Growth Trajectories of Joint Attention and Play as Predictors for Language in Young Children at Elevated Likelihood for Autism.

This longitudinal study investigated the predictive value of initial level and growth rate of joint attention and play from 10 to 24 months for language abilities of 24-month-old toddlers at elevated likelihood (EL) for autism. (Semi-)structured assessments were used to measure all variables at different timepoints prospectively in younger siblings of children with autism (siblings, n = 48) and children born before 30 gestational weeks (preterms, n = 49). A positive association was found between initial level of play at 10 months and expressive language at 24 months in siblings, but not in preterms. We did not find an association between initial level of play and receptive language. Growth rate of play and initial level and growth rate of joint attention were not related to language abilities in siblings and preterms. Our results indicate that play and expressive language are interrelated, and early play behaviour may contribute to later language. As this association was absent in preterms, they may follow qualitatively different developmental processes. Moreover, future research including different EL-groups is needed to clarify these differential associations. In contrast to previous studies, no association between early joint attention and later language was found. These inconsistent findings warrant further exploration and highlight the importance of exploring alternative aspects of early development, for instance non-social factors, to expand our understanding of language acquisition.