For several decades, researchers have been investigating whether bilinguals and monolinguals differ in their linguistic and cognitive abilities. About 50 years ago, it was believed that exposing children to more than one language was dangerous. However, recent studies show that bilingual children have advantages in cognitive development over monolingual children. Among other things, bilingual children outperform monolingual children in executive control tasks. This study investigated the extent to which the linguistic similarity of the two languages spoken by a bilingual child influences executive control.