An event-related brain potential (ERP) reflecting the acoustic-phonetic process in the phonological stage of word processing was recorded to the terminal words of spoken sentences. The peak latency of this negative-going response occurred between 270 and 300 msec after the onset of the terminal word. The independence of this response (the phonological mismatch negativity, PMN) from the ERP component known to be sensitive to semantic violations (N400) was demonstrated by manipulating sentence endings so that phonemic and semantic violations occurred together or separately. Four conditions used sentences that ended with (1) the highest Cloze probability word (e.g., “The piano was out of tune.”), (2) a word having the same initial phoneme of the highest Cloze probability word but that was, in fact, semantically anomalous (e.g., “The gambler had a streak of bad luggage.”), (3) a word having an initial phoneme different from that of the highest Cloze probability word but that was, in fact, semantically appropriate (e.g., “Don caught the ball with his glove.”), or (4) a word that was semantically anomalous and, therefore, had an initial phoneme that was totally unexpected given the sentence's context (e.g., “The dog chased our cat up the queen”). Neither the PMN nor the N400 was found in the first condition. Only an N400 was observed in the second condition while only a PMN was seen in the third. Both responses were elicited in the last condition. Finally, a delayed N400 occurred to semantic violations in the second condition where the initial phoneme was identical to that of the highest Cloze probability ending. Results are discussed with regard to the Cohort model of word recognition.

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