Purpose: The present study explored the extent to which early prelinguistic communication skills predict expressive language in toddlers with autistic siblings (Sibs-autism), who are known to be at high likelihood for autism and language disorder, and a comparison group of toddlers with non-autistic older siblings (Sibs-NA). Method: Participants…

Fragile X syndrome (FXS), the leading heritable cause of intellectual disability, has a co-occurrence rate of autism spectrum disorder (ASD) estimated at ~60%. The onset and rates of motor development in FXS are slower relative to neurotypical development, and even more so in the context of co-occurring FXS + ASD. Extant evidence suggests these…