Marmoset Monkey Vocal Communication: Common Developmental Trajectories With Humans and Possible Mechanisms

Prelinguistic vocal development in humans occurs through two parallel processes: Sounds change as the vocal apparatus matures and the rate of this maturation is influenced by social feedback from caregivers. Studies of marmoset monkeys reveal that they exhibit developmental processes strikingly similar to early human vocal development and at the same life-history stages. These processes include babbling-like vocal output and roles for both the autonomic nervous system and contingent parental feedback in changing this output into mature-sounding, context appropriate vocalizations. The similarities between the developmental trajectories of vocal behavior in humans and marmoset monkeys are striking both in their form and timing. Thus, given the comparative evidence to date, we conclude that these similarities are products of convergent evolution, possibly the result of selective pressures on both species to evolve a cooperative breeding strategy.