Maximizing outcomes for preschoolers with developmental language disorders: testing the effects of a sequentially targeted naturalistic intervention

Between 10-15% of children evidence significant delays or disorders in language development. Persistent language delays during early childhood place children at significant risk for poor academic, behavioral, and social outcomes across the school years and into adulthood. Although brief naturalistic interventions have been shown to increase expressive vocabulary use and reduce behavior problems in toddlers with receptive and expressive language delays in comparison to no treatment comparisons groups, brief intervention is not sufficient to alter developmental trajectories sufficiently to reduce the developmental gaps for young children with both receptive and expressive languages relative to their typically developing peers (Roberts & Kaiser, 2015; Hampton, Kaiser & Roberts, in press). To accelerate language growth over a sustained period of time, language interventions must move beyond interventions that focus on isolated domains (e.g., vocabulary, grammatical morphemes, emergent literacy) and target the critical transition points that exist between domains. By anticipating the challenges children with developmental language disorders often experience at these transition points, we will be able to capitalize on developmental momentum and sustain accelerated language growth relative to children who do not receive intervention aimed at transition points. No studies to date have examined the potential of sustained early intervention for improving language outcomes by using a sequence of treatment targets designed strategically to facilitate the transition from vocabulary to syntax and the transition from language use in highly contextualized activities to more decontextualized activities, ameliorating delays across language domains and potentially reducing the long term risks associated with developmental language disorders. The goal of this Phase I clinical trial is to evaluate the efficacy of a 12-month, intensive language intervention for accelerating language growth and ameliorating early language delays in young children at high risk for persistent developmental language disorders. The proposed hybrid intervention blends an empirically-supported and manualized language intervention process, Enhanced Milieu Teaching (EMT), by adding a psycholinguistically-motivated sequence of treatment targets and promising new input modification strategies (i.e., toy talk; Hadley et al., 2016; Hadley, Rispoli, & Holt, in press). The target population is toddlers with significant delays in receptive and expressive language, typical cognition and no co-morbid conditions. A randomized control trial will compare the effects of the sequential intervention, implemented by parents and therapists, to a community based "business as usual" (BAU) condition. The study will enroll 100 children (M age 30 mos) and their parents. Children assigned to the sequential intervention group (n = 50) will receive 60, 1-hour sessions of direct intervention in the home, and 6 monthly monitoring sessions. Parents will be taught to use EMT procedures and input modification strategies first in play and daily routines, and to adapt these later to dialogic reading activities creating opportunities for supported decontextualized talk. Children will be assessed at seven time points over 18 months to characterize individual growth trajectories for vocabulary and syntax. The primary hypothesis is that growth rates for lexical diversity and sentence diversity will be greater for children in the treatment group compared to the BAU group following the 6-month vocabulary phase (T0-T