The first years: Milestones and developmental sequences 1.The earliest vocalization are simply the involuntary crying that babies do when they are hungry or comfortable. 2. They distinguish the voice of their mothers and other speakers, and seem to recognize the language that was spoken around their mother before they were bom. 3. babies are capable to hear difference between sounds as similar as "pa" and "ma". They will continue to respond to these differences for a longer period when they hear more than one languages.