Interaction of bilingualism and Attention-Deficit/Hyperactivity Disorder in young adults.

One hundred and sixty-eight young adult participants were classified as monolingual or bilingual and as having a previously reported clinical diagnosis of ADHD or not to create four groups. All participants completed tests of language proficiency, ADHD ratings, and executive control. Both bilingualism and ADHD are generally associated with poorer vocabulary knowledge, but bilingualism and ADHD are associated with opposite effects on executive control. Consistent with this literature, bilinguals performed more poorly than monolinguals on the vocabulary test but contrary to predictions, the ADHD group performed somewhat better on language ability than the non-ADHD group, attesting to their high functioning status. For the flanker task, both bilinguals and non-ADHD participants showed less cost in performing in the conflict condition than in the baseline condition. For the stop-signal task, ADHD status interfered more with performance by bilinguals than monolinguals, suggesting a greater burden of ADHD on executive function for this group.