Executive Function in Korean-English Bilingual Children with and without Vocabulary Delay

Objectives: The purpose of this study was to investigate whether bilingual children with and without vocabulary delay (BINL and BIVD) show different performance in working memory and shifting, which are subtypes of executive functions. Methods: Thirty-three children (19 normal language group, 14 vocabulary delay group) between 6- and 9-year-old performed Dimensional Change Card Sort (DCCS) as a shifting task, Matrix as a nonverbal working memory task, and Korean and English non-word repetition (NWR) tasks as verbal working memory tasks. For data analyses, one-way ANOVA and Pearson correlation were conducted. Results: The BIVD group performed significantly poorer than the BINL group on DCCS and Matrix, whereas no significant differences on both NWR tasks between groups was observed. The correlation analyses revealed that in the BINL group, both Korean and English composite score of receptive vocabulary were correlated with performance on Matrix and Korean NWR task, and the accuracy and reaction time of DCCS were correlated with each other. On the other hand, in the BIVD group, only Korean composite score of receptive vocabulary showed significant correlation with performance on Matrix and the English NWR task. Conclusion: the BIVD group showed poor performance on both shifting and working memory tasks compared to the BINL group. The results implicate that bilingual children with vocabulary delay have difficulties not only in the language domain but also in the non-linguistic domain. In addition, further investigation on scoring methods of linguistic tasks to bilingual children with vocabulary delay is required to generalize the findings.