Predictors of expressive vocabulary growth in children with autism.

PURPOSE: The purpose of this exploratory study was to examine the variability and predictors of expressive vocabulary development in children with autism and very delayed language. METHOD: This study involved 35 children with autism whose initial chronological ages were between 20 and 71 months and whose initial expressive vocabularies were less than 60 words. Their expressive vocabularies were measured at baseline and at 6, 12, and 24 months following the start of intervention using the MacArthur-Bates Communicative Developmental Inventory (L. Fenson et al., 1993). RESULTS: A cluster analysis revealed 4 distinct patterns of expressive vocabulary development over 2 years. The number of words said, the presence of verbal imitation skills and pretend play skills with objects, and the number of gestures to initiate joint attention at baseline were all associated with the cluster of children who demonstrated the most rapid expressive vocabulary growth over time. The 2 clusters of children who demonstrated the least vocabulary growth had the most significant developmental delays and autism severity at 6 months, but not at baseline. CONCLUSIONS: This study confirms the heterogeneity in language development in young children with autism and, consistent with other reports, confirms that specific prelinguistic skills are predictive of development.