Temporal patterns in innate vocalizations as a window into vocal flexibility: a preliminary study of early call rhythms in the songbird Taeniopygia guttata
Alba A. Dias (Universidade de Santiago de Compostela, Spain)
The capacity to learn complex vocalizations through imitation is a trait that humans share with only a handful of other animals. As an essential part of the externalization component of the human faculty of language (FL) insights into the mechanisms and evolution of vocal learning are crucial for our understanding of how speech became possible in our species.1Lately, the wide availability of songbird models has considerably expanded our knowledge of the neurobiological substrate supporting the production, perception and learning of complex vocal signals.2The present contribution attempts to build on recent work on the zebra finch (Taeniopygia guttata) by investigating the temporal patterns or ‘rhythms’ of its innate vocalizations (calls). Although historically most work on this species has focused on its learned song, a number of studies have shown that investigating innate calls can yield powerful insights into the mechanics of vocal flexibility.3,4Here we present preliminary results from a small quantitative study in which we investigated the nature of very early call rhythms in the species, and the changes these undergo across early development. We analysed sound records of 5 juvenile birds using the specialised software Sound Analysis Pro (SAP2011), and measured temporal intervals between calls for the birds’ first documented days of life. We then built histograms to visualise interval frequency, as well as any tendencies observable in the period under investigation. Our preliminary results reflect a possible tendency towards call interval shortening in very early development, which we hypothesise could serve a number of purposes in relation to later song acquisition. In particular, because adult birdsong requires the production of syllables in very rapid succession, our conjecture is that the birds’ early tendency towards faster call production may work as a form of “motor practice” towards the later demands of song. Since the neurobiological substrate for the production of calls and song has been shown to depend on differentiated pathways with distinct evolutionary histories,5this hypothesis could potentially be tested at additional levels. The study raises important questions on the developmental relationship between innate and learned vocalisations in other vocal learning species, and suggest investigating whether the temporal distribution of prelinguistic vocalisations in humans can predict any aspect of subsequent language development.
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