| dc.description | The degree to which phonological codes influence the word identification process has been debated. Event-related brain potentials (ERPs) have been used to investigate the processes involved in language. The N400 is a negative-going neural component that occurs approximately 400 ms post-stimulus. This component has been shown to be sensitive to semantic priming and occurs reliably to semantically incongruous, and therefore unexpected, terminal words of sentences. A series of sentences with high contextual constraint were visually presented in each of the four experiments. ERPs were recorded to the sentence-ending stimuli which completed the sentences in either a congruous or incongruous manner. Each of the 4 experiments investigated whether phonological codes influenced sentence reading when factors shown to diminish this effect in behavioural tasks were introduced. Phonologically ambiguous words (i.e., homophone foils) or non-words (i.e., pseudofoils) were used in each experiment to measure the effect of phonological recoding. The results of these studies showed that the N400 component responded differentially to semantically unexpected sentence-ending stimuli. This differential response depended upon whether or not they were phonologically identical to the high cloze probability words for the sentences. The N400 responses that were elicited by phonologically unexpected stimuli were significantly larger than those elicited by phonologically expected lexical and non-lexical stimuli. One exception to this pattern was observed in Experiment I when subjects performed a semantic judgement task and incongruous terminal words produced N400 responses regardless of whether they were phonologically expected. The evidence for phonological recoding was not attributable to orthographic similarity. However, some evidence was obtained which suggested that an earlier occurring negative-going component, the N270, was sensitive to deviations in orthographic expectancy for the sentence-ending stimuli. Overall, these findings demonstrate that ERPs are useful for investigating the subtle processes involved in language. Further, these results support theoretical models that propose an important role for phonology during word recognition. | en_US |
