By one month of age, every child should be showing awareness of sounds, turning (at
least with their eyes) towards voices or rattles. Most babies start making cooing sounds
by three months of age, and make several other different sounds (growling, laughing,
etc). By four months, babies should be able to hold a "conversation" without words
listening when you talk to them, then "talking" back at you. Of course, on any given day,
a baby might be tired, hungry, or just too interested in looking at your earrings or the
lights on the ceiling. …
