two perceptual proclivities are in conflict, perceptual ambiguity can result.