Is the strength of the relation between early parent follow-in input and later child vocabulary size in infant siblings of children with ASD conditional on engagement state and communication disorders?

Abstract

Younger biological siblings of children with autism spectrum disorder (sibs-ASD) are at a heightened risk for developing communication disorders, such as autism spectrum disorder or language impairment. Two strategies that are theoretically motivated as potentially beneficial for sibs-ASD are follow-in comments and providing input in episodes of higher order supported joint engagement (HSJE). But, because the sibs-ASD population is so heterogeneous, it is possible that some sibs-ASD (such as those with communication disorders) may be more reliant on this special kind of input (follow-in comments in HSJE) than other sibs-ASD who can learn language from input in lower support engagement states. Seventy-two sibs-ASD and their caregivers participated, half of whom had a diagnosed communication disorder. There was a significant statistical interaction between follow-in comments in HSJE and communication disorder subgroup predicting later expressive vocabulary; the relation between follow-in comments in HSJE and later expressive vocabulary was only significant for children without communication disorders. These results are contrary to what was predicted. The observed interaction may be explained by decreased variability in later expressive vocabulary in sibs-ASD with communication disorders.