Much has been assumed about the expected development of vocal sounds that infants produce during the first year of life. Little is known about how infants coordinate various physical systems to produce vocalizations. No theory of early human communicative development has attempted to present a global description of how infants learn to vocalize. This project represents an initial attempt to relate infant vocal development to the domains of speech production: respiration, phonation, resonance, and articulation. The immediate result of this project is the development of visual aids that summarize fundamental relationships between physical development and early vocal development in infants. It is hoped that this project will lay the groundwork for important new tools of early identification for communicative disorders.