'Negation-blind' N400 effect disappears when lexical priming is controlled

Abstract

Previous ERP studies showed that false affirmative sentences elicited a larger N400 than their true versions, but they found the reverse pattern when the sentences were of negative form as if N400 was blind to negation. This negation-blind N400 pattern arguably constituted evidence for two-step accounts of negation processing: When processing negative sentences, a comprehender first computes an internal proposition and then considers the negation. However, the prior studies were confounded by a lexical priming relation between subject and object. Therefore, it was an open question whether or not the observed ERP pattern really reflected the two-step process. To tackle this question, we conducted an ERP experiment, using size-comparison statements where subjects and objects are semantically unrelated. This design allowed us to remove the priming confound. We predicted that if the previous negation-blind N400 pattern is unrelated to lexical priming, it would be replicated; if not, it would disappear. The result was consistent with the second prediction. This suggests that the previously observed negation-blind N400 pattern does not necessarily constitute evidence for two-step accounts of negation processing.