Abstracts Language, Literature, and Linguistic

Vokale ontogenetische Prozesse bei Fledermausjungtieren. Vom Babbelverhalten bis hin zum Wechselspiel von sozialer und vokaler Komplexität

by Ahana Aurora Fernandez

The human language faculty is a complex system involving key components such as speech, syntax and semantics. Speech is the motor vocal output of language and our main communication modality in daily life. Speech acquisition requires the ability of vocal production learning and is characterized by a pronounced vocal practice behavior called canonical babbling. During canonical babbling, the infant acquires the basic speech subunits by matching the own oral output to the auditory input. Hence, canonical babbling is a prerequisite to acquire the phonetic repertoire of language. So far, babbling behavior appears to be a relatively rare trait in the animal kingdom and even rarer among mammals. In the thesis presented here, I investigated a conspicuous vocal practice behavior, called babbling, in a vocal production learner, the bat species Saccopteryx bilineata. During their ontogeny, pups engaged in a conspicuous eight-week long phase of vocal practice behavior during which pups acquire a part of their adult vocal repertoire through vocal imitation. The main finding of my dissertation shows that S. bilineata pups exhibit a babbling behavior which is characterized by the same features that define human infant canonical babbling. These findings suggest that similar features characterize a distinctive vocal practice phase across vocal production learners, probably arising from similar underlying mechanisms geared toward acquiring adult communication. In human infants, canonical babbling is shaped by vocal and/or behavioral social feedback. In S. bilineata, the pups´ social environment (i.e. the colony) is composed of their mothers, other females with their pups and adult males. The pups´ babbling behavior was accompanied by behaviors and interactions restricted to mother-pup dyads. Adult males produce two song types and provide the main auditory input for pups. My study showed that the social environment influences two main factors of the babbling behavior; the amount of vocal practice and the babbling (i.e. syllabic) composition. The maternal behavior influences the amount of vocal practice, both on a daily level and over the entire ontogeny. Both the mothers´ behavior and the number of singing males present in a colony influenced the babbling bout composition, especially the production of syllable sequences that were mainly composed of song syllables acquired through vocal production learning. This study demonstrates that similar to infant speech development, social feedback influences the babbling behavior in bat pups. A special form of social feedback in humans is the so-called infant-directed speech or "motherese". Infant-directed speech is characterized by universal features (e.g. increased pitch) and, moreover, recent research has shown that the timbre (i.e. the spectral quality of sound) of motherese is distinctly different than the timbre of adult-directed speech in humans. Motherese supports linguistic learning and has social benefits. In non-human animals, pup-directed vocalizations are very common, but so far…