Prof. Inbal Arnon answers:
Bilingual babies- those exposed to two languages from birth- may begin speaking slightly later than monolingual babies, but they acquire both languages naturally and reach language development milestones at a similar pace. While their vocabulary in each language may be somewhat smaller than that of their monolingual peers (since they typically hear each language less frequently), they effectively distinguish between the two languages from the start and do not confuse them. They will even notice if you switch languages mid-sentence.
Bilingualism provides numerous long-term benefits, from heightened creativity and problem-solving skills to a protective effect against dementia in later life. Today, there is broad consensus that parents who speak two different native languages should actively speak both languages to their children.
Professor Inbal Arnon is a linguist who has been studying language development in children for over 20 years. She conducts research and teaches at the Hebrew University of Jerusalem and the University of Edinburgh in Scotland.