Polarity and the speed of scalar implicature processing

Scalar implicatures (SIs) such as the inference from “some” to “but not all” are known to vary in processing cost. According to the Polarity Hypothesis (van Tiel et al., 2019; van Tiel and Pankratz, 2021), this cost depends on the polarity of the scalar term: SIs from positively polar expressions (e.g., “some”) are expected to be slower to compute than literal interpretations, while the reverse should hold for SIs from negatively polar expressions (e.g., the inference from “not all” to “but some”). We tested this prediction in a sentence--picture verification experiment with 538 English-speaking participants. Each participant judged whether sentences containing weak or strong scalar terms matched a corresponding picture, allowing us to measure response times as an index of processing effort. While our omnibus analysis found no reliable response–polarity–condition interaction, scale-specific analyses revealed mixed results: One pair of scales showed the predicted interaction, one showed a reversed effect, and two showed no effect. A meta-analysis combining our data with prior studies yielded moderate support for the Polarity Hypothesis. We conclude that polarity may influence the speed of scalar implicature processing, but that this effect is not robust across all scalar domains.