The Scientific American – Sayuri Hayakawa and Viorica Marian 
The brain’s ability to adapt to its environment explains how we become specialized to the sounds of our native tongue. All infants are born with the ability to discriminate between the speech sounds of different languages, but eventually become tuned to the inputs they hear the most; neural pathways corresponding to native phonemes are strengthened, while those corresponding to foreign sounds are pruned. For bilinguals, this window of “universal” sound processing stays open longer because of their exposure to richer language environments. In other words, the inputs that our brains receive shape how we experience the world around us. (more)