Human vocal development occurs through two parallel processes. First, prelinguistic sounds change as the vocal apparatus matures. Second, parental vocal feedback sensitizes infants to certain features of those sounds and they are modified accordingly. Studies of vocal behavior in marmoset monkeys reveal that they exhibit developmental processes that are strikingly similar: they produce a babbling-like vocal output and the maturation of their vocalizations are facilitated by social feedback from parents. Using this species as a model system, we are now investigating the physiological mechanisms underlying these processes.