Learning starts early

One of the earliest indications was the finding that newborns prefer
their mother’s voice to that of another female.

Newborns also distinguish sentences from their native language from sentences from another language. Passages read in French produced higher sucking rates (as measured by an operant sucking procedure) in French newborns than passages read in Russian

http://www.ehu.es/ehusfera/neurolengua/files/2011/03/Gomez-and-Gerken-2000-TICS.pdf