Comprehending surprising sentences: sensitivity of post-N400 positivities to contextual congruity and semantic relatedness

ABSTRACT

Any proposal for predictive language comprehension must address receipt of less expected information. While a relationship between the N400 and sentence predictability is well established, a clear picture is still emerging of the link between post-N400 positivities (PNPs) and processing of semantically unexpected words, as well as any relation to other not-specifically-linguistic and/or syntactic late positivities. The current study employs event-related brain potentials (ERPs) to congruent and anomalous words to assess the impacts of semantic relatedness and contextual plausibility on processing unpredictable sentences. We observe PNPs with different scalp topographies to plausible unexpected words unrelated to predictable continuations (anterior PNP) and to anomalous words, regardless of, but delayed by, relatedness (posterior PNP). We offer functional explanations that reconcile inconsistencies with reported PNP findings and place added constraints on the anterior PNP’s proposed link to inhibitory processing. We also suggest a testable general cognitive account for the posterior PNP.

KEYWORDS:

• Sentence comprehension
• prediction
• post-N400 positivity (PNP)
• ERP
• language processing

Acknowledgments

The authors wish to thank Janaina Weissheimer for assistance with ERP and behavioural data collection. This work was supported by the NICHD under Grant R01HD22614 to Marta Kutas.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

1 From this point forward, for sake of brevity, we will refer to the more posterior positivity pattern as a pPNP and the anterior one as an aPNP.

2 Only 2 of these 61 contexts had unexpected continuations with non-zero cloze probabilities (.03 and .06 cloze for two CR items). For the remaining 59 contexts, none of the unexpected words ever occurred as norming responses. Cloze probabilities for unexpected continuations across the entire stimulus set were thus presumed to be similarly low.

3 N400 amplitude and plausibility were highly correlated. For N400 condition mean amplitudes over central electrode sites correlated with mean plausibility ratings for the five conditions, Pearson’s r = .9247, p = .0244.

4 A calculation of the correlation between offline plausibility and pPNP mean amplitude between 900 and 1200 ms revealed a strong inverse relationship between the two measures (Pearson’s r = −0.9473, p = .0145 for pPNP condition mean amplitudes over occipital sites correlated with mean condition plausibility ratings for the five conditions).

5 To investigate potential order effects that might be indicative of desensitization to contextual predictability, an exploratory analysis was conducted and is included as supplemental material.

Additional information

Funding

This work was supported by the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) under Grant R01HD22614 to Marta Kutas.