Just to be safe: Listeners use redundant phonetic information to distinguish unsuffixed from suffixed nouns

Pronunciation variation is systematic, and provides listeners with cues to what the speaker is about to say. Shortened stems, for example, can indicate an upcoming suffix, while lengthened ones can indicate a word boundary follows. Previous work has shown that listeners draw on these cues to distinguish multisyllabic from monosyllabic target words. In this project, we ask whether (i) listeners use these cues to distinguish words that differ only in morphological structure with no change in syllable count; (ii) whether the redundancy of these cues in the immediate sentence affects listener attentiveness; and (iii) whether linguistic experience can change how listeners learn or use these cues. In two visual-world eye-tracking studies, in English and Spanish, we presented listeners with utterances containing target nouns whose stem durations were manipulated to provide cues to the presence or absence of a plural suffix. The redundancy of these cues was manipulated across different sentence contexts: Sentences in which agreeing determiners indicated noun number rendered the stem duration cues redundant, while sentences with no determiners rendered the cues more informative. In both experiments, listeners attended to acoustic cues signalling an upcoming suffix even when the sentence context rendered such cues redundant. Further, in Experiment 2 high-proficiency Spanish-English bilinguals were more sensitive to such cues than low-proficiency bilinguals, suggesting a phonetic bilingual advantage in speech perception. These results are consistent with ideal observer models in which listeners are attentive to all acoustic detail, regardless of whether it is informative or redundant.