Predictors of treatment response for preschool children with developmental language disorder

Purpose: Enhanced Conversational Recast treatment is an effective intervention for remediating expressive grammatical deficits in preschool-age children with developmental language disorder, but not all children respond equally well. In this study, we sought to identify which child-level variables predict response to treatment of morphological deficits. Method: Predictor variables of interest, including pre-intervention test scores and target morpheme production, age, and mother’s level of education (proxy for socioeconomic status) were included in analyses. The sample included 105 children (M = 5;1 [years;months]) with developmental language disorder who participated in 5 weeks of daily Enhanced Conversational Recast treatment. Classification and regression tree analysis was used to identify covariates that predicted children’s generalization of their trained grammatical morpheme, as measured by treatment effect size d. Results: Our analysis indicates that the Structured Photographic Expressive Language Test–Preschool 2 (SPELT-P 2) scores and the Peabody Picture Vocabulary Test–Fourth Edition scores significantly predicted the degree of benefit a child derived from Enhanced Conversational Recast treatment. Specifically, a SPELT-P 2 score above 75 (but still in the impaired range, < 87) combined with a high Peabody Picture Vocabulary Test–Fourth Edition score (> 100) yielded the largest treatment effect size, whereas a SPELT-P 2 score below 75 predicted the smallest treatment effect size. Other variables included in the model did not significantly predict treatment outcomes. Conclusions: Understanding individual differences in response to treatment will allow service providers to make evidence-based decisions regarding how likely a child is to benefit from Enhanced Conversational Recast treatment and the expected magnitude of the response based on the child’s background characteristics.