ERP studies of visual and auditory processing of negated sentences

In two event-related potential studies, we investigated the processing of sentences with prefixal negation (unauthorized), sentential negation (not authorized) and no negation (authorized). We asked whether prefixal and sentential negation resulted in delayed processing. In Experiment 1, sentences such as “The White House announced that the new Obama biography was authorized/unauthorized/not authorized therefore the details in the book were correct/wrong in actual fact” were presented visually word by word and were followed by a forced binary-choice task (“Did the sentence make sense?”). The underlined words indicate the manipulations and the bold words indicate the critical words. In Experiment 2, the same sentences were presented auditorily. In both experiments, ERPs to the critical words were analyzed. The results suggest that in both experiments, the False version of non-negated sentences (authorized combined with wrong) elicited a larger N400 and P600 than the True version (authorized combined with correct). Sentences with prefixal and sentential negation in the visual experiment were related to slower processing suggesting a delay in integrating negation. However, in the auditory study, False sentences elicited increases in the P600 suggesting that both negation forms were successfully processed. The difference in processing the negated forms between the two modalities could be explained by the fact that the auditory paradigm allowed for a faster presentation and participants could thus keep the negated forms in working memory, while the visual study was, due to a slower presentation, more demanding on the working memory requiring an activation of the negated meanings as the critical words appeared.