In looking at the linguistic behavior of preverbal infants, I will describe their conversational abilities during the first four months of life. Obviously, the ability to participate cooperatively in shared discourse is fundamental to social development in general, and particularly to the development of communicative behavior. In a conversation, one person talks, the other listens and then responds, and the cycle is repeated in a “give-and-take” exchange. One can observe verbal conversational behavior in young children, and if one expands one's category of “conversational behavior” to include nonverbal behavior, then one can also observe such conversations in very young preverbal infants. Indeed, adults often appear to engage in conversation with infants. The adult talks, the infant smiles or vocalizes, the adult responds, and the sequence continues. Structurally these conversations closely resemble the response–reinforcer relationship. Rather than functioning to reward or strengthen infant behavior, social reinforcement may function to create a “give-and-take” conversational environment for the adult and infant.

To what degree are infants able to perceive responses from caregivers as contingent stimulation? Does social reinforcement really serve to establish a conversational environment? How can we demonstrate this experimentally? When do infants come to acquire such conversational abilities? The present chapter will be devoted to answering these questions. However, before I discuss conversational interaction between human infants and their caregivers, I will first provide a review of vocal turn-taking behavior in nonhuman primates since there appears to be phylogenetic continuity between the two phenomena.