Going the Extra Mile: Effects of Discourse Context on Two Late Positivities During Language Comprehension

Area of Science:

• Cognitive Neuroscience
• Psycholinguistics
• Computational Linguistics

Background:

• Language comprehension relies on predicting upcoming words based on prior context.
• The N400 event-related potential (ERP) reflects semantic predictability.
• Late positive ERPs, including the late posterior positivity/P600 and late frontal positivity, are less understood in response to prediction violations.

Purpose of the Study:

• To investigate how context length and the source of lexical constraint influence neural responses to prediction violations.
• To differentiate the neural correlates of semantic anomalies versus lexical prediction errors.
• To test predictions from a hierarchical generative model of language comprehension.

Main Methods:

• Three experiments manipulating context length (minimal vs. extended discourse) and constraint type (semantic vs. lexical).
• Electrophysiological recordings (ERPs) measuring brain responses to words in different contexts.
• Analysis of N400, late posterior positivity/P600, and late frontal positivity components.

Main Results:

• Minimal contexts elicited larger N400s for both semantic and lexical violations but no late positive effects.
• Late posterior positivity/P600 emerged for semantic anomalies in longer discourse contexts.
• Late frontal positivity appeared for lexical prediction violations in rich, globally constraining contexts.

Conclusions:

• Contextual richness and comprehension goals modulate neural responses to prediction errors.
• Late positive ERPs reflect distinct reanalysis processes for semantic versus lexical violations.
• Findings support a hierarchical generative framework where context influences prediction and reanalysis.