Impact of discourse on incremental comprehension processes: Event-related potential studies of word-by-word reading

The studies in this Dissertation used EEG/ERP to examine readers’ incremental, on-line reading comprehension. Study 1 tested the ability of words - as the closing elements of propositions - to trigger outdated mental representations. Participants read text passages in 3 conditions - Consistent, Inconsistent, and Causal. The Inconsistent condition differed from the Consistent condition due to protagonist inconsistencies. Additionally, the Causal condition differed from the Inconsistent condition by the addition of single-sentence causal justifications for the inconsistencies. Electrophysiological results indicated that readers were sensitive to inconsistencies from quite early in word processing, suggesting the functioning of semantically related attentional processes drawn to the meaning features of the input. At later time windows, both words in inconsistent passages and words in causal passages differed from those in consistent passages, with effects varying by scalp location, suggesting related but somewhat functionally distinct memorial processes. Overall, the responses are interpreted as reflecting on-line attentional and memorial mechanisms involved in detecting when a word “doesn’t fit” in a text or discourse, as well those involved when there is more than one available “interpretation” of a text. Study 2 tested the potential effects of contextually-guided referential semantics. Participants read two-sentence texts created to influence a representation that specified one conceptual feature in the first sentence. The second sentence contained a word that was either Consistent or Inconsistent with that feature. The results from Study 2 diverged from predictions in two ways. First, no N400 differences were found between conditions. This was similar to what was found in Study 1 and provides support for a connection between semantic binding and the N400 in connected text. Second, a frontal P600 was found, but in the opposite direction as predicted, with related words eliciting more positive responses than unrelated words. Potentially, this reflects the ability of words in the Feature Consistent texts to act as retrieval cues for related features in the first sentence. In both studies in this Dissertation, effects across levels of linguistic representation were observed, albeit to a lesser extent in Study 2. These findings provide on-line evidence of word-level processing during text comprehension