Abstract
BACKGROUND: Unexpected bilingualism (UB) in autism, in which children speak languages not spoken in their social environment, has been sporadically reported. UB implies that autistic children can acquire languages in a non-socially interactive way. The early minimally verbal period in autism could be critical for non-interactive language acquisition, given the predominance of non-social interests at that time. However, evidence of language acquisition outside social interaction during this period remains limited and restricted to small case studies. METHODS: Caregivers of 119 autistic, 102 non-autistic clinical, and 75 typically developing (TD) children aged 2-6 years completed a structured questionnaire about their children's language-related interests and use. They were also asked to estimate the relative proportion of each language their children were exposed to in their social environment. UB was operationalized as the use of at least one language not spoken in the child's social environment to name letters and/or numbers. RESULTS: Of the autistic group, 53% were considered minimally verbal. A total of 38.7% of autistic children displayed UB, with autistic children being 4.38 times more likely to show UB than TD children (p < .001). In contrast, the non-autistic clinical children did not differ significantly from TD children. The presence of UB was not associated with the children's expressive language level. Autistic children were 8.28 times more likely than TD children to use a non-dominant language (here English) (p < .001), after controlling for their proportion of social exposure to that language. Non-interactive media were the only sources caregivers reported to explain the presence of UB in autistic children. CONCLUSIONS: Autistic children, even those who are minimally verbal, are less dependent on their social environment for specific aspects of language development. Non-interactive pathways of language acquisition may have a prominent role in early language development in autism.