The autonomic nervous system is the engine for vocal development through social feedback.

At least one non-human primate species-the marmoset monkey-exhibits developmental processes similar to human vocal development. These processes include babbling-like early vocal output and a role for social feedback in changing this output into mature-sounding vocalizations. Such parallel behaviors provide a window through which we can begin to understand the physiological mechanisms for how early vocalizations are produced and shaped by social feedback. The latest work shows that the acoustic structure of babbling in infant monkeys is driven by oscillations of the autonomic nervous system. It is hypothesized that this autonomic nervous system rhythm is perturbed through vocal interactions between infants and parents. These interactions gradually accelerate the transformation of immature vocalizations into mature forms.