Towards the evolutionary roots of vocal flexibility in primate communication: dynamics of vocal production development and vocal mechanics in a basal nonhuman primate (Microcebus murinus)

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The aim of this project is to explore for the first time the processes underlying vocal flexibility of a highly vocal and phylogenetically basal primate across development. Previous research of our group revealed that the mouse lemur, a phylogenetically basal primate, exhibits an unexpectedly high degree of vocal flexibility in early ontogeny, which decreases in further development. Our project proposes three different and interrelated work packages by which we will address major components of these unexplored processes. The presence and role of babbling and vocal turn-taking during development, as well as potential determinants, modifying vocal output during development, will be assessed by early and dense sampling of vocal production and standardized bioacoustic and videografic behavioral approaches, using a dataset of 26 developing infants and their 13 mothers. Machine learning, including deep neural network approaches, will be applied to investigate the extent to which the dynamics of vocal development and potential rules can be assessed automatically. Excised larynx experiments and related anatomical and MicroCT-studies of the vocal tract as well as high-speed videorecordings of mouth and tongue movements during vocal production will be performed to uncover the mechanics of vocal production and potential biomechanical constraints in vocal flexibility. Integrating of datasets will allow the validation of the respective methods. The project provides an important empirical basis for comparative research on mammalian vocal communication and contributes to unravel the evolutionary roots of vocal flexibility in primate communication as an important building block for the evolution of human speech and language.