Noun/verb distinction in English stress homographs: an ERP study

Sensitivity to speech rhythm, especially the pattern of stressed and unstressed syllables, is an important aspect of language acquisition and comprehension from infancy through adulthood. In English, a strong correlation exists between speech rhythm and grammatical class. This property is well illustrated by a particular group of noun/verb homographs that are spelled the same but are pronounced with a lexical stress on the first syllable when used as a noun or on the second syllable when used as a verb. The purpose of this study was to further examine the neural markers of speech rhythm and its role in word recognition. To this end, event-related brain potentials were recorded while participants listened to spoken sentences containing a stress homograph either in a noun or a verb position. The rhythmic structure of the stress homographs was manipulated so that they were pronounced with a stress pattern that either matched or mismatched their grammatical class. Results of cluster-based permutation tests on the event-related brain potentials revealed larger negativities over the centrofrontal scalp regions when the stress homographs were mispronounced, in line with previous studies on lexical ambiguity resolution. In addition, differences between rhythmically unexpected nouns and verbs could be seen as early as 200ms, suggesting that listeners are sensitive to statistical properties of their language rhythm. Together, these results support the hypothesis that information about speech rhythm is rapidly integrated during speech perception and contributes to lexical retrieval.