The ‘building blocks’ of bird calls resemble those of human languages, new research from the University of Warwick and the University of Zurich has found.
Through analysis of the calls of the chestnut-crowned babbler – a highly social bird from the Australian outback, the researchers claim to have gained new insight into the evolution of human language.
Human languages are comprised of meaningful words, which themselves are built from different combinations of meaningless sounds. This new research into bird calls, or vocalisations, uncovered that they can, like human languages, also be decomposed into perceptibly distinct meaningless sounds, or ‘building blocks’.
Previous research demonstrated that chestnut-crowned babbler calls seemed to be composed of two different sounds ‘A’ and ‘B’ in different arrangements when performing specific behaviours.
When flying, the birds produced a flight call ‘AB’, but when feeding chicks in the nest they emitted ‘BAB’ provisioning calls. In the current study, the authors used playback experiments, previously used to test speech-sound discrimination in human infants, to probe the perception of the sound elements in babblers.
Co-author Professor Simon Townsend of the University of Warwick and University of Zurich said: ‘To our knowledge, this is the first time that the meaning-generating building blocks of a non-human communication system have been experimentally identified.’ He concluded: ‘Although the building blocks in the babbler system may be of a very simple kind, it might still help us understand how combinatoriality initially evolved in humans.’
Commenting on the research, lead author Dr Sabrina Engesser of the University of Zurich said: ‘Through systematic comparisons, we tested which of the elements babblers perceived as equivalent or different sounds. In doing so, we were able to confirm that the calls could be broken up into two perceptually distinct sounds that are shared across the calls in different arrangements.
‘Furthermore, none of comprising elements carried the meaning of the calls confirming the elements are meaningless,’ she added.
‘This system is reminiscent of the way humans use sounds to form meaningful words,’ co-author Prof Andy Russell from the University of Exeter explained.
These findings raise the exciting possibility that the capacity to generate meaning from meaningless building blocks is widespread in animals, but the authors caution there are still considerable differences between such systems and word generation in language.
They emphasise that a focus on the acoustic distinctiveness of sounds in meaningful animal vocalisations offers a promising approach to investigate the building blocks of non-human animal communication systems.
The research, Chestnut-crowned babbler calls are composed of meaningless shared building blocks, is published today by PNAS, and also included researchers from the universities of Macquarie and New South Wales.
Image credit: Chris Tzaros
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