In their first months, most babies begin to make cooing sounds. Some believe infants at this age begin to participate in a “conversation” with parents and caregivers. These early “conversations” primarily consist of cooing sounds back and forth, usually after a feeding or when an infant is contented. These “conversations” may form the basis for later communication patterns.
Locke, J. (1993). The child’s path to spoken language. Cambridge, MA: Harvard University Press.