Abstract: Using a violation paradigm, Hagoort et al. observed that world knowledge and word meaning are integrated simultaneously at the end of a sentence. The present study was intended to track the time course of integration of world knowledge in sentence comprehension when world knowledge is embedded in a sentence rather than at the sentence end.
The materials used were four-word sentences. The second word in the sentences was the target word that could contain information leading to semantic or world knowledge violations. Event-related brain potentials (ERPs) induced by the last three words in each sentence were recorded and compared across three conditions, the word meaning violation condition, the world knowledge violation condition, and the non-violation normal congruence condition.
Compared with non-violation congruous sentences, presentation of the target message in world knowledge violation sentences immediately evoked a typical N400. As the sentence unfolded, the subsequent words in the sentence did not produce similar N400 effect except at the sentence end when a negative N400-like component was observed. It is noted that while the N400 evoked by the violation target words showed no obvious hemispheric asymmetry, the one evoked by the ending words showed right hemisphere dominance. Compared with word meaning violation sentences, there were no other ERP waveform differences except that the N400 amplitude was much smaller for world knowledge violation than word meaning violation.
The results indicate that world knowledge, similar to word meaning, could be integrated instantly as the sentence unfolds during sentence comprehension and outcome of this integration process does not affect processing of subsequent information. Integrated world knowledge manifested earlier could be reactivated however when the reader reaches the sentence end and makes judgment about the facticity of the whole sentence.

Key words: N400, world knowledge, sentence comprehension