Predicting this rock: Listeners use redundant phonetic information in online morphosyntactic processing

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 polysyllabic words, like rocket, from monosyllabic words, like rock. This strategy is useful in morphological processing, as additional morphological structure often adds additional syllables. The current study asks (i) whether listeners use these cues to distinguish words that differ only in morphological structure with no change in syllable count (e.g., rock/rocks); and (ii) how surrounding morphosyntactic context affects listeners’ ability to use these cues. Ideal observer models predict that listeners should be attentive to phonetic detail in all contexts regardless of how much new information it offers, while the strategic listener account allows listeners to dynamically adjust their attentiveness to phonetic detail based on its information value in context. In a visual-world eye-tracking study, English-speaking listeners were presented with utterances containing target nouns whose stem durations were manipulated to provide cues to the presence or absence of (a) a plural suffix (rock vs. rocks) or (b) a second, non-morphological syllable (rock vs. rocket). These words were embedded in two contexts: (i) preceded by agreeing determiners, which rendered stem duration cues redundant for predicting the presence or absence of a suffix (this rock/these rocks), and (ii) preceded by non-agreeing determiners (the rock(s)), where stem duration cues carried more information. The results are consistent with ideal observer models: listeners are highly attentive to all acoustic detail, and especially so when it is predictable (and hence redundant), as long as they have the cognitive resources to handle it.