Regular and Irregular Inflection in Different Groups of Bilingual Children and the Role of Verbal Short-Term and Verbal Working Memory

Bilingual children often experience difficulties with inflectional morphology. The aim of this longitudinal study was to investigate how regularity of inflection in combination with verbal short-term and working memory (VSTM, VWM) influences bilingual children’s performance. Data from 231 typically developing five- to eight-year-old children were analyzed: Dutch monolingual children (N = 45), Frisian-Dutch bilingual children (N = 106), Turkish-Dutch bilingual children (N = 31), Tarifit-Dutch bilingual children (N = 38) and Arabic-Dutch bilingual children (N = 11). Inflection was measured with an expressive morphology task. VSTM and VWM were measured with a Forward and Backward Digit Span task, respectively. The results showed that, overall, children performed more accurately at regular than irregular forms, with the smallest gap between regulars and irregulars for monolinguals. Furthermore, this gap was smaller for older children and children who scored better on a non-verbal intelligence measure. In bilingual children, higher accuracy at using (irregular) inflection was predicted by a smaller cross-linguistic distance, a larger amount of Dutch at home, and a higher level of parental education. Finally, children with better VSTM, but not VWM, were more accurate at using regular and irregular inflection.