The development of motor behaviors, and the influence of energetic and social factors on it, has long been of interest, yet we lack an integrated picture of how these different systems may interact. Through the lens of vocal development in infant marmosets, this study offers a solution for social behavior development by linking motor production with arousal states. Increases in arousal can drive the system out of stochastic states toward oscillatory dynamics ready for communication.

Adult behaviors, such as vocal production, often exhibit temporal regularity. In contrast, their immature forms are more irregular. We ask whether the coupling of motor behaviors with arousal changes give rise to temporal regularity and drive the transition from variable to regular motor output over the course of development. We used marmoset monkey vocal production to explore this putative influence of arousal on the nonlinear changes in their developing vocal output patterns. Based on a detailed analysis of vocal and arousal dynamics in marmosets, we put forth a general model incorporating arousal and auditory-feedback loops for spontaneous vocal production. Using this model, we show that a stable oscillation can emerge as the baseline arousal increases, predicting the transition from stochastic to periodic oscillations occurring in marmoset vocal development. We further provide a solution for how this model can explain vocal development as the joint consequence of energetic growth and social feedback. Together, our model offers a plausible mechanism for the development of arousal-mediated adaptive behavior.