Background: Children with intellectual disabilities (IDs) have a severe delay in syntactic development compared with other language abilities. This study investigated conditions of syntactic development in native Japanese-speaking children with ID.
Methods: Children with ID [N = 51; 18 autism spectrum disorders (ASD), 18 Down syndrome (DS) and 15 ID without ASD and DS] were compared with typically developing children (N = 78) with the same mental age (MA). The development of syntax in spoken language was examined by receptive and production tasks.
Results: The development of syntax in children with ID was significantly delayed than in typically developing children with the same MA. However, when reaching the MA of 7-9, syntax abilities started to develop remarkably. Moreover, children with ASD had significant difficulties in acquiring passive voice, whereas children with DS showed a significant delay in syntactic development.
Conclusions: The development of syntax in children with ID might be affected by MA and the type of disability. Moreover, it is necessary to exceed an MA of 7-9 years for children with ID to develop syntax abilities.
Keywords: intellectual disabilities; language development; language disorders; syntactic development.
© 2019 MENCAP and International Association of the Scientific Study of Intellectual and Developmental Disabilities and John Wiley & Sons Ltd.