Babbling in a bird shows same stages as in human infants: The importance of the 'Social' in vocal development

Abstract

Over forty years ago Marler asked whether there might be parallels between birdsong and human speech development and, indeed, neuroethological studies have since confirmed important (convergent) similarities between songbirds and humans in brain function for vocal learning. Yet little concrete evidence exists of the behavioural expression of the first stages of vocal development demonstrating similarity between babbling in human infants and songbirds. Uniquely, Australian magpie nestlings and juveniles have been found to incorporate approximations of human speech and words in their early repertoire practice. Because these sounds are clearly identifiable and recognisably different from their species-specific song, this offers a window for discussing mimicry in the context of infant language development. This paper will report and analyse pre-human mimicry segments (i.e. a bird's mimicry of human speech prior to the development of individual and identifiable human words) in early expressions of general vocal practice in nestling and juvenile hand-raised songbirds. The data derived from vocal records demonstrate that phonetic play follows patterns similar to human babbling. This exciting discovery demonstrates that, under certain conditions, the acquisition of song follows stages of phonetic play. These correspond roughly to human language development, and also raise the question of the role of vocal mimicry. This finding perhaps even suggests evolutionary constraints on language acquisition.