Learning a second language is always sensitive, therefore, it is potentially more fertile to learn it at an age at which you are generally more receptive to learning. It is well known that the best age at which to learn language is during babyhood, since, during the early years, the brain is specifically arranged to master a language. However, this is not constrained to any particular tongue; it depends on to what language the infant is exposed.
Thus it follows that an English baby will just as easily learn its native language as a Chinese one. Heavy exposure to any language during a child's first few years should, therefore, ensure comprehension of the language for the rest of their life. This is largely due to the mechanisms by which people learn languages. Children begin to pick up language by imitation; in other words, they repeat noises that they hear in their environment, whether from their parents or from others around them. The noises they make will gradually begin to reflect the tones and phonics of the language or languages to which they are most exposed in their everyday life.
