Surprise: Baby marmosets learning to 'talk' do listen to adults

To monitor and measure the vocal development in marmosets, Daniel Takahashi et al. recorded vocalizations between the first day of birth and two months of age, using four well-established acoustic parameters. Recordings were taken during social isolation, as well as during auditory (but not visual) interactions with parents. Adults emit distinct, whistle-like "phees," but infants emit immature sounds such as cries, phee cries, and subharmonic phees.

The team sought to determine whether physical maturation or learning from caregivers was the key mechanism behind the transition from immature phees to the sophisticated phees heard in adults. Using a model and validating it by measuring respiratory activity, the team determined that the transition is at least partly caused by more stable respiration as the marmosets physically mature.

However, by analyzing the ratio of growth to changes in acoustics across the set of infants, they found that physiological growth does not completely explain the cries-to-phees transition. The team then investigated whether parental responses to infant vocalizations affect the timing of the cries-to-phees transition and found a strong correlation, suggesting that the development of marmoset vocalization is dependent on parental vocal feedback.

A Perspective by Daniel Margoliash and Ofer Tchernichovski provides further insights into the role of learned vocalization, both in marmosets and across other species.