Nieuwland, M. & Martin, A.
Basque Center on Cognition, Brain and Language
Counterfactual statements describe imaginary consequences of hypothetical events. Counterfactual comprehension provides an interesting test-case for studying the interaction between real-world knowledge and discourse context because counterfactuals may require keeping in mind what is true and what is false (Byrne, 2002). Recent event-related potential (ERP) and eye-tracking results suggest that real-world knowledge briefly interferes with counterfactual comprehension (Ferguson & Sanford, 2008; Ferguson, Sanford & Leuthold, 2008), consistent with two-stage accounts of discourse comprehension. Yet, the validity of these results stands or falls with the provision of a sufficiently constraining discourse. In an ERP experiment, we tested whether real-world interference upholds in the face of a strong counterfactual context. Participants read Spanish counterfactually true/false statements (approximate translation: “If N.A.S.A. had not developed its Apollo Project, the first country to land on the moon would be Russia/America”) and real-world true/false statements (“Because N.A.S.A. developed its Apollo Project, the first country to land on the moon has been America/Russia\") that were matched for critical word expectancy and for rated truth-value. Our hypothesis involved N400 amplitude, which indexes early semantic processing costs and is sensitive to subtle variations in discourse-semantic fit (Kutas, Van Petten & Kluender, 2006). If real-world knowledge interferes, if only briefly, with counterfactual comprehension despite this strong context, critical words in counterfactually true statements should evoke larger N400s compared to counterfactually false statements and real-world true statements. In contrast, if incoming words are mapped onto the most relevant interpretive context without delay and without initial regard to pre-stored real-world knowledge, false statements elicit an N400 effect compared to true statements, for counterfactual and real-world statements alike. Our ERP results are consistent with this latter prediction, and argue against automatic interference from pre-stored real-world knowledge during counterfactual comprehension. Instead, incoming words in counterfactual statements are evaluated foremost in terms of their contextual relevance.