Research has shown that from infancy to age 6 or 7, many new connections are being formed in the brain, and when exposed to the sounds of a second language during this time, the brain of a young child will actually grow connections that make a new language easy to learn. As the brain develops most in the first three years of a person's life, exposing your child to another language during this time actually stimulates the development of brain cells.

Around age 10 to 12, the brain not only begins to slow in its ability to develop those connections, but it starts to prune away any that aren't being used. Thus, children who don't start learning a second language until later in life will often find it more difficult because their brain will not have developed the necessary connections.