Lexical Inhibition due to Failed Prediction: Behavioral Evidence an ERP Correlates

During sentence processing, comprehenders form expectations regarding upcoming material, and may even predict a specific word. Previous event-related potential (ERP) studies have shown that disconfirmed predictions elicit a post-N400-positivity (PNP) with two distinct distributions. A frontal-PNP (f-PNP) is elicited when an unexpected but congruent word appears instead of a highly predictable word. whereas an anomalous word elicits a posterior-PNP. The current study tested the hypothesis that during the processing of a sentence, the predicted word is inhibited to enable the integration of unexpected but congruent material, and that this inhibitory process is reflected in the f-PNP component. In contrast, anomalous continuations, which are not compatible with the preceding context, do not induce inhibition. Experiment 1 used cross-modal lexical priming to test inhibition patterns of predicted words, demonstrating inhibition when integration of a congruent-unexpected word was needed, but not when an anomaly was encountered. Experiment 2 showed that the inhibition observed in Experiment 1 is specific to the predicted word and does not stem from competition between two congruent continuations. In Experiment 3 we recorded ERPs using the same materials, and found that the f-PNP component is elicited under the same conditions giving rise to behavioral inhibition, and that the two are correlated, thus providing preliminary support for the hypothesis that this component reflects an inhibitory process.