An Experimental Comparison between Presuppositions and Indirect Scalar Implicatures

We compare two aspects of meaning, namely the presupposition of stop in the scope of negation (John didn’t stop going to the movies on Wednesday., → John used to go to the movies before Wednesday.) and scalar implicatures associated with strong scalar items under negation (John didn’t always go to the movie last week. → John sometimes went to the movies last week.) (‘Indirect Scalar Implicatures’ (ISIs) Chierchia, 2004). Our results replicate the finding by Chemla and Bott (2013) that global presupposition interpretations are faster with a different methodology that avoids a potential confound of response bias. More surprisingly, ISIs are found to pattern with presuppositions in that responses reflecting an interpretation without an inference (corresponding to a ‘literal’ interpretation) are slower than ones based on the relevant inference, contrary to what has been found for direct scalar implicatures. These results are puzzling from the traditional perspective that ISIs are generated in the same way as direct implicatures. We explore two possible interpretations: first, strong scalar terms could receive a presuppositional analysis as well and presuppose that their domain is non-empty. Alternatively, we could group stop and ISIs together from another angle and see them as obligatory scalar implicatures, in contrast to the non-obligatory direct ones.