More than half the world learns more than one language as a child. While we in the monolinguistic world might think that has no bearing on success, there turn out to be many benefits to being bilingual or multilingual. To see those benefits, all we have to do is look at children.
The social benefits of speaking multiple languages are obvious; it broadens your social pool to be able to communicate with more people. But there are other benefits that also come to bear during the life of a bilingual child.
First, cognitive effects are being rapidly studied in science, trying to get a hold on what skills bilinguals are more suited for than people who just speak one language. From the outset, those skills seem to be related to considering different points of view, sorting out conflicting information, and disregarding whatever might be irrelevant. This is probably due to the bilingual having to be of “two minds” more often.
They also tend to master grammar conventions earlier than monolinguals, probably because those conventions tend to be very different between certain languages. Whereas the monolingual might not consider grammar until they start making mistakes, bilinguals have to understand grammar just to be able to switch between their languages.
The challenges of raising a bilingual child
Humans are programmed to learn language. For children who are young enough (elementary age or younger), learning another language is just as easy as learning their first language. It’s when the child is older that language learning becomes “work” and less natural.
Today’s parents are often faced with choices in which language a child should study. These are the people who have a dilemma between Spanish (because it’s prevalent in the US) and Mandarin Chinese (because the economy is becoming more dependent on it). The good news is that in order for the child to experience the benefits discussed above, it doesn’t matter which other language they learn.
The challenge is finding other people with which the child can communicate. Not only does this mean peers. It’s been found that a child with parents who speak a different language is not a guarantee that the child will be bilingual. In this case, it seems nature is really more important than nurture.