Does bilingualism hamper lexical access in speech production?

In the present study, we tested the hypothesis that bilingualism may cause a linguistic disadvantage in lexical access even for bilinguals' first and dominant language. To this purpose, we conducted a picture naming experiment comparing the performance of monolinguals and highly-proficient, L1-dominant bilinguals. The results revealed that monolinguals name pictures faster than bilinguals, both when bilinguals perform picture naming in their first and dominant language and when they do so in their weaker second language. This is the first time it has been demonstrated that bilinguals show a naming disadvantage in their L1 in comparison to monolingual speakers.