BACKGROUND: Early intervention is recommended for pre-school children with low language. However, few robustly evaluated language interventions for young children exist. Furthermore, in many interventions the theoretical underpinnings are underspecified and the 'active ingredients' of the interventions not tested. This paper presents a quasi-experimental study to test the efficacy and examine the active ingredients of Building Early Sentences Therapy (BEST): an intervention based on usage-based theory designed to support young children to understand and produce two-, three- and four-clause element sentences. BEST manipulates the input children hear to support them to harness the cognitive mechanisms hypothesized in usage-based theories to promote the development of abstract linguistic representations. One such input manipulation is the use of signing alongside verbal input signalling both content and morphology of target sentences.
AIMS: To examine whether (1) BEST is more efficacious than treatment as usual (TAU); and (2) signing of content and morphology is an active ingredient of the intervention.
METHODS & PROCEDURES: A quasi-experimental study recruited children aged 3;5-4;5 years from 13 schools. Schools were assigned to receive either BEST with sign, BEST without sign or TAU. The TAU group received their usual classroom provision. Across arms schools were matched with respect to classroom oral language environment and indices of deprivation. Participants were 48 children (28 boys) with expressive and/or receptive language abilities ≤ 16th centile measured using the New Reynell Developmental Language Scales (NRDLS). Outcomes gathered by researchers blind to treatment arm were NRDLS production and comprehension standard scores and measures of production of targeted sentence structures.
OUTCOMES & RESULTS: Primary outcomes indicate that BEST with sign was significantly more efficacious than TAU with respect to NRDLS production standard score, but not comprehension. The advantage for production was maintained at follow-up. BEST without sign was significantly more efficacious than TAU on measures of targeted vocabulary, sentence structure and morphology. The results from this quasi-experimental study provide evidence for the efficacy of a usage-based intervention on expressive language outcomes for preschool children with low language abilities. There is also evidence to support the inclusion of sign as an active ingredient, and so efforts to train interventionists in its use are worthwhile.
CONCLUSIONS & IMPLICATIONS: Patterns of findings across outcomes suggest signing of content and morphology may support the development of abstract linguistic representations and accelerate language learning. Given these positive results and the scale of this study, a fully powered randomized controlled trial is warranted.
WHAT THIS PAPER ADDS: What is already known on the subject Robust language skills are crucial for positive social, emotional, academic and economic outcomes across the lifespan. There is a paucity of robustly evaluated interventions for preschool children with language difficulties. The development of such interventions is crucial for ameliorating language difficulties and promoting positive educational and psychosocial outcomes. What this study adds to the existing knowledge This paper evaluates BEST, a novel usage-based language intervention targeting children with language difficulties in the early years. Findings indicate that a usage-based intervention is efficacious for treating language difficulties. In particular, BEST benefited expressive language development, bringing benefits to both treated and untreated language structures and improving standard scores. The role of sign as an active ingredient is also supported. Further evaluation is warranted. What are the practical and clinical implications of this work? Findings suggest that BEST may be effective for targeting children who have been identified as having language difficulties. In particular, expressive language may be improved when the intervention is delivered as it was originally manualized, including a signing system to represent content and grammatical morphology. More broadly, these findings also provide preliminary evidence that the use of a signing system does not hinder oral language development in children with language difficulties and may conversely support their expressive language. Future research exploring the role and underpinning mechanisms of sign in language intervention is warranted.