Listeners maintain phonological uncertainty over time and across words: The case of vowel nasality in English

Abstract

While the fact that phonetic information is evaluated in a non-discrete, probabilistic fashion is well established, there is less consensus regarding how long such encoding is maintained. Here, we examined whether people maintain in memory the amount of vowel nasality present in a word when processing a subsequent word that holds a semantic dependency with the first one. Vowel nasality in English is an acoustic correlate of the oral vs. nasal status of an adjacent consonant, and sometimes it is the only distinguishing phonetic feature (e.g., bet vs. bent). In Experiment 1, we show that people can perceive differences in nasality between two vowels above and beyond differences in the categorization of those vowels. In Experiment 2, we tracked listeners’ eye-movements as they heard a sentence that mentioned one of four displayed images (e.g., ‘money’) following a prime word (e.g., ‘bet’) that held a semantic relationship with the target word. Recognition of the target was found to be modulated by the degree of nasality in the first word’s vowel: Slightly greater uncertainty regarding the oral status of the post-vocalic consonant in the first word translated into a weaker semantic cue for the identification of the second word. Thus, listeners appear to maintain in memory the degree of vowel nasality they perceived on the first word and bring this information to bear onto the interpretation of a subsequent, semantically-dependent word. Probabilistic cue integration across words that hold semantic coherence, we argue, contributes to achieving robust language comprehension despite the inherent ambiguity of the speech signal.