Infants have the ability to almost effortlessly learn languages It is only half and a year since my three year old son can speak,However ,he can speak four languages. He was brought up by his grandmother in a village in north China before he was two . so it's natural for him to aquire the language there. I took him to Shanghai when he was 2,we usually talk with him in Mandarin,He could understand us but speak in previous language in the begin. soon he speak in Mandarin little by little and speak in previous language occasionally only when he could not find a word in Mandarin to express the meaning .what he what to say. Three month ago, I brought him to visit his aunt who live in a town in Jangsu.Following his cousin ,he played with the kids of neighborhood all day ，he can comunicated with them in Jangsunese.a few days later .. Recently, I found him speak to me in Shanghainese when I pick up him from kindergarten. It a natural process for babys adapt a new environment and learn a new language.