Registered report: investigating a preference for certainty in conversation among autistic adults compared to dyslexic adults and the general population.

Social communication difficulties are a diagnostic feature in autism. These difficulties are sometimes attributed, at least in part, to impaired ability in making inferences about what other people mean. In this registered report, we test a competing hypothesis that the communication profile of adults on the autism spectrum can be more strongly characterised by reduced confidence in making inferences in the face of uncertain information. We will test this hypothesis by comparing the performance of 100 autistic and 100 non-autistic adults on a test of implied meaning, using a test of grammaticality judgements as a control task. We hypothesise that autistic adults will report substantially lower confidence, allowing for differences in accuracy, than non-autistic adults on the test of implied meaning compared to the grammaticality test. In addition, we hypothesise that reduced confidence in drawing inferences will relate to the cognitive trait Intolerance of Uncertainty and self-reported social communication challenges. Finally, we will conduct exploratory analysis to assess the specificity of the communication profile of the autistic adults by comparing their performance to that of dyslexic adults, who might also be expected to experience challenges with language and communication.