Lay abstract

About one-third of children with autism spectrum disorder never develop the language that they need in different day-to-day situations. Identifying potential factors that can predict later language development is crucial to understanding why some children with autism spectrum disorder successfully develop language while others do not. This study sought to investigate one of the understudied predictors of language development, social motivation, and to test theories for why this association may occur. Testing the theories requires that we measure children's ability to deliberately and directly communicate with others (i.e. intentional communication) and children's language understanding between the measures of social motivation and later expressive language. We tested 87 children with autism spectrum disorder, aged 14-31 months, at four times over 24 months. We found that children with relatively stronger social motivation had relatively better language use 2 years later. This positive link was partly due to a child's ability to produce intentional communication and to understand language. Although we did not measure parents' talking to their children, a theory that inspired this study suggests that children who use frequent intentional communication probably motivate others to talk with them frequently, which facilitates children's language understanding which leads to the development of expressive language. This theory, if confirmed to be true, can provide guidance for parents who want to help their children learn to talk. Parents could look for intentional communication from their children and respond by talking to their children. Effective intervention on both parent and child targets will likely enhance treatment efficacy. Future work is needed to test these ideas.