Should Heritage Languages be Incorporated into Interventions for Bilingual Individuals with Neurodevelopmental Disorders?
Objectives: Research syntheses are key when determining evidence-based practices. Previous reviews on this topic were unregistered narrative reviews with methodological weaknesses. Consequently, the purpose of this review was to evaluate the effects of incorporating heritage languages into interventions for bilingual individuals with neurodevelopmental disorders using more systematic methodology and meta-analytic procedures. The quality of research designs was also evaluated.
Methods: This systematic review was registered with the PROSPERO international prospective register of systematic reviews. Procedures used followed PRISMA guidelines. A total of 18 studies met predetermined inclusion criteria (i.e., used an experimental design, implemented an intervention, included individuals with ID, GDD, CDs, and/or ASD who were bilingual, and investigated the effects of languages of instruction). Participant characteristics, interventions delivered, languages of instruction used, and study outcomes were summarized. Study quality was evaluated using the What Works Clearinghouse (WWC) Standards Rating. Effect sizes for studies that met WWC standards were also calculated.
Results: Nine out of 18 studies were conducted with participants with CDs. The other nine studies were conducted with participants with diagnoses of ID, GDD and/or ASD. Findings indicate a small effect favoring interventions that incorporated participants’ heritage languages versus interventions that were delivered solely in the majority language. Additionally, most studies met WWC standards and were found of be of high quality.
Conclusions: Overall, findings support the incorporation of heritage languages of bilingual individuals with neurodevelopmental disorders into interventions. More than half of the studies conducted with participants with CDs favored interventions delivered in participants’ heritage languages, but the same was only found for a third of studies conducted with participants with ID, GDD, and/or ASD. This may be due to a discrepancy in heritage language supports provided to participants. Specifically, 80% of participants with CDs were reported to be receiving some amount of heritage language instruction in school. However, this was only the case for less than 10% of participants with ID, GDD, and/or ASD. Thus, due to previous exposure, participants with CDs may have developed preferences for heritage language instruction and/or been more familiar with receiving formal instruction in heritage languages. Suggestions for future research include assessing social validity, involving stakeholders when designing and implementing interventions, and investigating strategies for overcoming language barriers between therapists and clients.