Dissociation Between Linguistic and Nonlinguistic Statistical Learning in Children with Autism

Abstract

Background: Children with autism spectrum disorder (ASD) exhibit highly variable language abilities. There is a great interest in whether statistical learning (SL), a fundamental mechanism for language development, is impaired in ASD. Nevertheless, mixed findings have been reported. Furthermore, recent studies in healthy populations suggest individuals vary in their SL ability across auditory and visual modalities as well as linguistic and nonlinguistic domains. Whether children with ASD show impaired SL in specific modalities or domains still remains unknown.Methods: Thirty-one children with ASD (6 – 12 years) and 31 age and gender-matched typically developing (TD) children were assessed with an auditory linguistic (syllable), auditory nonlinguistic (tone), visual linguistic (letter), and visual nonlinguistic (image) SL tasks where children implicitly learned the embedded patterns of stimulus triplets. Learning was measured by reaction-time acceleration during familiarization, triplet-recognition accuracy after familiarization, and a composite score combining online and offline learning.Results: Children with ASD showed particular weaknesses in the linguistic SL tasks (syllable and letter) but comparable performance to the TD children in the nonlinguistic SL tasks (tone and image). Children with ASD showed a lack of association across SL tasks, suggesting distinct underlying learning processes for SL across domains and modalities. The specific weaknesses in linguistic SL appear to be more evident in older children with ASD compared to younger children with ASD.Conclusions: We found children with ASD are not in general impaired in SL. Instead, their difficulties lie specifically in the linguistic domains. We also provided preliminary evidence hinting a reciprocal relationship between linguistic SL and language development, as the weaknesses in linguistic SL exacerbate over development in our cross-sectional sample. Future longitudinal research will elucidate whether impaired linguistic SL is an outcome or a cause of impaired language skills in a substantial subgroup of children with ASD.