An electrophysiological investigation of the effects of coreference on word repetition and synonymy

Abstract

In two experiments the effects of word repetition, synonymy, and coreference on event-related brain potentials during text processing were studied. Participants read one (Experiment 1) or two sentence (Experiment 2) texts in which critical nouns were preceded by the definite (the) or indefinite (a) articles. Experiment 1 was run as a control to verify that differences in article processing in the second sentences of Experiment 2 would not contaminate the ERPs to critical noun items. They did not. In Experiment 2, an initial sentence was used to set up a context and contained either a first presentation or synonym of the critical word from the second sentence. N400 (but not Late Positive Component; LPC) priming effects were found for repetitions and synonyms (larger for repetitions) in second sentences. This extends observations of priming in word lists and single sentences to two-sentence texts. There was also a greater left anterior negativity or "LAN" for coreferential critical nouns (those following the article "The") compared to non-coreferential critical nouns (those following the article "A") suggesting that ERPs are sensitive to working memory processes engaged during referential assignment. In response to the articles themselves, there was a greater N400-700 elicited by the article "A" vs. "The." Finally, there was a greater N400-like negativity to the final words of non-coreferential sentences implying that the meanings of these sentences were difficult to integrate with the discourse level representation established by the prior sentence.

Fig. 1

Grand mean ERPs from 15 sites on the head time-locked to the onset of the sentence initial articles in Experiment 1. In this and all subsequent figures the ERP waveforms are plotted at the approximate locations shown in the head schematic located at the top of the figure (note that this is a view looking down at the top of the head with the nose pointed toward the top of the figure). The vertical calibration bar is placed at the time of the onset of the stimulus. Note that 100 ms of activity prior to stimulus onset is displayed (used as a baseline for equating the post-stimulus portion of each waveform).

Fig. 2

Grand mean ERPs for final words from sentences beginning with the articles “The” and “A” (Experiment 1).

Fig. 3

Grand mean ERPs time-locked to articles at the beginning of sentence 2. Note that the ERPs for critical nouns can be seen beginning at about 400 ms after article onset (Experiment 2).

Fig. 4

Grand mean ERPs at the midline sites, time-locked to the article in the second sentence for the two word type conditions (collapsed across coreferential status) in Experiment 2.

Fig. 5

Grand mean ERPs at midline sites for critical nouns in Experiment 2. Note that “antecedents” are words in sentence 1 that are either repeated or are synonyms of the critical words in the second sentence. Filler nouns are the first content words of the second sentence of the filler condition.

Fig. 6

Grand mean ERPs at Cz time-locked to the article in the second sentence comparing the two word type conditions in the coreference condition (on the left) and the non-coreference condition (on the right).

Fig. 7

Grand mean ERPs for final words from sentences beginning with the articles “The” and “A” (Experiment 2).