Initial MLU Predicts the Relative Efficacy of Two Grammatical Treatments in Preschoolers With Specific Language Impairments

Purpose—We sought to confirm predictions based on past findings that pre-treatment mean length of utterance (MLU) would predict which of two grammatical treatments would best facilitate generalized and maintained grammatical development in preschoolers with specific language impairment (SLI). Method—The participants were 57 preschoolers with specific language impairment (SLI). A randomized group experiment was used. The two grammatical treatments were Broad Target Recasts (BTR) and Milieu Language Teaching (MLT). MLU was assessed at Time 1 in two conversational language samples. Growth rate of productive grammar was quantified using growth curve modeling on the Index of Productive Syntax (IPSyn) from two conversational language samples at each of 6 measurement periods. Results—Predictions were confirmed for children with initially low MLU, but not for children with initially high MLUs. MLT facilitated growth of grammar better than BTR in children who were initially in Brown’s stage I. Effects maintained 5 months after treatment ended.