SEPTEMBER 9, 2019
A new study by an international team headed by the University of Zurich sheds light on whether animal vocalizations, like human words, are constructed from smaller building blocks. By analyzing calls of the Australian chestnut-crowned babbler, the researchers have for the first time identified the meaning-generating building blocks of a non-human communication system.
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.