Ad-hoc and scalar implicatures in children with autism spectrum disorder

Background: Previous studies found that people with Autism Spectrum Disorder (ASD) perform well on pragmatic inference tests that require the use of the linguistic scale . The present study extends previous research by testing two types of implicature: scalar implicatures, based on lexical scales, and ad-hoc implicatures, based on contextual scales. Methods: We tested 26 children with ASD aged 4-10 years (mean age 7.1) and 26 typically developing (TD) children - matched on chronological age and with a similar performance in non-verbal IQ and vocabulary - by means of a picture selection task for scalar and ad-hoc implicatures. We also investigated the effect of children's scores in standardized tests measuring non-verbal intelligence, lexical, and morphosyntactic abilities and Theory-of-Mind skills on their performance in the implicature tasks. Results: Although more than half of the children with ASD performed above chance on both kinds of implicatures, their performance as a group was significantly lower than the performance of their TD peers. General cognitive abilities were found to affect the performance of children with ASD on both kinds of implicatures, and Theory-of-Mind reasoning skills were found to be linked to their performance on scalar, but not ad-hoc implicatures. Conclusions: We show that children with ASD have difficulty with both kinds of implicatures. These findings may have implications for explanatory theories of pragmatics as well as for clinical work with children with ASD.