Explicit and implicit negation , negative polarity , and levels of semantic representation

Most previous studies on negation have generally only focused on sentential negation (not), reporting cost and delay associated with computing its meaning. In an ERP study (Experiment 1), we make use of the negation-sensitivity of negative polarity items (NPIs) and examine the time course of processing different kinds of negation. Four kinds of NPI-licensing environments were examined: the negative determiner no, the negative determiner few, the focus marker only, and emotive predicates (e.g., surprised). While the first three contribute a negative meaning via assertion (explicit negation), the last gives rise to a negative inference via non-asserted content (implicit negation). Under all these environments, an NPI elicited a smaller N400 as well as a smaller late anterior negativity, compared to an unlicensed NPI, suggesting that negation, regardless of its source, is rapidly computed online, contrary to previous findings. However, we also observed that explicit negative meaning (e.g., as contributed by the first three licensors) and implicit negative meaning (contributed by emotive predicates) were integrated into the grammatical representation in different ways, leading to a difference in the P600, and calling for a separation of distinct levels of semantic integration during sentence processing. The qualitative differences between these conditions were also replicated in a self-paced reading study (Experiment 2).