Babies are able to discriminate all the sounds of all languages no matter what part of the world they are from or what language someone may be speaking to them in.
When babies are exposed to new languages, their brains gather the statistics of that language and are able to react thereto language and grow stronger with it. in the experiment that was done, Yankee babies were exposed to Mandarin and were giving an equivalent reaction that babies who were already exposed to Mandarin did. The babies exposed to Mandarin before had shown progress whereas the Yankee babies didn’t show any progress as they were solely exposed to that for a brief amount of your time.