Efficiency Matter

Vocabulary gap among children with language delays and their typically developing peers has been addressed and studied for a long time. This gap not only adversely affects developmental trajectory and future academic achievement of children, especially for those who were left behind at an early age, but also would become wider and wider when children apply their vocabulary knowledge into reading and learning. This gap change is also referred as Matthew Effect: the rich get richer and the poor get poorer. To approach a deeper understanding on how to prevent Matthew Effect and provide high quality vocabulary intervention to narrow gap, this study systematically reviewed 31 peer-reviewed studies with 159 effect sizes regarding vocabulary intervention for young children with and without language delays from preschool to first grade. Data sources included ERIC, ProQuest, PsychInfo, PubMed, and Google Scholar from 2000 to December 2018. Besides, high-ranked scholarly journals in special education were used to manually search additional references. Grounded from previous meta-analyses on vocabulary interventions, the current synthesized analyses also explored reviewed studies’ characteristics such as participants’ background, intervention type, intervention duration, intervention delivery, measurement mechanism, research design, and summary effect size. To analyze how effective and efficient the reviewed studies were to improve children’s vocabulary learning, the current study applied random effect model based meta-analysis strategies with R programming to measure the overall effect size across reviewed studies, the associations among learning outcome and research characteristics, and the learning outcome for children with and without language delays respectively. Results indicated that these interventions were moderately effective to improve children’s vocabulary knowledge including children who were having language delays. Certain instructional types and instruments were reinforced such as explicit instructions, targeted word selection, and measurement adoption. In addition, the concern regarding intervention efficiency for gap narrowing and the investigation on gap narrowing measurement were discussed. The results on efficiency suggested that future investigation and teaching implementation should continuously explore how research design, gap change measurement, and word selection could benefit gap narrowing for young children.