DeLTA Center - Dr. Jeremy Borjon, IU - "The body and the development of vocal production"
As adults, speaking appears effortless; yet the functional muscle groups involved are many and their interactions complex. Nonetheless, human infants master this control and coordination while their body is rapidly changing. In this talk, I will first discuss the evolutionary foundation for the role of the body in the production of vocalizations by describing my previous work in marmoset monkeys. Call production in marmosets depends on the dynamic control of heart rate and respiration. I demonstrate how their typical cardiorespiratory activity is maintained within a stable range and the production of species-specific contact calls require cardiorespiratory activity to exit this stable range. The control of body movements around these contact calls also appear to be a key part of the mechanisms enabling them. Similarly, to produce the many different and highly complex sounds that will eventually give way to speech, human infants must learn to successfully control and coordinate their body and its internal states. I present new findings on how bodily movements around the production of sounds become more tightly coordinated with the timing of sound onset from 9 to 24 months of age. I will then present initial evidence and hypotheses on the role of body movement coordination in producing more complex speech sounds. I conclude with a consideration of why understanding the body and the control of its internal states is crucial to understanding the development of cognition. I will provide an overview of my future work, which builds on these initial findings and will consider the role of mature social partners and infant directed speech in influencing the internal states relevant to vocalizations and other cognitive achievements such as visual attention.