Preservation of categorical perception for speech in autism with and without speech onset delay

Recent accounts of autistic perception, including Bayesian accounts, hypothesize a reduced influence of prior knowledge on perception across different domains in the autism spectrum (AS). The purpose of this study was to investigate the influence of prior linguistic knowledge, in the form of phonemic categorical knowledge, on speech perception in adults with AS condition. As phonemic categorical knowledge is shaped by language experience and abilities, we furthermore distinguished AS participants with (AS-SOD) or without a history of speech onset delay (AS-noSOD); the control group comprises typical individuals matched for age, nonverbal intelligence, and reading abilities. We also controlled for the influence of auditory-verbal short-term retention capacities by administering word list and nonword list repetition tasks. We did not observe any reduced influence of prior phonemic knowledge on the perception of speech stimuli nor did we observed any increased perceptual abilities for atypical variants of speech stimuli or nonspeech auditory stimuli, either between the two autistic groups or relative to the control group. Short-term memory abilities appeared to be superior in the AS-noSOD group relative to the AS-SOD and control groups, but this strength could be accounted for by their higher vocabulary knowledge. The preservation of categorical perception in verbal autistic adults observed in this study challenges models claiming a reduced influence of prior knowledge on perception across domains in the AS. Autism Res 2019. © 2019 International Society for Autism Research, Wiley Periodicals, Inc. LAY SUMMARY: A reduced influence of prior knowledge has been considered to characterize perceptual abilities in people with autism. In this article, we examine this claim by assessing nonlinguistic and linguistic auditory perception abilities in adults with autism, and by further distinguishing between autism with or without a history of delayed language development. We did not observe any reduced influence of prior language knowledge on the perception of speech stimuli nor did we observe any increased perceptual abilities for atypical variants of speech stimuli or nonspeech auditory stimuli, and this relative to a control group matched on age, nonverbal intellectual efficiency, and reading abilities. Our results challenge models claiming a reduced influence of prior knowledge on perception across domains in the AS.