The neural underpinnings of semantic ambiguity and anaphora.

We used event-related brain potentials (ERPs) in order to investigate how definite NP anaphors are integrated into semantically ambiguous contexts. Although sentences such as Every kid climbed a tree lack any syntactic or lexical ambiguity, these structures exhibit two possible meanings, where either many trees or only one tree was climbed. This semantic ambiguity is the result of quantifier scope ambiguity. Previous behavioural studies have shown that a plural definite NP continuation is preferred (as reflected in a continuation sentence, e.g., The trees were in the park) over singular NPs (e.g., The tree was in the park). This study aimed to identify the neurophysiological pattern associated with the integration of the continuation sentences, as well as the time course of this process. We examined ERPs elicited by the noun and verb in continuation sentences following ambiguous and unambiguous context sentences. A sustained negative shift was most evident at the Verb position in sentences exhibiting scope ambiguity. Furthermore, this waveform did not differentiate itself until 900 ms after the presentation of the Noun, suggesting that the parser waits to assign meaning in contexts exhibiting quantifier scope ambiguity, such that such contexts are left as underspecified representations. Copyright 2009 Elsevier B.V. All rights reserved.