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)
Human Cognitive and Systems Neuroscience
Final Report Abstract
Humans acquire language by learning to manipulate the vocal apparatus to produce vowels, consonants, words, or sentences. Thus, the ability of vocal plasticity is a basic step for human language evolution. The aim of the project was to investigate the vocal ontogeny and the capacity of vocal plasticity of a vocally active and phylogenetically basal primate, the grey mouse lemur. Since our previous research indicated an unexpectedly high vocal flexibility in early ontogeny, we aimed to investigate the vocal development of the acoustically complex call type trill, not present at birth, until weaning. For the analyses of syllable composition and syntactic rules in infants and adult trill calls, we established detector and classification networks as well as supervised and unsupervised clustering approaches. Further, we aimed to investigate the biomechanics of vocal production as a basic unit of allowing vocal flexibility. To investigate vocal ontogeny during infancy, we analysed audio- and video recordings obtained during standardized experimental paradigms or during sleeping box monitoring for 26 developing infants and their 13 mothers. Our results showed that infant mouse lemurs fulfil six out of seven criteria of animal babbling, namely Universality, Syllable subset acquisition, Independence of the social context, Rhythmic and Repetitive and Babbling bout composition and Facilitating caregiver interactions. Thereby, the syntactic structure of infant vocal bouts gradually resembled the syntactic structure found in adult trills. Interestingly, the first syllable of an infant vocal bout showed also after weaning a higher variability than the syllables produced in the middle or end part of the vocal bout. This suggests a prolonged vocal plasticity even after weaning to manifest individualized vocal signatures. Further, we found that agedependent changes in the acoustic structure of infant vocalizations cannot solely explained by physical maturation. This is also supported by our finding that adult female mouse lemurs show the ability of vocal accommodation to signal sleeping group membership independent of genetic relationship. We developed and provided detector and classification networks which we validated for different call types, individuals and recording qualities. This will allow a timeefficient analyses of longitudinal data important to study the prolonged phase of vocal plasticity. Larynx experiment point that although mouse lemurs produce ultrasonic vocalizations, the vocal production mechanism is more similar to marmoset than to rodents or bats. Thus, our findings contribute to understand the phylogenetic roots of vocal flexibility in primate communication as an important milestone for the evolution of language. Further studies should focus on the persistence and social function of vocal flexibility in adulthood.
Publications
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Utilizing DeepSqueak for automatic detection and classification of mammalian vocalizations: a case study on primate vocalizations. Scientific Reports, 11(1).
Romero-Mujalli, Daniel; Bergmann, Tjard; Zimmermann, Axel & Scheumann, Marina
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From simple to complex: vocal development of the trill call in grey mouse lemurs. EfP-GfP 2022.
Langehennig-Peristenidou A., Romero-Mujalli D. & Scheumann M.
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Variable vocal streams during infancy: ontogeny of the trill call in grey mouse lemurs. ECBB 2022, S. 83–84.
Langehennig-Peristenidou A., Romero-Mujalli D., Bergmann T. & Scheumann M.
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Vocal plasticity during infancy: ontogeny of the trill call in grey mouse lemurs. In: Second Virtual Conference of the Ethologische Gesellschaft e. V. 2022, S. 11.
Langehennig-Peristenidou A., Romero-Mujalli D., Bergmann T. & Scheumann M.
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Dataset: Features of animal babbling in the vocal ontogeny of the gray mouse lemur [Data set]. In Scientific reports (Bd. 13, Nummer 21384). Zenodo.
Langehennig-Peristenidou A. & Scheumann M.
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Features of animal babbling in the vocal ontogeny of the gray mouse lemur (Microcebus murinus). Scientific Reports, 13(1).
Langehennig-Peristenidou, Alexandra; Romero-Mujalli, Daniel; Bergmann, Tjard & Scheumann, Marina
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Maturation of the vocal production system cannot solely explain the acquisition of the adult trill call in infant grey mouse lemurs. Behaviour 2023, S. 185.
Langehennig-Peristenidou A. & Scheumann M.
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Impact of social relationships on adult trill calls in grey mouse lemurs (Microcebus murinus). Annual Meeting of the Ethological Society 2024, S. 14.
Langehennig-Peristenidou A. & Scheumann M.
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Sex differences in the impact of social relationships on individual vocal signatures in grey mouse lemurs ( Microcebus murinus ). Philosophical Transactions of the Royal Society B: Biological Sciences, 379.
Langehennig-Peristenidou, Alexandra & Scheumann, Marina
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Sex differences in the impact of social relationships on individual vocal signatures in grey mouse lemurs [Data set]. In Philosophical Transactions B (Bd. 379, S. 20230193). Zenodo.
Langehennig-Peristenidou A., Romero-Mujalli D., Bergmann T. & Scheumann M.
