Effects of developmental language disorder and bilingualism on children ' s executive functioning: A longitudinal study

Background: Children's executive functioning (EF) is often negatively associated with a developmental language disorder (DLD) and positively related to bilingualism. However, both regarding children with DLD and bilingual children, findings are mixed and few studies have investigated the combination of DLD and bilingualism in relation to EF. Aims: This study investigated the effects of DLD and bilingualism on children's EF development. Methods: Monolingual and bilingual children with DLD and typical development (TD; N = 32 in each group) were tested three times with yearly intervals (MAGE = 71 months at time 1). Verbal and visuospatial working memory, selective attention, and inhibition were assessed. Results: Monolinguals and bilinguals with DLD had weak working memory and inhibition skills at each time point compared to TD peers, which could partly be explained by verbal short-term memory limitations. Positive effects of bilingualism emerged when controlling for Dutch vocabulary and morphology skills, and were most pronounced at time 1. Conclusions: Monolinguals and bilinguals with DLD have similar and persistent EF deficits, which are partly secondary to verbal short-term memory weaknesses. Bilinguals performed better on EF than monolinguals when Dutch language knowledge was controlled for. This effect was found regardless of DLD and was most prominent at age 5-6 years.