Stringing together meaningless sounds to create meaningful signals is a core feature of human language.
Stringing together meaningless sounds to create meaningful signals is a core feature of human language. Investigating whether animals share this basic combinatorial ability has been complicated by difficulties in identifying whether animal vocalizations are made from smaller, meaningless sounds, or building blocks. New research by scientists at the Universities of Zurich, Exeter, Warwick, Macquarie and New South Wales has addressed this question in the calls of the chestnut-crowned babbler (Pomatostomus ruficeps) – a highly social bird from the Australian Outback.
Meaningful calls composed of distinct sounds
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 behaviors. 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. “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,” explains Sabrina Engesser from the University of Zurich, lead author on the study. “Furthermore, none of the comprising elements carried the meaning of the calls, confirming the elements are meaningless,” she adds.
“This system is reminiscent of the way humans use sounds to form meaningful words,” says co-author Andy Russell from the University of Exeter. The research findings, which are published in the journal Proceedings of the National Academy of Sciences, reveal a potential early step in the emergence of the elaborate combinatorial sound system characterizing human language.
Read more at Universities of Zurich
Image: The chestnut-crowned babbler (Pomatostomus ruficeps) examined in the study, that lives in the Australian outback, is a highly social bird. (Credit: Niall Stopford)