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.

Typical versus delayed speech onset influences verbal reporting of autistic interests.

BACKGROUND: The distinction between autism and Asperger syndrome has been abandoned in the DSM-5. However, this clinical categorization largely overlaps with the presence or absence of a speech onset delay which is associated with clinical, cognitive, and neural differences. It is unknown whether these different speech development pathways and associated cognitive differences are involved in the heterogeneity of the restricted interests that characterize autistic adults. METHOD: This study tested the hypothesis that speech onset delay, or conversely, early mastery of speech, orients the nature and verbal reporting of adult autistic interests. The occurrence of a priori defined descriptors for perceptual and thematic dimensions were determined, as well as the perceived function and benefits, in the response of autistic people to a semi-structured interview on their intense interests. The number of words, grammatical categories, and proportion of perceptual/thematic descriptors were computed and compared between groups by variance analyses. The participants comprised 40 autistic adults grouped according to the presence (N = 20) or absence (N = 20) of speech onset delay, as well as 20 non-autistic adults, also with intense interests, matched for non-verbal intelligence using Raven's Progressive Matrices. RESULTS: The overall nature, function, and benefit of intense interests were similar across autistic subgroups, and between autistic and non-autistic groups. However, autistic participants with a history of speech onset delay used more perceptual than thematic descriptors when talking about their interests, whereas the opposite was true for autistic individuals without speech onset delay. This finding remained significant after controlling for linguistic differences observed between the two groups. CONCLUSIONS: Verbal reporting, but not the nature or positive function, of intense interests differed between adult autistic individuals depending on their speech acquisition history: oral reporting of intense interests was characterized by perceptual dominance for autistic individuals with delayed speech onset and thematic dominance for those without. This may contribute to the heterogeneous presentation observed among autistic adults of normal intelligence.