Newborn-2months:Cries, sudden pitch shifts.Vegetive sounds.Neutral sounds.Looks intently at adult.Turn taking games/vocal behaviour.Follows objects with eyes.Turns, intends to voices.Coos - vowel like sounds.Startle response,
2-4 MonthsStill mostly vowels but few consonants emerge.Begins consonant plus vowel - coo, goo.Some pleasure sounds - mmmmmm.3 months - look in the direction where others are looking.4 months - turn head when hears voices, looks for speaker.