Predicting lexical density growth rate in young children with autism spectrum disorders.

PURPOSE The purpose of this longitudinal correlational study was to test whether an environmental variable and 4 child variables predicted growth rate of number of different nonimitative words used (i.e., lexical density). METHOD Thirty-five young (age range = 21-54 months) children with autism spectrum disorders (ASD) who were initially nonverbal or low verbal participated in the study. Lexical density was measured at 3 times: at entry into the study as well as 6 months and 12 months after entry into the study. Growth curve analysis was used to test the associations. The predictive value of the putative predictors in the model was tested after controlling for initial expressive language impairment. RESULTS Initial frequency of intentional communication and diversity of object play were predictors of lexical density growth above and beyond initial expressive language impairment (both pseudo R(2)s = .14). CONCLUSIONS Intentional communication and diversity of object play may represent important prelinguistic goals for young children with ASD. These skills not only have been shown to be malleable through treatment, but they also provide a context for linguistic input from others that may facilitate language development.