Abstract. 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 strikingly similar to early human vocal development. These processes include babbling-like vocal output and a role for social feedback in changing this output into mature-sounding vocalizations. My talk will present what we've learned by using marmoset monkeys to investigate the interplay between biomechanical and physiological mechanisms that govern how early vocalizations are produced and how they are shaped by social feedback.