When heuristics clash with parsing routines: ERP evidence for conflict monitoring in sentence perception

摘要

Monitoring refers to a process of quality control, designed to optimize behavioral outcome. Monitoring for action errors manifests itself in a Error-related Negativity in ERP studies and in an increase in activity of the anterior cingulate in fMRI studies. Here we report evidence for a monitoring process in perception, in particular language perception, manifesting itself in a late positivity in the ERP. This late positivity, the P600, appears to be triggered by a conflict between two interpretations, one delivered by the standard syntactic algorithm and one by a plausibility heuristic which combines individual word meanings in the most plausible way To resolve this conflict, we propose that the brain reanalyzes the memory trace of the perceptual input, to check for the possibility of a processing error. So when, as in Experiment 1, the reader is presented with semantically anomalous sentences like the fox that shot the poacher…, full syntactic analysis indicates a semantic anomaly, while the word-base heuristic leads to a plausible interpretation, that of a poacher shooting a fox. That readers actually pursue such a word-based analysis is indicated by the fact that the usual ERP index of semantic anomaly, the so-called N400 effect, was absent in this case. A P600 effect appeared instead. In Experiment 2, we found that even when the word-based heuristic indicated that only part of the sentence was plausible (e.g., ..that the elephants pruned the trees), a P600 effect was observed while the N400 effect of semantic anomaly was absent. It thus seems that the plausibility of part of the sentence (e.g., that of pruning trees), was sufficient to create a conflict with the implausible meaning of the sentence as a whole, giving rise to a monitoring response;