Distinguishing speed from accuracy in scalar implicatures

Scalar implicatures are inferences that arise when a weak expression is used instead of a stronger alternative. For example, when a speaker says, ‘‘Some of the children are in the classroom,’’ she often implies that not all of them are. Recent processing studies of scalar implicatures have argued that generating an implicature carries a cost. In this study we investigated this cost using a sentence verification task similar to that of Bott and Noveck (2004) combined with a response deadline procedure to estimate speed and accuracy independently. Experiment 1 compared implicit upper-bound interpretations (some [but not all]) with lower-bound interpretations (some [and possibly all]). Experiment 2 compared an implicit upper-bound meaning of some with the explicit upper-bound meaning of only some. Experiment 3 compared an implicit lower-bound meaning of some with the explicit lower-bound meaning of at least some. Sentences with implicatures required additional processing time that could not be attributed to retrieval probabilities or factors relating to semantic complexity. Our results provide evidence against several different types of processing models, including verification and nonverification default implicature models and cost-free contextual models. More generally, our data are the first to provide evidence of the costs associated with deriving implicatures per se. 2011 Elsevier Inc. All rights reserved.