In this article, Muñoz explains the pros and cons to being bilingual. Some costs of being bilinguals are that the brain needs to do 2 things at once, and that they tend to produce fewer words. However it does promote cognitive reserve in elderly, and have more efficient monitoring systems (brain).

This article looks in on parents teaching a second language to their toddler which is the ideal time for kids to pick up a second language. 

Bilinguals averaged higher scores in cognitive performance on tests and "better attention focus, distraction resistance, decision-making, judgement and responsiveness to feedback."

Younger you are, the better the linguist you are. Multilingual brain is "nimbler, quicker, better able to deal with ambiguities, resolve conflicts and even resist Alzheimer's disease and other forms of dementia."

Studies show that bilinguals are "smarter" than monolinguals as it improves cognitive skills. Because bilinguals have to switch languages often, it requires one to monitor the environment which constantly keeps the brain active.