Like humans, marmoset monkey infants vocalize differently from adults. Maturation of vocalizations depends on parental feedback, as well as development of the vocal apparatus and cognitive controls. Teramoto et al. have set those parameters into a Waddington landscape to understand how the developing marmoset acquires the ability to make mature calls. Key to the theoretical approach is the concept of maximum entropy. Although growth in vocal tract length may lower the pitch, other vocalization changes are caused by changes in muscle control. But it is social feedback—the parental response—that determines just when an individual shifts from infant- to adult-style calls. As development progresses, the shape of the Waddington landscape changes, so that sounds that were formerly too difficult to produce become easier to make with maturity.
eLife 10.7554/eLife.20782 (2017).