Scalar Implicature in Absence of Epistemic Reasoning? The Case of Autism Spectrum Disorder

ABSTRACT

We investigated “scalar implicature” in adolescents and children with autism spectrum disorder (ASD) to test whether theory of mind deficits associated with autism affect pragmatic inferences in language. We tested scalar implicature computation in adolescents with ASD (12–18 years) and asked whether they reason about mental states when computing inferences. Like previous studies, we found the adolescents with ASD computed implicatures to the same degree as neurotypical adults. However, we also found that this ability may not rely on epistemic reasoning. In a test of epistemic reasoning (which probed so-called “ignorance implicature”) we found that adolescents with ASD were able to make epistemic inferences required by Gricean models of scalar implicature when they were explicitly required by the task to do so. However, in a second task, which asked whether subjects spontaneously reason about mental states in the service of scalar implicature when not explicitly asked to, we found that adolescents with ASD did not engage in epistemic reasoning, leading them to compute scalar implicatures in contexts in which they were not justified. Based on these data, we argue that epistemic reasoning may not be a core, constitutive component of scalar implicature.

Acknowledgments

Many thanks to Danny Fox, Karen Dobkins, Melissa McIntire, Shereen Cohen, Katherine Stavropoulos, Katie Kimura, Katie Wagner, Laura Taouk, Troy Campbell, Daisy Hong, Valerie’s List, members of the UCSD Developmental Brown bag, the Language and Development Lab, and AndyLab, and to all the families that participated in this study.

Funding

Funding for this project was provided through a grant from the James S. McDonnell foundation.

Notes

¹ Technically, not just “stronger” alternatives, but also those that are not weaker than the original sentence.

² There is an important distinction between an ignorance implicature, the inference that the speaker doesn’t know whether a given proposition is true or false, vs. a weak inference, the inference that the speaker doesn’t believe a proposition to be true when their knowledge/ignorance status is unknown (see the discussion in Geurts, 2010). However, this distinction is not critical in relation to the experimental results presented in this paper. Therefore, we will call both type of inference ignorance implicatures for the sake of the following discussion.

³ As we report below, it was not necessary to collect data for age-, language-, or IQ-matched neurotypical adolescents, since the adolescents with ASD did not differ even from our neurotypical adults on any measures in the Ignorance Implicature or Scalar Implicature tasks, and only differed on 2 out of 4 critical trials in the Speaker Knowledge task (and did not differ on control trials in this task). Specifically, they differ on trials that required suspending scalar implicatures based on epistemic reasoning. In summary, a comparison to neurotypical adults makes a very strong case that adolescents with ASD are very much unimpaired in almost all cases.

⁴ Subjects were only allowed to proceed once they responded to this question correctly. If subjects answered incorrectly, the experimenter demonstrated again which boxes Farmer Brown had looked inside, and asked subjects the question again.

Additional information

Funding

Funding for this project was provided through a grant from the James S. McDonnell foundation.