The first three years: Milestones and developmental sequences 1. The earliest vocalizations 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 aorund their mother before they were born. 3. Babies are capable to hear the difference between sounds as similar as ‘pa’ and ‘ba’. They will continue to respond to these differences for a longer period when they hear more than one languages.