Slowdowns in scalar implicature processing: Isolating the intention-reading costs in the Bott & Noveck task

An underinformative sentence, such as Some cats are mammals, is trivially true with a semantic (some and perhaps all) reading of the quantifier and false with a pragmatic (some but not all) one, with the latter reliably resulting in longer response times than the former in a truth evaluation task (Bott & Noveck, 2004). Most analyses attribute these prolonged reaction times, or costs, to the steps associated with the derivation of the scalar implicature. In the present work we investigate, across three experiments, whether such slowdowns can be attributed (at least partly) to the participant's need to adjust to the speaker's informative intention. In Experiment 1, we designed a web-based version of Bott & Noveck's (2004) laboratory task that would most reliably provide its classic results. In Experiment 2 we found that over the course of an experimental session, participants' pragmatic responses to underinformative sentences are initially reliably long and ultimately comparable to response times of logical interpretations to the same sentences. Such results cannot readily be explained by assuming that implicature derivation is a consistent source of processing effort. In Experiment 3, we further tested our account by examining how response times change as a function of the number of people said to produce the critical utterances. When participants are introduced (via a photo and description) to a single 'speaker', the results are similar to those found in Experiment 2. However, when they are introduced to two 'speakers', with the second 'speaker' appearing midway (after five encounters with underinformative items), we found a significant uptick in pragmatic response latencies to the underinformative item right after participants' meet their second speaker (i.e. at their sixth encounter with an underinformative item). Overall, we interpret these results as suggesting that at least part of the cost typically attributed to the derivation of a scalar implicature is actually a consequence of how participants think about the informative intentions of the person producing the underinformative sentences.